Aprilia SX 125 Workshop Manual

SERVICE STATION MANUAL
854196
RX SX 125
SERVICE STATION
MANUAL
RX SX 125
The descriptions and illustrations given in this publication are not binding; While the basic characteristics
as described and illustrated in this manual remain unchanged, aprilia reserves the right, at any time and
without being required to update this publication beforehand, to make any changes to components, parts
or accessories, which it considers necessary to improve the product or which are required for
manufacturing or construction reasons.
Not all versions shown in this publication are available in all countries. The availability of individual models
should be confirmed with the official aprilia sales network.
© Copyright 2008 aprilia. All rights reserved. Reproduction of this publication in whole or in part is
prohibited. aprilia - After-sales service.
aprilia trademark is property of Piaggio & C. S.p.A.
SERVICE STATION MANUAL
RX SX 125
- This manual provides the main information to carry out regular maintenance operations on your vehicle.
- This manual is intended to aprilia Dealers and their qualified mechanics; several concepts have been
deliberately omitted as they are considered unnecessary. As it is not possible to include complete
mechanical notions in this manual, users should have basic mechanical knowledge or minimum
knowledge about the procedures involved when repairing scooters. Without this knowledge, repairing or
checking the vehicle may be inefficient or even dangerous. As the vehicle repair and check procedures
are not described in detail, be extremely cautious so as not to damage components or injure individuals.
In order to optimise customer satisfaction when using our vehicles, aprilia s.p.a. commits itself to
continually improve its products and the relative documentation. The main technical modifications and
changes in repair procedures are communicated to all aprilia Sales Outlets and its International
Subsidiaries. These changes will be introduced in the subsequent editions of the manual. In case of need
or further queries on repair and check procedures, consult aprilia CUSTOMER DEPARTMENT, which
will be prepared to provide any information on the subject and any further communications on updates
and technical changes related to the vehicle.
NOTE Provides key information to make the procedure easier to understand and carry out.
CAUTION Refers to specific procedures to carry out for preventing damages to the vehicle.
WARNING Refers to specific procedures to carry out to prevent injuries to the repairer.
Personal safety Failure to completely observe these instructions will result in serious risk of personal
injury.
Safeguarding the environment Sections marked with this symbol indicate the correct use of the vehicle
to prevent damaging the environment.
Vehicle intactness The incomplete or non-observance of these regulations leads to the risk of serious
damage to the vehicle and sometimes even the invalidity of the guarantee.
INDEX OF TOPICS
CHARACTERISTICS CHAR
SPECIAL TOOLS S-TOOLS
MAINTENANCE MAIN
TROUBLESHOOTING TROUBL
ELECTRICAL SYSTEM ELE SYS
ENGINE FROM VEHICLE ENG VE
ENGINE ENG
POWER SUPPLY P SUPP
SUSPENSIONS SUSP
CHASSIS CHAS
COOLING SYSTEM COOL SYS
BODYWORK BODYW
PRE-DELIVERY PRE DE
INDEX OF TOPICS
CHARACTERISTICS CHAR
RX SX 125 Characteristics
Rules
Safety rules
Carbon monoxide
If you need to keep the engine running while working on the vehicle, please ensure that you do so in
an open or very well ventilated area. Never let the engine run in an enclosed area. If you do work in an
enclosed area, make sure to use a fume extraction system.
CAUTION
EXHAUST EMISSIONS CONTAIN CARBON MONOXIDE, A POISONOUS GAS WHICH CAN CAUSE
LOSS OF CONSCIOUSNESS AND EVEN DEATH.
Fuel
CAUTION
THE FUEL USED TO POWER INTERNAL COMBUSTION ENGINES IS HIGHLY FLAMMABLE AND
MAY BE EXPLOSIVE UNDER CERTAIN CONDITIONS. IT IS THEREFORE RECOMMENDED TO
CARRY OUT REFUELLING AND MAINTENANCE PROCEDURES IN A VENTILATED AREA WITH
THE ENGINE SWITCHED OFF. DO NOT SMOKE DURING REFUELLING OR NEAR FUEL VAPOUR.
AVOID ANY CONTACT WITH NAKED FLAME, SPARKS OR OTHER HEAT SOURCES WHICH MAY
CAUSE IGNITION OR EXPLOSION.
DO NOT ALLOW FUEL TO DISPERSE INTO THE ENVIRONMENT.
KEEP OUT OF THE REACH OF CHILDREN.
Hot components
The engine and the exhaust system components become very hot and remain hot for some time after
the engine has been switched off. Before handling these components, make sure that you are wearing
insulating gloves or wait until the engine and the exhaust system have cooled down.
Coolant
The coolant contains ethylene glycol which, under certain conditions, can become flammable.
When it burns, ethylene glycol produces an invisible flame which however can cause burns.
CAUTION
TAKE CARE NOT TO SPILL COOLANT ONTO HOT ENGINE OR EXHAUST SYSTEM COMPO-
NENTS; THE FLUID MAY IGNITE AND BURN WITH AN INVISIBLE FLAME. WHEN CARRYING
OUT MAINTENANCE, IT IS ADVISABLE TO WEAR LATEX GLOVES. EVEN THOUGH IT IS TOXIC,
COOLANT HAS A SWEET FLAVOUR WHICH MAKES IT VERY ATTRACTIVE TO ANIMALS. NEV-
ER LEAVE THE COOLANT IN OPEN CONTAINERS IN AREAS ACCESSIBLE TO ANIMALS AS
THEY MAY DRINK IT.
CHAR - 7
Characteristics RX SX 125

DO NOT REMOVE THE RADIATOR CAP WHEN THE ENGINE IS STILL HOT. THE COOLANT IS
PRESSURISED AND MAY CAUSE SCALDING.
Used engine oil and transmission oil
CAUTION
IT IS ADVISABLE TO WEAR LATEX GLOVES WHEN SERVICING THE VEHICLE.

THE ENGINE OR GEARBOX OIL MAY CAUSE SERIOUS INJURIES TO THE SKIN IF HANDLED
FOR PROLONGED PERIODS OF TIME AND ON A REGULAR BASIS.
WASH YOUR HANDS CAREFULLY AFTER HANDLING OIL.
HAND THE OIL OVER TO OR HAVE IT COLLECTED BY THE NEAREST USED OIL RECYCLING
COMPANY OR THE SUPPLIER.
DO NOT DISPOSE OF OIL IN THE ENVIRONMENT
Brake and clutch fluid
BRAKE AND CLUTCH FLUIDS CAN DAMAGE THE PLASTIC OR RUBBER PAINTED SURFACES.
WHEN SERVICING THE BRAKING OR THE CLUTCH SYSTEM PROTECT THESE COMPONENTS
WITH A CLEAN CLOTH. ALWAYS WEAR PROTECTIVE GOGGLES WHEN SERVICING THESE
SYSTEMS. BRAKE AND CLUTCH FLUIDS ARE EXTREMELY HARMFUL FOR YOUR EYES. IN
THE EVENT OF ACCIDENTAL CONTACT WITH THE EYES, RINSE THEM IMMEDIATELY WITH
PLENTY OF COLD, CLEAN WATER AND SEEK MEDICAL ADVICE.
Battery electrolyte and hydrogen gas
CAUTION
THE BATTERY ELECTROLYTE IS TOXIC, CORROSIVE AND, AS IT CONTAINS SULPHURIC

ACID, MAY CAUSE BURNING IF IT COMES INTO CONTACT WITH THE SKIN. WHEN HANDLING
BATTERY ELECTROLYTE, WEAR TIGHT-FITTING GLOVES AND PROTECTIVE APPAREL. IN
THE EVENT OF SKIN CONTACT WITH THE ELECTROLYTIC FLUID, RINSE WELL WITH PLENTY
OF CLEAN WATER. IT IS PARTICULARLY IMPORTANT TO PROTECT YOUR EYES BECAUSE
EVEN TINY AMOUNTS OF BATTERY ACID MAY CAUSE BLINDNESS. IN THE EVENT OF CON-
TACT WITH THE EYES, RINSE WITH PLENTY OF WATER FOR FIFTEEN MINUTES AND CON-
SULT AN EYE SPECIALIST IMMEDIATELY. IF THE FLUID IS ACCIDENTALLY SWALLOWED,
DRINK LARGE QUANTITIES OF WATER OR MILK, FOLLOWED BY MILK OF MAGNESIA OR
VEGETABLE OIL AND SEEK MEDICAL ADVICE IMMEDIATELY. THE BATTERY RELEASES EX-
PLOSIVE GASES; KEEP IT AWAY FROM FLAMES, SPARKS, CIGARETTES OR ANY OTHER
HEAT SOURCES. ENSURE ADEQUATE VENTILATION WHEN SERVICING OR RECHARGING
THE BATTERY.
BATTERY LIQUID IS CORROSIVE. DO NOT POUR IT OR SPILL IT, PARTICULARLY ON PLASTIC
COMPONENTS. ENSURE THAT THE ELECTROLYTIC ACID IS COMPATIBLE WITH THE BAT-
TERY BEING ACTIVATED.
Maintenance rules
GENERAL PRECAUTIONS AND INFORMATION
CHAR - 8
When repairing, dismantling and reassembling the vehicle, follow the recommendations given below
carefully.
BEFORE DISASSEMBLING COMPONENTS

• Before dismantling components, remove dirt, mud, dust and foreign bodies from the vehicle.
Use the special tools designed for this bike, as required.
COMPONENTS REMOVAL
• Do not loosen and/or tighten screws and nuts using pliers or any other tools than the specific
wrench.
• Mark the positions on all connection joints (pipes, cables, etc.) before separating them, and
identify them with different distinctive symbols.
• Each component needs to be clearly marked to enable identification during reassembly.
• Clean and wash the dismantled components carefully using a low-flammability detergent.
• Keep mated parts together since they have "adjusted" to each other due to normal wear.
• Some components must be used together or replaced altogether.
• Keep away from heat sources.
REASSEMBLING COMPONENTS
CAUTION
BEARINGS MUST ROTATE FREELY, WITHOUT JAMMING AND/OR NOISE, OTHERWISE, THEY
NEED TO BE REPLACED.
• Only use ORIGINAL Aprilia SPARE PARTS.
• Comply with lubricant and consumables use guidelines.
• Lubricate parts (whenever possible) before reassembling them.
• When tightening nuts and screws, start either from the components with the largest diameter
or from the innermost components, proceeding diagonally. Tighten nuts and screws in suc-
cessive steps before applying the tightening torque.
• Always replace self-locking nuts, washers, sealing rings, circlips, O-rings (OR), cotter pins
and screws with new parts if the thread is damaged.
• When assembling the bearings, make sure to lubricate them well.
• Check that each component is assembled correctly.
• After a repair or routine maintenance, carry out pre-ride checks and test the vehicle on
private grounds or in an area with low traffic.
• Clean all mating surfaces, oil seal rims and gaskets before refitting. Smear a light layer of
lithium-based grease on the oil guard rims. Reassemble oil seals and bearings with the
brand or batch number facing outward (visible side).
ELECTRIC CONNECTORS
Electric connectors must be disconnected as described below; failure to comply with this procedure
causes irreparable damage to both the connector and the wiring harness:
Press the relative safety clips, if applicable.
CHAR - 9
• Grip the two connectors and disconnect them by pulling them in opposite directions.
• If any signs of dirt, rust, moisture, etc. are noted, clean the inside of the connector carefully
with a jet of compressed air.
• Ensure that the cables are correctly fastened to the internal connector terminals.
• Then connect the two connectors, ensuring that they couple correctly (if fitted with clips, you
will hear them "click" into place).
CAUTION
DO NOT DISCONNECT CONNECTORS BY PULLING THE CABLES.
NOTE
THE TWO CONNECTORS CAN ONLY BE CONNECTED IN ONE DIRECTION: CONNECT THEM
THE RIGHT WAY ROUND.
TIGHTENING TORQUES
CAUTION
REMEMBER THAT THE TIGHTENING TORQUES FOR ALL FASTENING ELEMENTS ON WHEELS,
BRAKES, WHEEL AXLES AND ANY OTHER SUSPENSION COMPONENTS PLAY A KEY ROLE
IN ENSURING VEHICLE SAFETY AND MUST COMPLY WITH SPECIFIED VALUES. CHECK THE
TIGHTENING TORQUES OF FASTENING ELEMENTS ON A REGULAR BASIS AND ALWAYS USE
A TORQUE WRENCH TO REASSEMBLE THESE COMPONENTS. FAILURE TO COMPLY WITH
THESE RECOMMENDATIONS MAY CAUSE ONE OF THESE COMPONENTS TO LOOSEN OR
EVEN DETACH, CAUSING A WHEEL TO LOCK OR COMPROMISING VEHICLE HANDLING. THIS
MAY LEAD TO FALLS, WITH THE RISK OF SERIOUS INJURY OR DEATH.
Running-in
Running the engine in correctly is essential for ensuring engine longevity and functionality. Twisty roads
and gradients are ideal for running in the engine, brakes and suspension effectively. Vary your riding
speed during the running in period. This ensures that components operate in "loaded" conditions and
then "unloaded" conditions, allowing the engine components to cool.
CAUTION
THE FULL PERFORMANCE OF THE VEHICLE IS ONLY AVAILABLE AFTER THE SERVICE AT
THE END OF THE RUNNING IN PERIOD.
Follow the guidelines detailed below:
• Do not fully open the throttle grip abruptly at low engine speeds, either during or after the
running in period.
• During the first 100 Km (62 miles) use the brakes gently, avoiding sudden or prolonged
braking. That is to permit the adequate adjustment of the pad friction material to the brake
discs.
Vehicle identification
CAUTION
THE MODIFICATION OF THE IDENTIFICATION CODES IS A SERIOUS PUNISHABLE CRIME.

HOWEVER, THE LIMITED WARRANTY FOR NEW VEHICLES WILL BE VOID IF THE VEHICLE
IDENTIFICATION NUMBER (VIN) HAS BEEN MODIFIED OR NOT PROMPTLY DETERMINED.
CHAR - 10
CHASSIS NUMBER
The chassis number is stamped on the right side
of the headstock.
ENGINE NUMBER
The engine number is stamped on the rear side,
next to the shock absorber.
Dimensions and mass
DIMENSIONS
SIZES SX 125 RX 125
Maximum length 2165 mm (82.24 in) 2255 mm (88.78 in)
Max. width (to brake levers) 850 mm (33.46 in) 850 mm (33.46 in)
Max. height (to mirrors) 1390 mm (54.72 in) 1415 mm (55.71 in)
Saddle height 870 mm (34.25 in) 925 mm (36.42 in)
Wheelbase 1480 mm (58.27 in) 1480 mm (58.27 in)
Minimum ground clearance 260 mm (10.24 in) 300 mm (11.81 in)
Engine
ENGINE
Specification Desc./Quantity
Type single-cylinder, 2-stroke, with reed intake. Separate lubrication
with automatic mixer with variable value (1.0 - 3.0 %).
Cylinder quantity 1
Overall engine capacity 124.82 cm³ (7.616 cu.in)
Bore/stroke 54 - 54.5 mm (2.12 - 2.14 in)
Compression ratio 12.5 +/- 0.5 :1
Squish 1.5 mm (0.06 in)
Engine revs at idle speed 1250 +/- 100 rpm
Engine revs at maximum speed 11000 ± 100 rpm
Ignition CDI with electronic timing
Ignition starter
Clutch multiple-disk, oil-bathed clutch with hand control on the left side
of the handlebar.
Cooling Coolant
Lubrication system Separate lubrication with automatic mixer with variable value
(1.0 - 1.3 %).
CHAR - 11
GEAR
Type mechanic, 6 gear with pedal lever on the left hand side of the
engine
Gear lubrication Splash lubrication
Transmission
TRANSMISSION
TRANSMISSION SX 125 RX 125
Gear ratio 19/63 = 1 :3.316 19/63 = 1 :3.316
1st gear ratio 10/30 = 1:3.000 10/30 = 1:3.000
2nd gear ratio 14/29 = 1:2.071 14/29 = 1:2.071
3rd gear ratio 17/27 = 1:1.588 17/27 = 1:1.588
4th gear ratio 19/25 = 1:1.316 19/25 = 1:1.316
5th gear ratio 21/23 = 1:1.095 21/23 = 1:1.095
6th gear ratio 22/21 = 1:0.954 22/21 = 1:0.954
Final gear ratio (11 kW ) 16/45 = 1:2.812 16/49 = 1:3.062
Final gear ratio (full power ) 15/45 = 1:3.600 15/49 = 1:3.267
Capacities
CAPACITY
CAPACITY SX 125 RX 125
Fuel (reserve included) 10 l (2.20 UKgal) 10 l (2.20 UKgal)
Fuel reserve 3 l (0.66 UKgal) 3 l (0.66 UKgal)
Gearbox oil 600 cm³ (36.61 cu.in) 600 cm³ (36.61 cu.in)
Mixer oil (reserve included) 1 l (0.22 UKgal) 1 l (0.22 UKgal)
Mixer oil reserve 0.25 l (0.055 UKgal) 0.25 l (0.055 UKgal)
Fork oil 400 cm³ (24.41 cu.in) 400 cm³ (24.41 cu.in)
Fork oil level depth from the rim (spring not inclu- 150 mm (5.90 in) 150 mm (5.90 in)
ded; the whole fork comprised)
Coolant (50% H2O + 50% ethylene glycol anti- 0.8 l (0.17 UKgal) 0.8 l (0.17 UKgal)
freeze fluid)
Seats 2 2
Kerb weight (full tank) 126 kg (277.8 lb) 126 kg (277.8 lb)
Scooter max load (rider + passenger + luggage) 336 kg (740.7 lb) 336 kg (740.7 lb)
Electrical system
IGNITION
IGNITION SX 125 RX 125
IGNITION Electronic Electronic
Ignition advance CDI CDI
SPARK PLUG
SPARK PLUG SX 125 RX 125
Standard NGK BR8ES NGK BR8ES
Full Power NGK BR10EG NGK BR10EG
Spark plug electrode gap 0.7 - 0.8 mm (0.027 - 0.031 in) 0.7 - 0.8 mm (0.027 - 0.031 in)
ELECTRICAL SYSTEM
ELECTRICAL SYSTEM SX 125 RX 125
Battery YUASA YUASA
fuses 20A - 15A - 7.5A 20A - 15A - 7.5A
CHAR - 12
ELECTRICAL SYSTEM SX 125 RX 125

(Permanent magnet) Generator 12V - 180W 12V - 180W
BULBS
BULBS SX 125 RX 125
License plate bulb 5W 5W
Rear tail light /stop light led led
Front tail bulb 2V x 3W 2V x 3W
Front/rear turn indicator bulbs 4 x 10W 4 x 10W
Low-/high-beam light bulb HS1 HS1
WARNING LIGHTS
Warning lights SX 125 RX 125
Engine oil level warning light LED LED
High-beam warning light LED LED
Gear in neutral warning light LED LED
Turn indicator warning light LED LED
Frame and suspensions
CHASSIS
CHASSIS SX 125 RX 125
Type Framework with double cradle and Framework with double cradle and
high-resistant steel tubes high-resistant steel tubes
Steering inclination angle 28° 28°
Trail 102 mm (4.02 in) - suspensions fully 113 mm (4.45 in) - suspensions fully
extended extended
Size "A" 555 mm (21.85 in) 555 mm (21.85 in)
Size "B" 459 mm (18.07 in) 459 mm (18.07 in)
SUSPENSIONS
SUSPENSIONS SX 125 RX 125
Front Upside-down with Ø 40-mm (1.57 in) stems Upside-down with Ø 40-mm (1.57 in) stems
Front suspension travel 260 mm (10.24 in) 260 mm (10.24 in)
Rear single gas shock absorber single gas shock absorber
Rear suspension travel 265 mm (10.43 in) 265 mm (10.43 in)
Brakes
BRAKES
BRAKES SX 125 RX 125
Front brake Disc brake, Ø 260-mm (10.24 in) with Disc brake, Ø 260-mm (10.24 in) with
control control
Rear brake Disc brake, Ø 220-mm (8.66 in) with Disc brake, Ø 220-mm (8.66 in) with
control control
CHAR - 13
Wheels and tyres
WHEEL RIMS
WHEEL RIMS SX 125 RX 125
Front 3.00/17" 1.6/21"
Rear 4.25/17" 2.15/18"
TYRES
TYRES SX 125 RX 125
Type Radial Radial
Front 110/70 R17 M/C 54H TL 90/90 - 21 54R MT 21
Rear 150/60 R17 M/C 66H TL 120/90 - 18 65R MT 21
front (rider only) 1.8 bar (180 kPa; 26.11 PSI) 1.4 bar (140 kPa; 20.30 PSI)
rear (rider only) 1.8 bar (180 kPa; 26.11 PSI) 1.6 bar (160 kPa; 23.21 PSI)
front (rider + passenger) 2.0 bar (200 kPa; 29.00 PSI) 1.5 bar (150 kPa; 21.75 PSI)
rear (rider + passenger) 1.8 bar (180 kPa; 26.11 PSI) 1.4 bar (140 kPa; 20.30 PSI)
Supply
FUEL SUPPLY
FUEL SUPPLY SX 125 RX 125
Carburettor model Dell'Orto VHST 28 CD Dell'Orto VHST 28 CD
Fuel Premium unleaded petrol Premium unleaded petrol
Tightening Torques
CHASSIS
Name Torque in Nm
Upper saddle pillar retainer - M8x30 (2) 25 Nm (18.44 lbf ft)
Lower saddle pillar retainer - M8x25 (2) 25 Nm (18.44 lbf ft)
Engine upper plate to chassis retainer - M8x20 (2) 25 Nm (18.44 lbf ft)
Chain tightener roller retainer - M8x60 (1) 25 Nm (18.44 lbf ft)
FOOTRESTS
Name Torque in Nm
Passenger footrest support to saddle pillar retainer - M8x20 (4) 25 Nm (18.44 lbf ft)
Rider footrest support to chassis retainer - M8x45 (2) 25 Nm (18.44 lbf ft)
STAND
Name Torque in Nm
Stand retainer (1) 10 Nm (7.37 lbf ft)
Stand retainer - M10x1.25 lower nut (1) 30 Nm (22.13 lbf ft)
SWINGARM
Name Torque in Nm
Chain guide slider retainer to the fork (1) 5 Nm (3.69 lbf ft)
Chain eye retainer (2) 10 Nm (7.37 lbf ft)
Chain set screw - M8 lower nut (2) 25 Nm (18.44 lbf ft)
Fork pin retainer - M14x1.5 lower nut (1) 80 Nm (59 lbf ft)
Crankcase chain retainer - M5x12 TBEI screw (2) 5 Nm (3.69 lbf ft)
FRONT SUSPENSION
Name Torque in Nm
Upper plate retainer - M8x35 (2) 25 Nm (18.44 lbf ft)
CHAR - 14
Name Torque in Nm
Lower plate retainer - M6x30 (4) 10 Nm (7.37 lbf ft)
Foot lock on wheel pin - M6x25 (2) 10 Nm (7.37 lbf ft)
Bearing pack ring nut preloading (1) 17 Nm (12.54 lbf ft)
Bearings pack ring nut (1) 7 Nm (5.16 lbf ft)
Fork cap (1) 80 Nm (59 lbf ft)
REAR SUSPENSION
Name Torque in Nm
Shock absorber upper retainer - TCEI M10x55 screw (1) 50 Nm (36.9 lbf ft)
Single connecting rod to chassis attachment retainer - TCEI 85 Nm (62.7 lbf ft)
M12x107 screw (1)
Double connecting rod to single connecting rod retainer - TE 50 Nm (36.9 lbf ft)
M10x61 screw (3)
ENGINE
Name Torque in Nm
Engine upper plate to engine retainer - TCEI M8x80 screw (1) 25 Nm (18.44 lbf ft)
Gear shift lever retainer - TCEI M6x20 screw (1) 10 Nm (7.37 lbf ft)
Engine front retainer - TCEI M10x130 screw (1) 50 Nm (36.88 lbf ft)
Engine rear retainer - TCEI M8x60 screw (1) 25 Nm (18.44 lbf ft)
Pinion protection case retainer - TCEI M8x60 screw (2) 25 Nm (18.44 lbf ft)
Solenoid retainer - TE M6x30 screw (1) 10 Nm (7.37 lbf ft)
Coil to chassis retainer - TE M6x40 screw (2) 10 Nm (7.37 lbf ft)
FILTER CASING
Name Torque in Nm
Filter half-housing retainer (7) 3 Nm (2.2 lbf ft)
Filter cover retainer (4) 3 Nm (2.2 lbf ft)
Filter housing to saddle pillar upper retainer (1) 6 Nm (4.42 lbf ft)
Filter casing / mudflap to saddle pillar lower retainer (2) 6 Nm (4.42 lbf ft)
SAS valve to chassis / horn retainer - TE M6x12 screw (2) 10 Nm (7.37 lbf ft)
EXHAUST SYSTEM
Name Torque in Nm
Muffler retainer - TE M6x16 screw (1) 10 Nm (7.37 lbf ft)
Intermediate pipe retainer - TE M6x12 screw (1) 10 Nm (7.37 lbf ft)
Protection retainer - TE M6x12 screw (2) 10 Nm (7.37 lbf ft)
Silencer support bracket retainer - TE M6x16 screw (2) 10 Nm (7.37 lbf ft)
Silencer retainer - TCEI M6x16 screw (1) 10 Nm (7.37 lbf ft)
Silencer support retainer - TE M6x16 screw (2) 10 Nm (7.37 lbf ft)
COOLING SYSTEM
Name Torque in Nm
Radiator to chassis retainer - TE M6x25 screw (6) 10 Nm (7.37 lbf ft)
FRONT WHEEL
Name Torque in Nm
Wheel pin retainer (1) 80 Nm (59 lbf ft)
Brake disc retainer - TSPEI M8x16 screw (6) 25 Nm (18.44 lbf ft) - Loctite 243
REAR WHEEL
Name Torque in Nm
Rear wheel pin retainer - M16x1.5 nut (1) 100 Nm (73.75 lbf ft)
Brake disc retainer - TSPEI M6x16 screw (6) 10 Nm (7.37 lbf ft) - Loctite 243
Crown retainer - TSPEI M8x26 screw (6) 25 Nm (18.44 lbf ft) - Loctite 243
Speed sensor support plate retainer - TE M6x12 screw (2) 10 Nm (7.37 lbf ft)
Speed sensor retainer - TE M6x16 screw (1) 10 Nm (7.37 lbf ft)
CHAR - 15
FRONT BRAKE
Name Torque in Nm
Front brake calliper to fork feet retainer - TE M8x30 screw (2) 25 Nm (18.44 lbf ft)
Front brake pipe to stem protection retainer - TE M5x16 screw 5 Nm (3.69 lbf ft)
(2)
Front brake pipe to stem protection retainer - M5 nut (2) 5 Nm (3.69 lbf ft)
REAR BRAKE
Name Torque in Nm
Rear brake pump to chassis retainer - TE M6x16 screw (2) 10 Nm (7.37 lbf ft)
Rear brake lever retainer - TCEI M8x50 screw (1) 25 Nm (18.44 lbf ft)
Rear brake calliper to support retainer - TE M8x20 screw (2) 25 Nm (18.44 lbf ft)
Brake pipe to fork retainer - TE M5x16 screw (2) 5 Nm (3.69 lbf ft)
HANDLEBAR AND CONTROLS

Name Torque in Nm
Front brake pump retainer- TCEI M6x25 screw (2) 10 Nm (7.37 lbf ft)
Clutch control retainer - TCEI M5x15 screw (2) 5 Nm (3.69 lbf ft)
Handlebar U-bolts - TE M7x35 screw (4) 18 Nm (13.28 lbf ft)
Throttle control - TCEI M5x15 screw (2) 5 Nm (3.69 lbf ft)
Throttle control cover - M4x9 screw (2) 3 Nm (2.21 lbf ft)
Left light switch - screw (2) 1.5 Nm (1.1 lbf ft)
ELECTRICAL COMPONENTS
Name Torque in Nm
Control unit retainer - screw (2) 5 Nm (3.69 lbf ft)
Regulator to mudflap retainer - TE M6x30 screw (2) 10 Nm (7.37 lbf ft)
LIGHTS / INSTRUMENT PANEL

Name Torque in Nm
Instrument panel retainer - M5 nut (3) 5 Nm (3.69 lbf ft)
Front light retainer - TBEI M6x20 screw (2) 10 Nm (7.37 lbf ft)
Rear light retainer - screw (2) 3 Nm (2.21 lbf ft)
Front turn indicators retainer - TBEI M6x20 screw (2) 10 Nm (7.37 lbf ft)
Rear turn indicators retainer - TBEI M6x20 screw (2) 10 Nm (7.37 lbf ft)
License plate retainer - screw (1) 3 Nm (2.21 lbf ft)
TANK
Name Torque in Nm
Fuel cock to tank retainer - TE M6x12 screw (2) 7 Nm (5.16 lbf ft)
Tank retainer - TE M6x30 screw (2) 10 Nm (7.37 lbf ft)
BODYWORK
Name Torque in Nm
Mudflap to saddle pillar retainer - TBEI M5x16 screw (2) 5 Nm (3.69 lbf ft)
License plate holder / mudflap to saddle pillar retainer - TE 7 Nm (5.16 lbf ft)
M6x16 screw (4)
Tail to right/left tail section retainer - TBEI M5x9 screw (2) 5 Nm (3.69 lbf ft)
Tail to right/left tail section retainer - screw (2) 3 Nm (2.21 lbf ft)
Tail section / fairing to saddle pillar retainer - TE M5x25 screw 5 Nm (3.69 lbf ft)
(2)
rh/lh fairing front retainer - TE M5x16 screw (2) 5 Nm (3.69 lbf ft)
Fairing to mudflap retainer - TBEI M5x10 screw (2) 5 Nm (3.69 lbf ft)
Fork protection guide retainer - TE M5x20 screw (2) 5 Nm (3.69 lbf ft)
Fork protection retainer - TE M5x12 screw (6) 5 Nm (3.69 lbf ft)
Shock absorber protection to mudflap retainer - TE M6x20 10 Nm (7.37 lbf ft)
screw (2)
Front mudguard to lower plate retainer - TE M6x16 screw (4) 7 Nm (5.16 lbf ft)
Tie rods to front mudguard retainer - TBEI M5 screw (2) 5 Nm (3.69 lbf ft)
Tie rods to front mudguard retainer - M5x20 screw (2) 5 Nm (3.69 lbf ft)
CHAR - 16
Name Torque in Nm
Instrument panel support / tank to upper plate retainer - TCEI 10 Nm (7.37 lbf ft)
M6x30 screw (1)
Tank cover to chassis retainer - TE M6x30 screw (1) 10 Nm (7.37 lbf ft)
Tank cover to tank retainer - TBEI M5 screw (2) 5 Nm (3.69 lbf ft)
Rh/ Lh deflector brackets to radiator system retainer - TBEI 5 Nm (3.69 lbf ft)
M5x9 screw (2)
Rh/ Lh deflector bracket to radiator systems retainer - TCB 3 Nm (2.21 lbf ft)
M4x16 screw (2)
Rh/ Lh deflector to chassis retainer - TBEI M5x9 (2) screw 5 Nm (3.69 lbf ft)
Rh/ Lh deflector to tank front retainer - TE M5x25 (2) screw 5 Nm (3.69 lbf ft)
Rh/ Lh chassis cover retainer - TBEI M5x12 (2) screw 5 Nm (3.69 lbf ft)
FINISHINGS
Name Torque in Nm
Saddle lock tongue retainer - screw (1) 3 Nm (2.21 lbf ft)
Switch retainer - TCEI M8x16 screw (1) 25 Nm (18.44 lbf ft)
Switch - shear head screw retainer (1) Manual
Recommended products chart
LUBRICANTS CHART
Product Description Specifications
Agip GEAR SYNTH, SAE 75W - 90 Gearbox oil As an alternative for recommended oils,
use top branded oils that meet or exceed
the API GL - 4 requirements.
AGIP FORK 7.5W Recommended FORK OIL If you intend to have an intermediate per-
formance, as an alternative to the recom-
mended AGIP FORK 5W or AGIP FORK
20W use:
AGIP FORK 7.5W
AGIP FORK 10W
AGIP FORK 15W
AGIP SPEED 2T Mixer oil As an alternative for recommended oils,
use top branded fully synthetic oils that
meet or exceed the ISO - L - EGD, JASO
FC or API TC specifications require-
ments.
AGIP GREASE SM 2 Grease for C-ring of the tone wheel Soap-based lithium grease with NLGI 2
molybdenum disulphide; ISO-L-
XBCHB2, DIN KF2K-20
NEUTRAL GREASE OR PETROLEUM Battery poles Neutral grease or petroleum jelly.
JELLY
AGIP CHAIN GREASE SPRAY Chain spray grease -
AGIP BRAKE 4 / BRAKE 5.1 Recommended BRAKE FLUID -
CHAR - 17
INDEX OF TOPICS
SPECIAL TOOLS S-TOOLS

RX SX 125 Special tools
SPECIAL TOOLS
Stores code Description
AP0277215 Buffer for fitting oil seal 250455
AP0277970 Guide bushing for oil seal 930675
AP0876973 Piston ring clamp 54 mm
S-TOOLS - 19
Special tools RX SX 125

AP0276040 Clutch wrench 11 mm
AP0277180 Bearing tie rod kit
AP0277455 Extractor plate to separate the crankcase

halves
AP0276380 bolt M10
AP0276370 Split bushing
AP0242091 Hexagon nut M10
AP0276382 Bolt
S-TOOLS - 20

AP0242700 Flanged nut M8
AP0277445 Guillotine extractor
AP0277917 Brackets
AP0276025 Half-ring
AP0977490 Ring for half-rings
AP0876298 Extractor for crankshaft bearings
S-TOOLS - 21
Special tools RX SX 125

AP0840681 Allen screw for extractor M8x40
AP8146486 Front service stand
AP8140192 Chain fitting kit
AP8140180 Extractor for bushings
AP8705021 Rear service stand
AP8140204 Supports for rear service stand
AP8140199 Tool panel
S-TOOLS - 22

AP8101945 Fork pin ring nut
S-TOOLS - 23
INDEX OF TOPICS
MAINTENANCE MAIN
RX SX 125 Maintenance
Maintenance chart
SX RX 125 ROUTINE MAINTENANCE TABLE

I: INSPECT AND CLEAN, ADJUST, LUBRICATE OR REPLACE IF NECESSARY
C: CLEAN, R: REPLACE, A: ADJUST, L: LUBRICATE
* Replace every year
** Replace every 2 years
*** Replace every 4 years
**** Lubricate the chain every 500 km (310.98 mi)
km x 1,000 1 4 8 12 16 20 24 28 32 36 40
Rear shock absorber I I I I I
Battery / terminal tightening I I I I I I I I I I I
Spark plug I I R I R I R I R I R
Carburettor, idle speed A I A I A I A I A I A
Transmission cables and controls I I I I I I I I I I
Rave (FULL POWER) control unit I A A A A A
Wheel centring I I I I I I I I I I I
Steering bearings and steering clearance I I I I I I I I I I I
Wheel bearings I I I I I I I I I I I
Brake discs I I I I I I I I I I I
Air filter I I R I R I R I R I R
Mixer oil filter C C C C C
Vehicle general operation I I I I I I I I I I I
Clutch clearance A A A A A A A A A A A
Light circuit I I I I I I I I I I I
Cooling system I I I I I I I I I I I
Braking systems I I I I I I I I I I I
Brake fluid * I I I I I I I I I I I
Mixer oil level I I I I I I I I I I I
Coolant ** I I I I I I I I I I I
Muffler / exhaust silencer I I I I I I I I I I
Fork oil and oil seal **
Gearbox oil R I I R I I R I I R I
Front headlight aiming A A A A A A A A A A A
Start-up lever bolt I I I I I I I I I I I
Piston and compression rings I R I R I
Mixer pump and air bleeding I A A A A A
WHEELS AND TYRES I I I I I I I I I I I
Bolts and nuts tightening I I I I I I I I I I I
Mixer oil reserve warning light I I I I I I I I I I I
Final drive unit (chain, crown, pinion)**** I I I I I I I I I I I
Fuel pipes *** I I I I I I I I I I
Braking system pipes*** I I I I I I I I I I
Mixer oil pipes*** I I I I I I I I I I
Clutch wear I I I I I I I I I I
Brake pads wear I I I I I I I I I I
Outlet valve (FULL POWER) I I I I I I I I I I I
Spark plug
• Remove the spark plug regularly, clean off carbon scales and replace spark plug if neces-
sary.
CAUTION
BEFORE CARRYING OUT THE FOLLOWING OPERATIONS AND IN ORDER TO AVOID BURNS,
LEAVE THE ENGINE AND MUFFLER TO COOL OFF TO AMBIENT TEMPERATURE.
MAIN - 25
Maintenance RX SX 125
• Take out the spark plug tube.

• Remove the spark plug with the sup-
plied wrench.
Gearbox Oil
Inspection
NOTE
PARK THE VEHICLE ON SAFE AND LEVEL GROUND.
• Stop the engine and let it cool off for at least ten minutes so that the oil in the crankcase
flows down and cools as well.
• Keep the vehicle upright with both wheels on the ground.
FAILURE TO FOLLOW THESE OPERATIONS MAY RESULT IN AN INCORRECT READING OF

THE ENGINE OIL LEVEL.
• Make sure the oil level covers the
checking sight glass (1) completely.
TOPPING-UP
If necessary, top up:
• Unscrew and remove the filler plug (2).

• Pour a small amount of oil and wait about a minute until the oil flows evenly into the crank-
case.
• Make sure the oil level covers the sight glass (1) completely.
• If that does not occur, top-up again with small quantities of oil until the recommended level
is reached by checking through the sight glass (1).
• At the end of the operation, screw and tighten the filler plug (2).
MAIN - 26
TIGHTEN UP THE FILLER CAP AND MAKE SURE THE OIL DOES NOT SEEP.
CHECK REGULARLY THAT THERE ARE NO LEAKS IN THE CRANKCASE COVER GASKET.
DO NOT RIDE THE VEHICLE WITH INSUFFICIENT LUBRICATION OR WITH CONTAMINATED OR
INCORRECT LUBRICANTS AS THIS ACCELERATES THE WEAR AND TEAR OF THE MOVING
PARTS AND CAN CAUSE IRRETRIEVABLE DAMAGE.
Replacement
• Start the engine and let it idle for a few minutes; in this way, it is easier to drain the oil during
the subsequent drainage stage.
CAUTION
PARK THE MOTORCYCLE ON SAFE AND LEVEL GROUND.

• Shut off the engine.
OIL BECOMES VERY HOT WHEN THE ENGINE IS HOT; BE CAREFUL NOT TO GET BURNED
WHEN CARRYING OUT THE OPERATIONS DESCRIBED BELOW.
• Keep the vehicle upright with both
wheels on the ground.
• Place a container with suitable capaci-
ty under the drainage plug (2).
• Unscrew and remove the drainage
plug (2).
• Unscrew and remove the filler plug (1).
• Drain the oil into the container; allow
several minutes for oil to drain out com-
pletely.
• Remove any metal scrap attached to
the drainage plug (2) magnet.
• Check and if necessary, replace the
drainage plug (2) sealing washer.
• Screw and tighten the drainage plug
(2).
• Pour gearbox oil through the filler
opening (1).
Characteristic
Gearbox oil
600 cm³ (36.61 cu.in)
MAIN - 27
• Screw the filler plug (1).

• Start the engine and let it idle for about a minute to allow the gearbox oil circuit to get filled.
• Check the oil level and refill if necessary.
TIGHTEN UP THE FILLER CAP AND MAKE SURE THE OIL DOES NOT SEEP.
CHECK REGULARLY THAT THERE ARE NO LEAKS IN THE CRANKCASE COVER GASKET.
DO NOT RIDE THE VEHICLE WITH INSUFFICIENT LUBRICATION OR WITH CONTAMINATED OR
INCORRECT LUBRICANTS AS THIS ACCELERATES THE WEAR AND TEAR OF THE MOVING
PARTS AND CAN CAUSE IRRETRIEVABLE DAMAGE.
Air filter
• Remove the right side central fairing.

• Undo and remove the 4 screws and re-
move the filter casing side cover.
• Remove the filtering element together

with the mesh.
• Wash the filtering element with clean,
non-flammable or high-volatility sol-
vents, and let it dry properly.
• Apply filter oil or heavy oil (SAE 80W -
90) all over the whole surface and then
wring the filtering element to eliminate
excess oil.
THE FILTERING ELEMENT MUST BE WELL IMPREGNA-

TED BUT SHOULD NOT DRIP.
• Clean the air filter more frequently if the vehicle is used on dusty or wet roads.
• In this case, the air filter can be partially cleaned after such a ride.
AIR FILTER PARTIAL CLEANING DOES NOT EXCLUDE OR POSTPONE REPLACING THE FIL-
TER.
MAIN - 28
Cooling system
Level check
Check and top-up

CAUTION
WAIT FOR THE ENGINE TO COOL DOWN BEFORE CHECKING OR TOPPING-UP THE COOLANT
LEVEL.
• Shut off the engine and wait until it
cools off.
• Park the vehicle on firm and level
ground.
• Keep the vehicle upright with the two
wheels on the ground.
• Turn the radiator cap (1) anticlockwise
just one click.
• Wait a few seconds so that possible
pressure in the circuit may be purged.
• Turn the radiator cap (1) anticlockwise
again and remove it.
• Make sure the fluid covers the radiator
plates completely.
CAUTION
DO NOT ADD ADDITIVES OR OTHER SUBSTANCES TO

THE FLUID.
WHEN USING A FUNNEL OR ANY OTHER ELEMENT,
MAKE SURE IT IS PERFECTLY CLEAN.
CAUTION
COOLANT IS TOXIC IF INGESTED; CONTACT WITH YOUR

EYES OR SKIN MAY CAUSE IRRITATION. DO NOT INTRO-
DUCE YOUR FINGERS OR ANY OTHER OBJECT TO
CHECK IF THERE IS COOLANT OR NOT.
Braking system
MAIN - 29
Top-up
• The following operations refer to one

braking system but they are valid for
both braking systems:
1. Front brake fluid reservoir (1);

2. Rear brake fluid reservoir (2).
CAUTION
RISK OF BRAKE FLUID SPILLS. DO NOT PULL THE
BRAKE LEVER WHEN THE COVER FIXING SCREWS ARE
LOOSE OR, MAINLY, WHEN THE BRAKE FLUID RESER-
VOIR COVER HAS BEEN REMOVED.
• Undo and remove the two screws fixing the brake fluid reservoir cover.
CAUTION
AVOID PROLONGED AIR EXPOSURE OF THE BRAKE FLUID. BRAKE FLUID IS HYGROSCOPIC
AND ABSORBS MOISTURE WHEN IN CONTACT WITH AIR. LEAVE THE BRAKE FLUID RESER-
VOIR OPEN ONLY FOR THE TIME NEEDED TO COMPLETE THE TOPPING UP PROCEDURE.
• Depending on whether you are work-
ing on the front (1) or the rear (2) brake
reservoir, lift and remove the relevant
cover (3 or 5) and gasket (4 or 6).
TO AVOID SPILLING FLUID WHILE TOPPING-UP, KEEP

THE TANK PARALLEL TO THE RESERVOIR EDGE (IN
HORIZONTAL POSITION).
DO NOT ADD ADDITIVES OR OTHER SUBSTANCES TO

THE FLUID.
WHEN USING A FUNNEL OR ANY OTHER ELEMENT,

MAKE SURE IT IS PERFECTLY CLEAN.
MAIN - 30
• Top-up the reservoir you are working with (1 or 2) until the level goes over the minimum
marked MIN.
CAUTION
TOP-UP TO MAXIMUM LEVEL MARK ONLY WHEN BRAKE PADS ARE NEW. BRAKE FLUID LEV-
EL DECREASES GRADUALLY AS BRAKE PADS WEAR OUT.
WHEN TOPPING-UP, DO NOT EXCEED THE MAXIMUM LEVEL MARK WHEN BRAKE PADS ARE
WORN AS YOU RISK SPILLING FLUID WHEN CHANGING THE BRAKE PADS.
• Check braking efficiency.
• In case of excessive travel of the brake lever or poor performance of the braking system,
purge the air in the system.
Clutch system
Adjusting the lever
Adjustment clutch when the engine stops or the

vehicle tends to move forward even when clutch
lever is operated and the gear engaged, or if the
clutch "slides", resulting in acceleration delay con-
sidering the engine revs.
Minor adjustments can be carried out through the
set screw (1) ):
• Remove the protection casing (2).

• Loosen the nut (3) (screw in).
• Turn the set screw (1) until the empty
travel at the clutch lever end is approx-
imately 10 - 15 mm (0.39 - 0.59 in) (see
figure).
MAIN - 31
• Tighten (unscrew) the nut (3), locking

the set screw (1).
• Check the empty travel at the clutch
lever end.
• Refit he protection casing (2).
• If the set screw (1) is fully screwed, fully
unscrewed or it is not possible to obtain
the correct empty travel:
• Remove the protection casing (2).
• Screw the nut (3) fully on the set screw
(1).
• Screw the set screw (1) completely.
• With a plain slot screwdriver (or a coin)
unscrew and remove the cap (4).
• Insert the special spanner (5) supplied

with the toolkit, and loosen the internal
nut (6).
• Introduce a plain slot screwdriver into
the special spanner (5) and tighten the
set screw (7) completely.
• Loosen the set screw (7) half a turn,
about 3 - 4 mm (0.12 - 0.16 in), of the
lever travel (8).
• Tighten the set screw (7) with the
screwdriver, operate the special span-
ner (5) and tighten the internal nut (6).
• Screw the cap (4) again.
• Check the empty travel at the end of
the clutch control lever (10 - 15 mm,
0.39 - 0.59 in ).
• Refit the left side fairing .
• Start the engine.
• Operate the clutch fully and engage the
first gear.
Make sure that the engine does not stop, that the
vehicle does not tend to move forward and that the
clutch does not "slip" when accelerating or riding.
WARNING
MAIN - 32
CHECK THE CLUTCH CONTROL CABLE IS IN GOOD CON-

DITIONS: THERE SHOULD BE NO SIGNS OF CRUSHING
OR WEAR ALL ALONG THE SHEATH.
• Lubricate the clutch wire frequently with an appropriate grease to avoid early wear and cor-
rosion.
See also
Side fairings
Headlight adjustment
NOTE
IN COMPLIANCE WITH LOCAL LEGAL REQUIREMENTS, SPECIFIC PROCEDURES MUST BE
FOLLOWED WHEN CHECKING LIGHT BEAM ADJUSTMENT.
For a quick check of the correct adjustment of the
front light beam:
• Place the vehicle 10 m (32.81 ft) away

from a vertical wall and make sure the
ground is level.
• Turn on the low-beam light, sit on the
vehicle and check that the light beam
projected to the wall is a little below the
headlight horizontal straight line (about
9/10 of the total height).
To adjust the light beam:
• Operating on both sides, undo the

screw.
• Adjust the headlamp until the desired
position is obtained.
• Working from both sides, tighten the
screw. After adjusting:
NOTE
CHECK THAT THE LIGHT BEAM VERTICAL DIRECTION IS
CORRECT.
MAIN - 33
INDEX OF TOPICS
TROUBLESHOOTING TROUBL
RX SX 125 Troubleshooting
CAUTION
IF THERE IS ANY ENGINE FAILURE, THE CONTROL UNIT
DOES NOT TURN ON THE EFI WARNING LIGHT.
THE EFI WARNING LIGHT IS INACTIVE IN THIS VEHICLE.
THE OPERATOR WHO ENCOUNTERS A FAILURE IN THE
ENGINE MUST CARRY OUT ALL THE PRESCRIBED AX-
ONE CHECKS WITH THE AIM OF ENSURING THE ENGINE
HAS BEEN THOROUGHLY CHECKED.
TROUBL - 35
INDEX OF TOPICS
ELECTRICAL SYSTEM ELE SYS

RX SX 125 Electrical system
Components arrangement
ELE SYS - 37
Electrical system RX SX 125
Components - Key (RX/SX 125):
1. Front headlamp
2. Coil
3. fuses
4. Battery
5. Turn indicators
6. Voltage regulator
ELE SYS - 38
7. Rear light
8. Right rear turn indicator
9. Speed sensor
10.STARTER MOTOR
11.Neutral sensor
12.Pick-up sensor
13.Intake air valve (MAJ2)
14.Spark plug
15.Left front turn indicator
16.Mixer oil level sensor
17.CDI control unit
18.Coolant temperature thermistor
19.Instrument panel
20.Front right turn indicator
21.Air temperature sensor
22.RAVE (Full Power) control solenoid
23.Horn
24.Throttle valve position sensor
25.Rear right turn indicator
Electrical system installation

INTRODUCTION
Scope and applicability
The purpose of this document is to define cables laying, their fastening on the motorcycle and possible
criticalities, special checks on connections and layouts, all this with the aim of obtaining vehicle relia-
bility.
Materials used and corresponding quantities
The electrical system consists of the following cable harnesses and parts:
• 1 Main Cable Harness
• 1 Front Tail Light Cable Harness
• 1 Ground lead
• 1 Cap for Magura Switches
• 1 Safety Diode
• 10 178x4 Large black clamps
• 3 98x2.5 Small black clamps
• 3 Rubber clamps
Special checks for the correct connection and laying of cables
This is the list of connectors the operator in charge of fitting must check they are correctly connected:
ELE SYS - 39
• Instrument panel connector

• Pick Up connector
• Regulator connector
• Control unit connectors
• Ground eyelets
• Key switch connector
• Left Light Switch Connector
The connectors listed (indicated with a green dot on the photo) are considered the most critical of all
because a possible disconnection may cause the motorcycle to stop. Undoubtedly the connection of
the rest of connectors is also important and essential for the correct operation of the vehicle.
Vehicle sections
The wiring distribution is subdivided in three essential sections, as indicated in the figure.
1. Front section
2. Central section
3. Rear section
Front side
TABLE A - MAIN CABLE HARNESS AND DI-

ODE POSITION
1. Diode
2. Clamp
3. Clamp
ELE SYS - 40
TABLE B - ENGINE AND CARBURETTOR

4. Faston Horn
5. Horn
TABLE C - FRONT
6. Metallic clamp
7. Left light switch connector
TABLE D - FRONT
8. Instrument panel connector
9. Key switch connector
10. Front left arrow connector
11. Front right arrow connector
12. Front tail light connector
13. Front headlight connector
14. Clamp
15. Clamp
TABLE E - FRONT
16. Clamp
17. Rubber cap
ELE SYS - 41
TABLE F - FRONT
• Headlight cable harness

• Place the cable harness in the front inner part.
ELE SYS - 42
Central part
TABLE A - MAIN CABLE HARNESS LAYING
• Metallic clamp
TABLE B - FILTER CASING AND CONTROL

UNIT
1. Air temperature sensor connector
2. Clamp
3. Regulator connector
TABLE B - FILTER CASING AND CONTROL

UNIT
4. Cable harness to the bolt
5. Fuses position
6. Turn indicators connector
7. Clamps
TABLE D - FILTER CASING AND CONTROL

UNIT
8. Air solenoid connector
9. Generator connector
10. Pick-up earth connector
11. Cable harness laying
12. Clamp
ELE SYS - 43
TABLE E - FILTER CASING AND CONTROL

UNIT
13. ECU 1 connector
14. ECU 2 connector
15. Oil reserve connector
16. Diagnosis connector
TABLE F - ENGINE AND CARBURETTOR
• Heater connector
TABLE G - ENGINE AND CARBURETTOR
• Throttle valve sensor connector
TABLE H - ENGINE AND CARBURETTOR

17. Clamps
18. Clamp
19. Speed sensor connector
20. Pick-up connector
21. Neutral sensor connector
22. Stop switch connector
ELE SYS - 44
TABLE I - SADDLE PILLAR

24. Ground eyelets
25. Clamps
TABLE J - GROUND LEAD FITTING

26. Ground eyelets
27. Faston coil
28. Ground lead
29. Coil
ELE SYS - 45
Back side
TABLE A - SADDLE PILLAR

1. Rear left arrow connector
2. Rear headlight connector
3. License plate connector
4. Rear right arrow connector
5. Clamp
TABLE B - LICENSE PLATE HOLDER PRE-FITTING

7. License plate light cable harness
8. Rear left arrow cable harness
9. Rear light cable harness
10. Rear left arrow cable harness
ELE SYS - 46
TABLE C - LICENSE PLATE HOLDER PRE-FITTING
ELE SYS - 47
TABLE D - SPEED SENSOR

12. Cable harness passes together with brake pipe
13. Cable harness passes together with brake pipe
14. Clamp
ELE SYS - 48
General wiring diagram
Components key :
1. MULTIPLE CONNECTORS
2. ECU DIAGNOSIS
3. AIR TEMPERATURE SENSOR
4. ELECTRONIC INSTRUMENT PANEL
ELE SYS - 49
5. LOW OIL SENSOR

6. TURN INDICATORS
7. LEFT LIGHT SWITCH
8. KEY SWITCH
9. HORN
10.REAR LEFT TURN INDICATOR
11.REAR LIGHT
12.LICENSE PLATE LIGHT
13.REAR RIGHT TURN INDICATOR
14.FUSES
15.FRONT STOP SWITCH
16.REAR STOP SWITCH
17.BATTERY
18.FUEL HEATER
19.NEUTRAL POSITION SENSOR
20.SPARK PLUG
21.IGNITION COIL
22.REGULATOR
23.GENERATOR
24.PICK-UP
25.AIR SOLENOID
26.THROTTLE SENSOR (TPS)
27.SPEED SENSOR
28.CDI CONTROL UNIT
29.RIGHT FRONT TURN INDICATOR
30.FRONT HEADLAMP
31.FRONT LEFT TURN INDICATOR
32.DIODE
33.RAVE SOLENOID (OPTIONAL)
Cable colours - key:
Ar orange
Az sky blue
B blue
Bi white
G yellow
Gr grey
M brown
N black
ELE SYS - 50
R red
Ro pink
V green
Vi purple
CDI Control unit pinout:
1. RAVE VALVE
2. K LINE
3. + LIVE
4. TEMPERATURE SENSOR
5. +5V TPS
6. MIL BULB
7. MAJ2 VALVE
8. SPEED OUT
9. PICK-UP IN
10.RPM OUT
11.KILL IN
12.GND
13.TPS IN
14.COIL
1. + SPEED SENSOR
2. - SPEED SENSOR
3. GND SIGNALS
Instrument panel pinout:
1. LEFT INDICATORS INPUT

2. RIGHT INDICATORS INPUT
3. NEUTRAL INPUT
4. INPUT FOR HIGH-BEAM LIGHTS
5. SPEED SENSOR INPUT
6. -
7. OIL LEVEL SENSOR
8. -
9. -
10.-
11.+ LIVE
12.RPM INPUT
13.GENERAL GROUND
14.+ BATTERY
ELE SYS - 51
15.-
16.-
17.-
18.EFI WARNING LIGHT
Checks and inspections
Dashboard
To change the setting from km/h to Mph or vice

versa:
• hold down the MODE button when in-

serting the key until WS is displayed in
the lower right hand side angle (when
the MODE button is released, the word
END is displayed).
• Pressing the MODE switch fast, the

km/h and Mph words are displayed.
• Hold down the MODE button (until dashes - - - - are displayed and the current setting is
displayed (km/h or Mph).
• Pressing the MODE switch fast, you can shift from km/h to Mph.
• After selecting the desired unit of measurement, press the MODE button for >3 seconds to
set it.
ELE SYS - 52
• To exit, turn the key to OFF.
CONFIGURATION OF WHEEL SIZE ON IN-

STRUMENT PANEL
The first time the RX125 - SX125 instrument panel
is switched on, it must be configured according to
the correct wheel size.
Upon switching on, the instrument panel is as
shown in the figure.
Briefly press the MODE button in the instrument

panel and the screen corresponding to the 1891
mm (74.45 in) size for the SX125 model is dis-
played.
Briefly press the MODE button in the instrument

panel and the screen corresponding to the 2066
mm (81.34 in) size for the RX125 is displayed.
In order to configure the instrument panel, press the MODE button until the letters WS are shown on
the LCD on the right-hand bottom side.
Now remove and insert the key again. The instrument panel will first turn on the warning lights and the
active segments on the LCD. Afterwards, it will display the pre-set wheel size value and then it will shift
to regular operation.
Recovery procedure
If an incorrect wheel size value has been configured, the instrument panel can be brought back to the
correct configuration.
The procedure is as follows:
• remove the key
ELE SYS - 53
• press the MODE button and insert the key again

• press and hold the MODE button until the letters WS are shown on the LCD on the right-
hand bottom side (5 sec)
• always holding down the MODE button, operate the high-beam lights to flash 5 times
• release the MODE button and 0001 or 0002 is displayed
• press the MODE button again to change from 0001 (SX 125 17 wheel) to 0002 (RX 125 18
wheel) and vice versa. Hold down the MODE button to confirm and WS will be displayed
• release the MODE button, then set the key to OFF
Resetting the odometer

The odometer can be reset only once and within 200 km (124.27 mi)
• remove the key

• press the MODE button and insert the key again
• press and hold the MODE button until the letters WS are shown on the LCD on the right-
hand bottom side (5 sec)
• always holding down the MODE button, operate the high-beam lights to flash 10 times +
turn indicators to flash 5 times
Service warning light reset
The service warning light is reset as follows :
• hold down the MODE button when in-

serting the key until WS is displayed in
the lower right hand side angle (when
the MODE button is released, the word
END is displayed).
ELE SYS - 54
• Press the MODE switch fast until the

service icon (Wrench symbol) is dis-
played. The words km/h - Mph and OIL
word are displayed first.
• Hold down the MODE button until the

dashes ---- are displayed. Once the
key is released, the words NO CLEAR
will be displayed.
• Pressing the MODE switch fast, you

can shift from NO to YES and vice ver-
sa.
• If YES CLEAR is displayed, press the
MODE switch and hold it for more than
three seconds to reset the service icon
(Wrench symbol).
• To exit turn the key to OFF.
CAUTION
IF A SCREEN DIFFERENT FROM THOSE DESCRIBED IS
DISPLAYED, EXIT BY TURNING THE KEY TO OFF.
ELE SYS - 55
Ignition circuit
Key:
1. Instrument panel
2. Key switch
3. Battery
4. fuses
5. CDI control unit
ELE SYS - 56
Characteristic
Standard spark plug
NGK BR8ES
Standard spark plug (FULL POWER)
NGK R BR10ES
Electrode gap
0.7 - 0.8 mm (0.027 - 0.031 in)
Troubleshooting
• Check that the 7.5 A fuse and 20 A fuse are not damaged.
• Check the spark plug and replace it if necessary.
• Check the high voltage wire and the spark plug cap.
• Check the coil.
• Check the pick-up.
• Check that the 15 A fuses are in good conditions.

• Check the diode.
• Check the start-up relay.
• Replace the CDI by another one in proper operating conditions.
Battery recharge circuit
System diagram key:
ELE SYS - 57
1. Instrument panel
2. Key switch
3. fuses
4. Battery
5. Voltage regulator
6. Generator
Recharge check
• Start the engine and make it run at 6000 rpm.

• Connect a tester in voltmeter function to check the direct current on the battery leads.
• Turn on the low-beam lights.
• The voltage must be between 13.5 and 15 V.
Troubleshooting
• Check that the fuses are in good conditions.

• Check the starter button.
• Check the start-up relay.
• Check the starter motor.
Control data
Flywheel check
• Disconnect the alternator cable con-

nector.
• Start the engine and make it run at
5000 rpm.
• With the pocket tester measure the
voltage (alternating current) among the
three yellow cables. If the value indica-
ted by the tester is below 53 V, the
generator is faulty.
Standard off-load voltage: above 53 V (AC) at

6000 rpm.
ELE SYS - 58
Voltage regulator check
• Output voltage 13.5 V - 15 V

• Output current higher than 10 A (with
load)
Turn signals system check
Turn indicator device check

Check placing the tester probes on the poles:
+ / - 5.8 kOhm.
- / L (bulb) 5.3 kOhm.
- / L (bulb) 4.8 kOhm.
• Undo and remove the screw and re-

move the protection glass with caution
so as not to break the fitting tooth.
• Slightly press the bulb and turn it anti-
clockwise.Take out the bulb from its
fitting.
• Upon replacement, insert a bulb of
equal rating in the bulb holder, making
the two guiding pins coincide with their
guides on the bulb holder.
ELE SYS - 59
Horn control
Testing voltage: 13 V (nominal 12 V)

Input: < 3.5 A
With a tester in ohmmeter function check the con-

tinuity of the contacts as per the diagram below.
Diode check
• Disconnect the two-way connector

(white).
To check diodes operation:

CAUTION
UPON REFITTING, MAKE SURE THE ELECTRIC CONNEC-
TOR IS CORRECTLY COUPLED.
Test (C): the bulb does not turn on.

Test (D): the bulb turns on.
With a tester (in diode test function) check the val-

ues between the two male terminals inside the
diode as indicated in the figure.
Correct value (measurement A): 0 - 1 Ohm.
Correct value (measurement B):infinite.
If the tester cannot be used as a diode test tool,
supply 12 V voltage, interpose a 12 V - 2 W bulb
on the positive lead and connect the diode as in-
dicated in the figure.
CAUTION
DO NOT USE BULBS OVER 2 W BULB OR THE DIODE MAY
BE DAMAGED.
ELE SYS - 60
Lights list
Key:
1. Instrument panel
2. Horn
3. Diode
4. Left rear turn indicator
ELE SYS - 61
5. Rear light assembly

6. License plate light bulb
7. Right rear turn indicator
8. Front stop switch
9. Rear stop switch
10.fuses
11.Right front turn indicator
12.Front headlamp
13.Left front turn indicator
Troubleshooting:
• Check that the 15 and 20 A fuses are in good conditions.

• Check if the stop light bulb is in good conditions.
Switches:
With a tester check the continuity of the switches,
referring to the specific diagram provided.
If any malfunction is detected, replace the corre-
sponding switch unit.
FRONT AND REAR LIGHTS
ELE SYS - 62
BULBS
BULBS SX 125 RX 125
License plate bulb 5W 5W
Rear tail light /stop light led led
Front tail bulb 2V x 3W 2V x 3W
Front/rear turn indicator bulbs 4 x 10W 4 x 10W
Low-/high-beam light bulb HS1 HS1
Fuses
FUSE DISTRIBUTION
1. 20 A fuse From battery to ignition switch,

voltage regulator, clock.
2. 15 A Fuse From ignition switch to all light
loads and horn.
3. 7.5 A Fuse From ignition switch to ignition,
air solenoid, RAVE (Full Power) solenoid.
NOTE
THERE IS ONE SPARE FUSE.
Control unit
• The control unit has been designed for

internal self-diagnose. In case of mal-
function, install a control unit in proper
operating conditions on the vehicle.
ELE SYS - 63
Battery
BATTERY
(12 V - B9 - B)
(12 V - 4 A)
In case of malfunction check first that the recharge system works properly. To check the battery, remove
it from the vehicle, and proceed as follows; visually check that :
- there are no signs of sulphation (signalled by white colouring of one or more cells);
- the electrolyte level is between the two "MIN" and "MAX" reference notches;
- the container (outer casing) does not leak.
Charge the battery slowly for at least 10 hours. With a densimeter check the electrolyte density at every
cell after recharging. If the density is below 1.26 at any cell or if the off-load voltage is lower than 12V,
the battery surely needs to be replaced.
Speed sensor
Operating voltage: Vdc= 5÷24 V

Maximum voltage applicable: 26 V
Maximum reverse voltage: -16 V
Maximum power consumption: 10 mA
Operating temperature:
-20 °C ÷ +80 °C (-7.6 °F ÷ -112 °F)
ELE SYS - 64
Engine rpm sensor
Pick-up check
• Disconnect the connector of the pick-

up terminals.
• With a pocket tester (1000 Ohm scale)
measure the resistance between the
terminals of the yellow/blue and yellow/
white cables. The resistance value
measured should be between 190 and
300 Ohm.
• If the resistance is infinite or lower than
the set value, the pick-up needs to be
replaced.
Air temperature sensor
AIR TEMPERATURE SENSOR

5 °C (41 °F) 5310 Ohm
10 °C (50 °F) 4134 Ohm
25 °C (77 °F) 2053 Ohm
30 °C (86 °F) 1651 Ohm
40 °C (104 °F) 1090 Ohm
50 °C (122 °F) 738 Ohm
Ohm resistance (+/- 10%)
ELE SYS - 65
Air intake valve
Air valve resistance 70 - 80 OHM at 25 °C (77 °F)

Not powered: closed valve
Powered with 12V: open valve
Coil
Coil winding resistance

Primary 0.11 - 0.21 Ohm.
Secondary 4.3 - 8.1 kOhm
Checking
Use a pocket tester to check the coil. In every case
the continuity of the primary and secondary wind-
ings must be checked. The Ohm reading need not
be exact, but if the windings are not damaged, their
continuity must be detected according to the fol-
lowing Ohm resistance values described above.
ELE SYS - 66
Neutral sensor
Check the values with a tester:

- With the gear engaged, the tester indicates an
infinite resistance value.
- In neutral position, resistance is equal to 0 Ohm.
Connectors
ECU
CONNECTOR A
1 Pin 1 Speed sensor positive
2 Pin 2 Speed sensor signal
3 Pin 3 Signal ground connection
CONNECTOR B
1 Pin 1 Rave valve
2 Pin 2 "K" line
3 Pin 3 + live
4 Pin 4 Temperature sensor input
5 Pin 5 + 5V TPS
6 Pin 6 Mil bulb
7 Pin 7 Maj2 Valve
8 Pin 8 Speed output
9 Pin 9 Pick-up input
10 Pin 10 RPM output
11 Pin 11 Kill input
12 Pin 12 Ground connection
13 Pin 13 TPS input
14 Pin 14 HV coil
ELE SYS - 67
Dashboard
Instrument panel pinout:
1. LEFT INDICATORS INPUT

2. RIGHT INDICATORS INPUT
3. NEUTRAL INPUT
4. INPUT FOR HIGH-BEAM LIGHTS
5. SPEED SENSOR INPUT
6. -
7. OIL LEVEL SENSOR
8. -
9. -
10.-
11.+ LIVE
12.RPM INPUT
13.GENERAL GROUND
14.+ BATTERY
15.-
16.-
17.-
18.EFI WARNING LIGHT
ELE SYS - 68
INDEX OF TOPICS
ENGINE FROM VEHICLE ENG VE

Engine from vehicle RX SX 125
Vehicle preparation
CAUTION
BEFORE CARRYING OUT THE OPERATIONS BELOW, BEAR IN MIND THAT THE ENGINE MUST
BE REMOVED FROM THE CHASSIS TOWARDS THE BOTTOM; AFTERWARDS ARRANGE AND
POSITION THE NECESSARY TOOLS.
NOTE
GET A HOIST AND BELTS FOR LIFTING.
• Position the vehicle on its OPTIONAL front service stand.
• Support the vehicle rear part using a hoist, fastening two suitable belts to the rear frame.
• Remove the central and front side fairings.
• Remove the fuel tank.
• Lift the hoist arm until the belts are linked to the chassis and are taut.
• Remove the complete exhaust.
Removing the engine from the vehicle
• Remove the battery (1) from its hous-

ing.
• Before draining the cooling system,

prepare a container of suitable capaci-
ty.
• Empty the cooling system by undoing
the front screw set to "OUT" on the left-
hand side of the crankcase.
• Release the clamps and slide both
cooling system pipes off the engine.
ENG VE - 70
RX SX 125 Engine from vehicle
• Disconnect the oil pipes and cover them.
• Undo and remove the three screws

and remove the oil pump cover.
• Loosen the set nut.
• Slide off the throttle cable from the oil

pump.
CAUTION
UPON REFITTING, ADJUST THE THROTTLE CABLE TEN-
SION BY OPERATING THE NUT ON THE OIL PUMP.
ENG VE - 71
• Slide off the mixer oil pipe.

• Cover the tank outlet and pipe.
• Disconnect the spark plug tube.
• Disconnect the thermistor electric con-

nector.
• Loosen the locking washer completely

(2).
• Loosen the set screw (3) completely.
• Remove the clutch cable (4) from the
lever.
ENG VE - 72
• Unscrew and remove the gearbox oil

filler cap.
• With a small plain slot screwdriver, re-

move the clutch cable from its seat .
• Slide off the clutch cable.
CAUTION
UPON REFITTING CHECK THE CLUTCH LEVER CLEAR-
ANCE.
• Loosen the fixing screw and move the

oil hose guides.
• Detach the oil pipes from the engine
crankcase.
• Disconnect the engine oil breather pipe

from the crankcase.
ENG VE - 73
• Undo and remove the two screws fixing

the pinion protection cover and then
remove it.
CAUTION
TO FACILITATE SLIDING OFF THE TRANSMISSION PIN-
ION, SLIGHTLY LOOSEN THE DRIVE CHAIN.
• Remove the Seeger ring.
• Slide off the transmission pinion with the chain from the shaft.
• Disconnect the neutral gear sensor.
• Release the cables by removing the

clamps indicated.
ENG VE - 74
• Working from the left side of the vehi-

cle, undo the screw while keeping the
right-hand side nut tightened.
• Release the engine temperature sen-

sor.
ENG VE - 75
• Disconnect the connections.
• Remove the pipe from the hose guide.
• Remove the carburettor.
ENG VE - 76
• Remove the clamp and disconnect the

secondary air pipe.
• Undo and remove the screw discon-

necting the connectors of the system
ground connections.
• Undo and remove the screw and dis-

connect the speed sensor.
CAUTION
DUE TO THE ENGINE WEIGHT, THE FOLLOWING OPERATIONS REQUIRE THE INTERVENTION
OF A SECOND OPERATOR. FIRST AGREE ABOUT THE PROCEDURE TO BE FOLLOWED.
• Working from the right side and using
the suitable swingarm pin adjustment
tool, fully loosen the ring nut (5).
• Loosen the ring nut set bushing (6).
Specific tooling
ENG VE - 77
• Remove the front screw that fixes the

engine to the chassis and collect the
nut on the right-hand side of the vehi-
cle.
• Working from the right side and using

the suitable swingarm pin adjustment
tool, fully loosen the ring nut (5).
• Working from the left side, undo and

remove the swingarm pin and collect
the two washers.
• Remove the swingarm from the chas-
sis.
• Sliding it off from the left side of the vehicle, remove the engine from the chassis.
Installing the engine to the vehicle
• Move the engine with small alternating

movements until it is perfectly aligned
with the fixing holes.
• Insert the upper screw, fit the washer
and tighten the nut.
ENG VE - 78
• Insert the front screw that fixes the en-

gine to the chassis and fasten the nut.
• Place the swingarm on the chassis.

• Move it into position so that the holes
are aligned and, at the same time, in-
sert the pin fully from the left side.
• The correct adjustment of the swing-

arm pin clearance is obtained by prop-
erly seating the ring nut set bushing (1)
and screwing it another 1 / 4 of a turn.
CAUTION
GET THE ADEQUATE SWINGARM PIN ADJUSTMENT
TOOL.
Specific tooling
• Firmly hold the bushing (2) and tighten the ring nut (1) using a special tool.
• Now adjust the rear swingarm pin as follows:
- Using the adequate adjustment tool loosen the ring nut (1) completely working from the upper right
side.
- Tighten the ring nut set bushing (2) to the prescribed torque.
ENG VE - 79
- Tighten the ring nut (1) using an adequate special tool.

- Tighten the swingarm pin.
• Fit the speed sensor and tighten the

screw.
• Fit the carburettor.
• Replace the clamp and connect the

secondary air pipe.
• Place the rear brake pipe and the

speed sensor cable and tighten them
to the chassis fastening the cable
guide.
• Connect the following electric connectors in order:
ENG VE - 80
- System ground connections, tighten the screw.
- Connect the neutral gear sensor.
• Replace the clamps.
ENG VE - 81
- Control unit ground connection.
- Pick-up
- Generator.
• Connect the engine temperature sen-

sor connector.
ENG VE - 82
• Fit the transmission pinion with the

chain on the shaft.
• Fit the Seeger ring.
• Fit the pinion protection case and fix it

by means of two screws.
• Place the oil pipes on the engine crank-

case fastening them with the hose
guides.
ENG VE - 83
• Install the battery.

• Replace the clamp and connect the ex-
pansion tank pipe.
• Reposition the clutch cable in its seat.
• Tighten the gearbox oil filler cap.
• Fit the clutch cable (3) in the clutch lev-

er.
• Undo the set screw (4).
• Tighten the locking washer (5) partial-
ly.
• Check the clutch lever clearance.
ENG VE - 84
• Connect the thermistor electric con-

nector.
• Connect the spark plug tube.
• Place the throttle cable in the oil pump.
• Adjust the throttle cable tension by op-

erating the nut on the oil pump until it
is aligned with the two references.
ENG VE - 85
• Position the oil pump cover and tighten

the three screws .
• Place the cooling system pipes, re-

place the clamps.
• Make sure all engine fixing screws / locking nuts are tightened to the prescribed torque.
• Top-up coolant
• Check the drive chain tension and adjust if necessary.
NOTE
CARRY OUT AN OVERALL CHECK ON ALL THE COMPONENTS THAT HAVE UNDERGONE ANY
OPERATION, ESPECIALLY THAT:
- the electrical cables are correctly fastened with suitable clamps;
ENG VE - 86
CAUTION
AVOID TWISTING AND CRUSHING CABLES.
• the electrical connectors are correctly coupled;
• the pipes and unions are correctly fitted and secured with suitable clamps;
• the throttle and cold start cables slide freely and do not cause the handlebar to rotate.
ENG VE - 87
INDEX OF TOPICS
ENGINE ENG
RX SX 125 Engine
Gearbox
Gearbox shafts
Disassembling the gearbox
• Open the crankcase halves.

• Remove the gaskets from the crank-
case.
• Take out the countershaft.
• Fix the flywheel-side crankcase half on

the engine support with the adequate
screw and spacer.
• Take out both fork rod.
ENG - 89
Engine RX SX 125
• Unscrew and remove the desmodrom-

ic control fixing screw and collect the
washer.
• Slide off the three gear forks from the

guides of the desmodromic drum con-
trol.
• Remove the desmodromic drum con-

trol.
• Remove the O-ring.
ENG - 90
RX SX 125 Engine
• Rotate the crankcase half on the sup-

port to the standard position.
• Remove gearbox unit (primary + sec-
ondary).
Checking the primary shaft
• Check the state of the joints and

grooves. Max. admissible deviation (A)
0.03 mm (0.0012 in); Min. wear limit (B)
Diam. 24.96 mm (0.9827 in). Min. wear
limit (C) Diam. 20.96 mm (0.8260 in).
Min. wear limit (C) Diam. 16.97 mm
(0.6681 in).
Checking the secondary shaft
• Check the state of the joints and

grooves. Max. admissible deviation (A)
0.03 mm (0.0012 in); Min. wear limit (B)
Diam. 24.96 mm (0.9827 in). Min. wear
limit (C) Diam. 20.96 mm (0.8260 in).
Min. wear limit (C) Diam. 16.97 mm
(0.6681 in).
Checking the desmodromic drum
• Check the contact zone on fork (1) and the driving pin (2) of the forks for wear.
• Check the desmodromic drum grooves (3) for wear.
• Make sure that both ball bearings (4) rotate freely and check if there are signs of corrosion.
ENG - 91
Engine RX SX 125
• The lever roller (6) must rotate freely.

• Check that the stop tab (7) and the rel-
evant spring (8) work properly.
• Check that the gear shaft is not de-
formed. (A) Max. admissible deviation
= 0.15 mm (0.0059 in);
• Check that both fork shafts are not de-
formed. (B) Max. admissible deviation
= 0.05 mm (0.0020 in);
THE END OF THE FORK LONG SHAFT (9) THAT PRO-

TRUDES FROM THE CRANKCASE IS USED AS A TRANS-
MISSION STOP AND CAN BE BENT IN CASE OF EXCES-
SIVE LOAD (BUMPING).
THE DEVIATION CAN BE CHECKED BY REMOVING THE
CLUTCH COVER AND ROTATING THE LONG SHAFT.
Assembling the gearbox
• Place the guiding sleeve on the pri-

mary shaft to avoid damaging the oil
seal.
• Heat up the engine crankcase.
• Apply LOCTITE Anti-Seize on the
bearing seats present on the crank-
case.
• Fit the bearings in their seats.
• Fit the gear unit.
• Fit the 5th - 6th gear fork on the gear

pinion of the secondary shaft.
• Place the 2nd - 3rd gear fork and the
1st - 4th gear fork on the gear pinion of
the primary shaft. The 2nd - 3rd gear
fork must be installed with the printed
number 123 facing upwards. The 1st -
4th gear fork must be installed with the
printed number 113 facing upwards.
ENG - 92
RX SX 125 Engine
• Apply oil for gears on the grooves of

the desmodromic drum.
• Fit the desmodromic in the crankcase.
• Fit the washer and the desmodromic

control fixing screw and tighten them.
• Insert all the forks in the desmodromic

guides.
• Lubricate the gear shafts and insert
them in their seats, paying special at-
tention that the short gear shaft has its
chamfering side facing upwards and
that the seeger ring on the long one is
properly placed.
• Check that all the gear components
slide smoothly.
• Warm up the crankcase.

• Apply LOCTITE Anti-Seize to each
bearing seat of the countershaft.
• Fit the bearing.
• Fit the countershaft in the bearing.
ENG - 93
Engine RX SX 125
Starter motor
STARTER MOTOR
• Make sure that the toothing (1) is not

deformed or worn.
• Make sure that the O-ring (2) is not
damaged or worn.
• The electric starter motor is not fitted
for repair. If necessary, replace the
whole motor.
START-UP GEAR
• Make sure that the gears (3) are not

worn.
• The start-up gears must be blocked
with precision in one direction.
Removing the starter motor
• Undo and remove the two fixing screws.

• Remove the starter motor.
NOTE
THE STARTER MOTOR CAN ALSO BE REMOVED IF THE ENGINE IS FITTED TO THE VEHICLE.
Installing the starter motor
• Place the electric starter motor.

• Apply LOCTITE 221.
• Tighten the starter motor fixing screws.
ENG - 94
RX SX 125 Engine
Removing the idle gear
• Remove the magneto flywheel.

• Slide off the starter motor gear.
See also
Magneto flywheel removal
Fitting the idle gear
• Rotate the engine support so that it

faces upwards, flywheel side.
• Apply MOLYKOTE 111 to all the bear-
ing housings and the teeth of the start-
up gear unit.
• Install the start-up gear unit together
with the thrust washer in the hole with
the needle bearing.
Generator side
Removing the flywheel cover
• Lean the engine on the support in such

a way as to place the start-up cover
facing upwards.
• Undo and remove the six screws fixing
the flywheel cover.
ENG - 95
Engine RX SX 125
• Remove the flywheel cover.
Magneto flywheel removal
• Remove the flywheel cover.
• Remove the starter motor gear cover.
• Undo the two M5 screws and remove

the external "pick up".
ENG - 96
RX SX 125 Engine
• Place the extractor plate on the fly-

wheel and fix it with the three M6 Allen
screws. The flywheel cam must be fac-
ing the external "pick up", making sure
that the crankshaft is at TDC When
placing the extractor plate, make sure
that the position of the support pins is
correct.
• Undo and remove the M12x1 hexago-

nal screw and collect the locking wash-
er.
ENG - 97
Engine RX SX 125
• Fit the protection sleeve on the crank-

shaft thread.
• Insert the long threaded end of the ex-
tractor screw in the extractor plate and
remove the flywheel.
Removing the stator
• Undo and remove the three M6 stator

fixing screws.
• Remove the stator, the cable guide and

external locking.
• Remove the woodruff key from the
crankshaft.
Installing the flywheel
• Degrease the crankshaft conic part

and the flywheel.
• Place the flywheel matching the
grooves on the shaft.
• Place the washer and the magneto fly-
wheel fixing screw without tightening it.
• Place the flywheel up to the TDC
ENG - 98
RX SX 125 Engine
• Place the extractor plate correctly with

the locking bolts on the flywheel and fix
it with three screws (M6 x 16).
Specific tooling
AP0277455 Extractor plate to separate the
crankcase halves
• Tighten the magneto flywheel fixing

nut.
• Place the pick up, tighten the two pick-

up fixing screws and adjust the pick-up
distance to 0.55 mm (0.217 in).
ENG - 99
Engine RX SX 125
• Apply SILASTIC 732 RTV to the cable

guide of coil and stator, then slide it in
the crankcase hollow space.
• Fit the electric starter device cover on
the starter gear.
Stator installation
• Insert the woodruff key in the crank-

shaft.
• Place the stator.
• Tighten the three stator fixing screws.
Flywheel cover installation
• Apply a thin layer of SILASTIC 732

RTV on the flywheel cover centring.
• Place the flywheel cover.
ENG - 100
RX SX 125 Engine
• Tighten the six flywheel cover fixing

screws.
Clutch side
Removing the clutch cover
• Undo and remove the nine screws fix-

ing the clutch cover.
• Lift the clutch cover using two screw-

drivers as levers at the prearranged
points paying special attention not to
damage the seal surfaces and the gas-
ket.
• Remove the gasket.
ENG - 101
Engine RX SX 125
Disassembling the clutch
• Remove the pack of the clutch discs

from the clutch base.
• Remove the clutch base of the secon-

dary shaft.
Checking the clutch plates
• Undo and remove the six M5 fixing

screws (9) crosswise and remove the
clutch.
THE UPPER DISC IS USED AS A SPRING AND MUST BE

PUT BACK IN PLACE AT THE SAME UPPER POSITION.
• Check that the plain clutch discs (6) are not deformed; Max. distortion limit 0.15 mm (0.0059
in).
• Check that the coated clutch discs (5) are not worn; Max. wear limit, min. thickness 2.8 mm
(0.110 in).
THE UPPER DISC IS USED AS A SPRING AND MUST BE PUT BACK IN PLACE AT THE SAME
UPPER POSITION.
CHECK:
• Clutch bell (1) teeth sides and control gear (2) teeth sides.
ENG - 102
RX SX 125 Engine
• Cage and rollers of both needle bearings (3).

• Internal disc (4) toothing.
• Friction discs (5) for damage.
• Internal clutch discs (6) for damage, scores or wear
• The locking disc ball (7) must move freely and must not be worn.
• When refitting the clutch pay attention that the coated clutch disc placed at the upper end
must be fitted in the shortest slots (8).
• Screw the clutch fixing screws (9) without tightening, proceed to the tightening only after the
clutch has been fitted.
THE UPPER DISC IS USED AS A SPRING AND MUST BE PUT BACK IN PLACE AT THE SAME
UPPER POSITION.
Checking the clutch housing
• Check the worn guiding grooves of the

clutch bell (1); max. insertion depth (A)
= 0.5 mm (0.020 in).
ENG - 103
Engine RX SX 125
Checking the clutch hub
• When the clutch hub is worn it can cre-

ate problems with sliding of the hous-
ing. The hub should be replaced if the
surface of the spring has exceeded the
wear limits. Max. wear limit (A) 0.3 mm
(0.012 in).
Assembling the clutch
• Check that the needle bearings are in-

stalled on the secondary shaft.
• Install the clutch base.
• Fit the disc pack pre-assembled on the

clutch base which has been previously
placed on the secondary shaft.
Head and timing
ENG - 104
RX SX 125 Engine
Removing the head cover
• Undo and remove the four Allen

screws fixing the head cover.
• Remove the head cover.
• Remove both O-rings.
Removing the cylinder head
• Remove the head cover.

• Remove the five M8 Allen screws and
the locking washers.
• Remove the combustion chamber in-
sert together with the O-Ring.
See also
Removing the
head cover
Cylinder head
Checking the cylinder head
HEAD
• Clean off any combustion deposits in

the combustion chamber as well as
scales on the surfaces in contact with
the cooling water.
• Make sure the insert in the combustion
chamber is not damaged and the spark
plug thread is in good conditions.
• Make sure the seal surfaces are
smooth and not damaged.
ENG - 105
Engine RX SX 125
• The seal surface of the combustion

chamber insert gets slightly conic start-
ing from a 63 mm (2.48 in) diameter.
CYLINDER HEAD COVER
• Make sure the seal surfaces of the two

O-rings are clean.
• Make sure the cylinder head cover is
not damaged.
Cylinder-piston assembly
Removing the cylinder
• Remove the head.

• Working from both sides remove the
four fixing screws and collect the wash-
ers.
• Take out the cylinder with utmost care
trying not to damage the piston.
• Remove the gasket on the cylinder
base.
See also
Removing the
cylinder head
ENG - 106
RX SX 125 Engine
Disassembling the piston
• Remove the cylinder.

• Remove one of the two seeger rings of
the pin using a suitable tool.
CAUTION
BEFORE TAKING OUT THE PIN SEEGER RING, COVER
THE CRANKCASE OPENING WITH A CLOTH SO THAT THE
RING DOES NOT FALL INTO THE CRANKCASE.
NOTE
IT IS NOT NECESSARY TO REMOVE BOTH PIN SEEGER
RINGS.
• Tap the pin out with a suitable punch.

CAUTION
WHILE TAPPING OUT THE PIN, HOLD THE PISTON WITH
ONE HAND SO THAT THE CONNECTING ROAD DOES NOT
BEND.
• Remove the piston and collect the ball

retainer.
CAUTION
WHILE TAPPING OUT THE PIN, HOLD THE PISTON WITH
ONE HAND SO THAT THE CONNECTING ROAD DOES NOT
BEND.
See also
Removing the
cylinder
ENG - 107
Engine RX SX 125
Checking the cylinder
• Remove any scales formed by water in

the cooling interspace on the cylinder
(A).
• Clean off any combustion deposits
from the outlet port (B).
• Clean and check the groove of the O-
ring (C).
• Make sure all threads (D) are in proper
conditions.
• Make sure all the seal surfaces are
smooth and not damaged.
• Check the cylinder wall for wear.
Ovality: max. wear limit 0.02 mm (0.0008 in).
Checking the piston
• Check if there are marks of pinging/head knocking on the "squish" area and the piston cen-
tre.
• Make sure the piston is not damaged or shows signs of pressure or galling.
SLIGHT SCORINGS CAN BE ELIMINATED BY RUBBING THEM WITH EMERY CLOTH (GRAIN 600
- 800).
• Clean the piston crown and the bottom side as well as the piston ring grooves.
CLEAN THE RING GROOVES THOROUGHLY WITH A SCRAPER OR PREFERABLY WITH A

PIECE OF AN OLD PISTON RING.
• Clearance between piston and wall = Cylinder diam. - Piston diam.; Nominal clearance 0.020
- 0.035 mm (0.00079 - 0.00138 in); Max. wear limit 0.080 mm (0.00315 in).
IF THIS WEAR LIMIT IS EXCEEDED, USE AN OVERSIZED PISTON OR REPLACE BOTH THE
CYLINDER AND THE PISTON.
WHEN THE PISTON IS REPLACED, ALSO REPLACE THE TWO SEEGER RINGS (1), THE PIN (2)
AND THE BALL RETAINER (3).
ENG - 108
RX SX 125 Engine
• The pin (2) should adjusted to the pis-

ton without considerable clearance.
• Make sure the grooves of the seeger
rings (4) are not worn.
• Measure the axial clearance of the

rings with a thickness gauge; max.
wear limit = 0.10 mm (0.0039 in).
• Distance between the ends of the pis-
ton ring. Nominal distance between the
ends 0,05 - 0,20 mm (0.0019 - 0.0079
in) Max. wear limit 0.8 mm (0.032 in).
TO MEASURE THE DISTANCE BETWEEN THE ENDS OF A

PISTON RING, PLACE THE RING IN THE CYLINDER USING
THE PISTON AS A PUSHING TOOL AND CHECK THE DIS-
TANCE WITH A THICKNESS GAUGE.
Fitting the piston
• Position the cylinder base gasket.
THE CRANKCASE GASKET SHOULD NOT PROTRUDE OR RECESSED COMPARED WITH THE
CYLINDER BASE SURFACE SO AS TO AVOID COOLANT LEAKING INTO THE CRANKCASE.
• Place a seeger ring in the piston groove.
USE NEW SEEGER RINGS ONLY. MAKE SURE THE OPEN ENDS OF THE RINGS ARE FACING
DOWNWARDS.
ENG - 109
Engine RX SX 125
• Apply engine oil on the lubrication

ducts for the main bearings of the
crankshaft, on the head bearings and
on the rod small ends.
• Make the ball retainer slide on the con-
necting rod.
• Place the piston on the connecting rod

and insert the pin correctly in its posi-
tion.
FOR SAFETY REASONS COVER THE CRANKCASE WITH

A CLEAN CLOTH SO THAT THE SEEGER RINGS DO NOT
FALL INTO THE CRANKCASE.
• Place the second seeger ring.
FOR SAFETY REASONS COVER THE CRANKCASE WITH

A CLEAN CLOTH SO THAT THE SEEGER RINGS DO NOT
FALL INTO THE CRANKCASE.
Installing the cylinder
• Use the wrench for piston rings.
MAKE SURE THE PISTON RINGS ARE FITTED WITH THEIR ENDS BESIDE THE FIXING PIN IN
THE GROOVE. APPLY OIL FOR TWO-STROKE ENGINES TO THE CYLINDER WALL.
Specific tooling
AP0876973 Piston ring clamp 54 mm
ENG - 110
RX SX 125 Engine
• Place the cylinder.
ONLY ASSEMBLE TOGETHER PISTONS AND CYLINDERS

BELONGING TO THE SAME TOLERANCE RANGES.
• Take out the wrench for piston rings.

• Working from both sides, fasten the
cylinder crosswise with the four M8
nuts and relevant washers.
TIGHTEN THE FIXING NUTS AGAIN, WHEN THE ENGINE

IS COLD, AFTER THE FIRST 500 KM (310 MI).
Selecting the cylinder

• The cylinder size code is stamped on
the surface of the cylinder base.
• Read the cylinder diameter at TDC.
• The bottom section of the cylinder sur-
face undergoes only slight wear. If the
cylinder TDC area is very worn (it is no
longer bright, rough and sharp), it can
be inferred that the engine has been
working fed on a fuel with too much
sulphur.
Cylinder "A" Diam. 54.000 - 54.010 mm (2.12597

- 2.12637 in) Diam. 54.060 mm (2.12834 in)
Cylinder "AB" Diam. 54.010 - 54.015 mm (2.12637
- 2.12657 in) Diam. 54.065 mm (2.12853 in)
Cylinder "B" Diam. 54.015 - 54.025 mm (2.12657
- 2.12696 in) Diam. 54.075 mm (2.12893 in)
Selecting the piston

Measure the piston diameter with a micrometer, 11.5 mm from the piston bottom edge.
ENG - 111
Engine RX SX 125
The piston nominal size is stamped on the piston crown.

Pistons are grouped in types according to their sizes:
• PISTON "A"; Piston diam. = 53.98 mm (2.1252 in), wear limit = 53.93 (2.1232 in), matching
cylinder: "A" or "AB".
• PISTON "B"; Piston diam. = 53.99 mm (2.1256 in), wear limit = 53.93 (2.1236 in), matching
cylinder: "B" or "AB".
• PISTON "Oversize 1"; Piston diam. = 54.00 mm (2.1260 in), wear limit = 53.93 (2.1240 in),
matching cylinder: "B" or re-smoothed cylinder.
• PISTON "Oversize 2"; Piston diam. = 54.00 mm (2.1264 in), wear limit = 53.93 (2.1244 in),
matching cylinder: re-smoothed cylinder.
Pistons are available with different types of piston rings which are identified with their part number:
• PISTON (code 294583); chrome-plated PISTON RING (code 215670)

• PISTON (code 294587); chromium-ceramic PISTON RING (code 215720)
• PISTON (code 294589); chromium-ceramic PISTON RING (code 215820)
• PISTON (code 294588); chromium-ceramic PISTON RING (new type) (code 215825)
IF A PISTON SHOWS SIGNS OF EXCESSIVE WEAR AS IT HAS BEEN FUNCTIONING WITH LOW
QUALITY FUEL (HIGH IN SULPHUR), USE CHROMIUM-CERAMIC RINGS AND CHANGE THE
FUEL BRAND USED.
Installing the cylinder head
• Fit the O-ring in the cylinder groove.
• Place the head.

• Tighten in a star sequence the five
socket head screws fixing the head, to-
gether with the washers.
TIGHTEN THE FIXING NUTS AGAIN, WHEN THE ENGINE

IS COLD, AFTER THE FIRST 500 KM (310 MI).
ENG - 112
RX SX 125 Engine
Installing the head cover
• Fit the O-rings.
• Fit the head cover already fitted with

the thermostat.
• Tighten crosswise the four screws fix-
ing the head cover.
Crankcase - crankshaft
Splitting the crankcase halves
• Remove the snap ring of the crankshaft

and that of the countershaft.
ENG - 113
Engine RX SX 125
• Remove the control gear from the

crankshaft.
• Remove the two countershaft gears

with a suitable tool.
• Remove the gear shaft and collect the

thrust washer.
ENG - 114
RX SX 125 Engine
• Undo and remove the screw fixing the

lever.
• Remove the lever and collect the

spring, the spacer and the washer.
• Undo and remove the nine screws fix-

ing the crankcase halves.
• Undo and remove the support screw.
ENG - 115
Engine RX SX 125
• Place the extractor plate.

• Fit the three fixing screws.
• Adequately centre the plate with refer-
ence to the crankshaft.
• Tighten the three fixing screws.
• Screw the long threaded end of the ex-
tractor screw on the extractor plate un-
til the crankcase half on the clutch side
starts to get detached. Facilitate the
detachment of the crankcase by tap-
ping the secondary shaft with a rubber
mallet, being careful that the crank-
case half gets detached evenly. Be ex-
tremely careful not to tap the seal
surfaces.
• Check the thrust washer of the main
shaft. When detaching the crankcase,
the washer may get glued inside the
crankcase halves.
• Once the crankcase halves have been
detached, remove the extracting tool
before the crankcase halves are fully
apart.
Specific tooling
crankcase halves
Removing the crankshaft
• Turn the crankcase halves on the sup-

port so that the high ignition is facing
upwards.
ENG - 116
RX SX 125 Engine
• Place the extractor plate and fix it with

four M6 fixing screws, but do not fully
tighten them.
• Adequately centre the tool.
• Tighten the four M6 fixing screws.
• Insert the extractor screw with the long
threaded end in the extractor plate.
Specific tooling
crankcase halves
• Thrust out the crankshaft operating on
the extractor plate screw.
ACT WITH CAUTION WHEN EXTRACTING THE CRANK-

SHAFT AS IT IS HEAVY.
SUPPORT IT ADEQUATELY SO AS TO AVOID DAMAGES.
Inspecting the crankcase halves
• Clean the crankcase halves, the ball bearings and all the bearing gaskets with a non-ag-
gressive detergent.
DO NOT USE DEGREASERS OR SOLVENTS.

• Clean all the seal surfaces.
BE CAREFUL NOT TO DAMAGE THE SEAL SURFACES WHEN CLEANING THEM.

• Check that the crankcase halves show no signs of cracks or any kind of damage.
• Check that the oil flow in the main bearings is not obstructed; clear the passage with com-
pressed air if required.
• Check that the pin of the contact screw moves smoothly and that the spring is pre-loaded.
The round end of the pin should not be worn. Fix the contact screw with SILASTIC 732 RTV.
• When the water delivery intake is replaced, fix it with LOCTITE 648.
• Make sure that the oil seals are not worn or damaged.
ENG - 117
Engine RX SX 125
• Check that all ball bearings move smoothly and are not worn. When replacing the ball bear-
ings, check the negative allowance in the crankcase. Min. ALLOWANCE = 0.010 mm
(0.00039 in).
ONLY THE BALL BEARING SEATS OF THE DESMODROMIC DRUM ARE SLIDING.
• Make sure that all the seal surfaces are proper conditions and not damaged.
• Check that all threads are in proper conditions.
FLYWHEEL SIDE CRANKCASE HALF
• Pre-warm the crankcase half at ap-

prox. 60 - 100 °C (140 - 212 °F).
• Remove both reference pins (1).
PLACE THE CRANKCASE HALF ON A SUITABLE LEVEL

SURFACE TO AVOID DAMAGING THE SEAL SURFACES.
FLYWHEEL SIDE CRANKCASE HALF
• Take out the oil seal (2) and the ball

bearing (3) of the crankshaft with a suit-
able punch (4).
BEHIND THE BALL BEARING THERE ARE SOME SHIM

WASHERS FOR THE AXIAL CLEARANCE OF THE CRANK-
SHAFT (5).
ALSO REPLACE THE OIL SEAL IF THE BALL BEARING IS
REPLACED.
• Fit the oil seal of the crankshaft using

a punch (6).
THE BALL BEARING OF THE CRANKSHAFT (3) IS FITTED

TOGETHER WITH THE CRANKSHAFT AFTER CHECKING
THE AXIAL CLEARANCE.
Specific tooling
• First remove the oil seal (8) and then take out the ball bearing (7) of the main shaft with a
suitable punch.
DO NOT DAMAGE THE OIL SEAL HOUSING WHEN REMOVING THE SEAL.
ENG - 118
RX SX 125 Engine
• Insert the oil seal (8) of the main shaft from the inside to the outside using a punch for fitting.
Specific tooling
• Push the ball bearing (7) of the main shaft using a suitable punch.
THE CLOSED SIDE OF THE BALL RETAINER SHOULD BE FACING THE OIL SEAL.
• The ball bearings of the secondary shaft (9) and those of the countershaft (10) can be taken
out using the specific extractor for bearings.
PLACE THE OLD CRANKCASE HALF GASKET UNDER THE EXTRACTOR PLATE TO AVOID
DAMAGING THE SEAL SURFACE.
Specific tooling
AP0277455 Extractor plate to separate the crankcase halves
• The ball bearings of the secondary shaft and those of the countershaft can be taken out
using the specific extractor for bearings.
THE REAR SIDE OF THE BALL BEARING RETAINER SHOULD BE FACING OUTWARDS.
• The needle bearing for the gears of the starter motor can be pulled using a specific extractor
for bearings.
CLUTCH SIDE CRANKCASE HALF
• Pre-warm the crankcase half at 60 - 100 °C (140 - 212 °F).

• Remove both reference pins (11) for the clutch cover.
PLACE THE CRANKCASE HALF ON A SUITABLE LEVEL SURFACE TO AVOID DAMAGING THE
SEAL SURFACES.
• Take out the oil seal (12) of the crank-
shaft.
• Take out the ball bearing (13) of the
crankshaft using a suitable punch. Re-
fit following the same procedure, with
the closed side of the bearing retainer
facing inwards.
ENG - 119
Engine RX SX 125
• In order to refit the oil seal (12) of the

crankshaft, push it into position from
the outside to the inside with a punch
for fitting (14).
THE OIL SEAL EDGE SHOULD BE FACING OUTWARDS.

THE OIL SEAL SHOULD NOT BE CONTACTING THE BALL
BEARING.
Specific tooling
• Remove the ball bearing (15) of the
secondary shaft and that of the main
shaft with a suitable punch. Refit fol-
lowing the same procedure.
THE CLOSED SIDE OF THE RETAINER OF THE BEARING

ON THE SECONDARY SHAFT (15) SHOULD BE FACING
OUTWARDS WHEREAS IT SHOULD BE FACING INWARDS
FOR THE BEARING ON THE MAIN SHAFT (16).
• Remove the M5 countersunk screw

(17) and the locking washer and take
out the ball bearing (19) of the coun-
tershaft. Follow the same procedure to
refit the bearing, fixing the M5 counter-
sunk screw with LOCTITE 221.
THE CLOSED SIDE OF THE BALL BEARING RETAINER

SHOULD BE FACING OUTWARDS.
• Push both reference pins (11) in their positions on the clutch cover.
ENG - 120
RX SX 125 Engine
Checking the counter shaft
• Check countershaft for wear: (1) Fly-

wheel side bearing seat, Minimum
wear limit diameter: 14.94 mm (0.5882
in) ; (2) Clutch side bearing seat, Mini-
mum wear limit diameter: 24.94 mm
(0.9819 in) ;
• Make sure the groove of the snap ring
(3) is not worn or damaged.
• Check the internal (4) and external

toothing (5) of the gears controlling the
countershaft for wear.
THE GEARS AND THE O-RINGS ON THE REAR SIDE OF

THE COUNTERSHAFT GEAR ON THE CRANKSHAFT
MUST BE REPLACED AFTER 15,000 KM.
Installing the crankshaft
UPON REFITTING, ALWAYS REPLACE THE GASKETS, THE SAFETY CIRCLIPS, THE O-RINGS
AND THE OIL SEALS REMOVED.
• Pre-warm the crankcase at 90 - 100 °
C (194 - 212 °F)
• Fix the flywheel side crankcase half to
the support and tighten the screw and
the spacer.
• If necessary, fit the shim washers nee-
ded to the flywheel side crankcase half.
• Apply LOCTITE Anti-Seize on the
bearing seats on the crankshaft.
• Heat up the engine crankcase.
• Fit the bearings in their seats in the
crankcase.
• Assemble the crankshaft in the warm
crankcase.
ENG - 121
Engine RX SX 125
NEVER TAP THE CRANKSHAFT UNIT WITH A MALLET TO

FIT IT INTO THE CRANKCASE.
Specific tooling
AP0277917 Brackets
IF THE CRANKCASE, THE CRANKSHAFT OF THE MAIN BEARING ON THE CRANKSHAFT HAVE
BEEN REPLACED, THE AXIAL CLEARANCE OF THE SHAFT NEEDS TO BE READJUSTED.
• Position the extractor plate with two
M6x16 Allen screws.
• Once the plate is positioned, tighten
the screws. Do not use the two Allen
screws used for positioning; use the
holes marked with the number three.
• Fully insert the short threaded end of
the extractor screw in the extractor
plate.
• Insert the crankshaft in the tapping of
the extractor screw by turning the shaft
clockwise until it stops.
• Push the crankshaft fully into the
crankcase by turning the extractor
screw anticlockwise. While fitting the
crankshaft, keep the connecting rod in
the direction of the cylinder axis.
• Once the fitting is complete, undo and
remove the screws fixing the extractor
plate.
• Turn the extractor screw clockwise un-
til the extractor plate starts moving up.
• Keep the extractor screw blocked and
turn the crankshaft anticlockwise, thus
removing the extractor plate unit from
the engine.
Specific tooling
crankcase halves
ENG - 122
RX SX 125 Engine
Refitting the crankcase halves
• Unscrew and remove the fixing bolt and the washer from the support.
• Apply LOCTITE Anti-Seize to each bearing seat of the shafts.
• Fit the crankcase gasket on the flywheel-side crankcase half.
• Insert the O-ring in the crankshaft.
ALWAYS USE NEW GASKETS.

NOTE
THE CRANKCASE GASKET MAY BE GREASED TO KEEP IT IN POSITION. THE CRANKCASE
GASKET MUST MATCH ALL THE HOLES ON THE CRANKCASE. OPERATE WITH CAUTION SO
THAT THE COUPLING DOES NOT LEAK.
• Warm the clutch side crankcase half at
50 - 60 °C and couple it to the flywheel
side crankcase half.
ALWAYS USE NEW GASKETS.

NOTE
THE CRANKCASE GASKET MAY BE GREASED TO KEEP
IT IN POSITION. THE CRANKCASE GASKET MUST MATCH
ALL THE HOLES ON THE CRANKCASE. OPERATE WITH
CAUTION SO THAT THE COUPLING DOES NOT LEAK.
• Fix again the crankcase to the support

by tightening the bolts.
• Screw both crankcase halves with new
M6 Allen screws.
TIGHTEN THE SCREWS CROSSWISE STARTING GRADU-

ALLY FROM THE CRANKCASE CENTRE. USE AN ADDI-
TIONAL SEALING RING ON THE COOLANT DRAINAGE
SCREW. USE A KNIFE TO CUT THE PROTRUDING SEC-
TIONS OF THE CRANKCASE GASKETS ON THE CYLIN-
DER CENTRING. OPERATE WITH CAUTION SO AS NOT
TO DAMAGE THE SEAL SURFACE.
• Fix the spring, the ring, the lever and

the washer with the M6 Allen screw.
NOTE
MAKE SURE THE LEVER MOVES SMOOTHLY.
ENG - 123
Engine RX SX 125
• Insert the gear shaft pre-assembled in

the crankcase.
SET THE GEAR TO IDLE AND MAKE SURE BOTH THE

SECONDARY AND THE MAIN SHAFTS MOVE SMOOTHLY.
ENGAGE 3rd GEAR AND TURN THE SHAFT TO LEFT AND
RIGHT UNTIL THE LATCH TOUCHES THE RELEVANT PIN
ON THE DESMODROMIC DRUM. THERE SHOULD BE THE
SAME CLEARANCE ON BOTH SIDES. IF CLEARANCES
DIFFER, FOLD THE TAB AS REQUIRED.
• Place the two countershaft control gears.
MAKE SURE ALL THE MARKS ARE ALIGNED.
ENG - 124
RX SX 125 Engine
• Fit the crankshaft control gear.
• Fit the locking seeger ring of the crank-

shaft control and that of the counter-
shaft control.
NEVER REUSE OLD SEEGER RINGS. WHEN USING A

SEEGER RING, BE CAREFUL NOT TO OVER STRETCH IT.
MAKE SURE THE RINGS ARE FULLY INSERTED IN THE
GROOVES.
Lubrication
Oil pump
ENG - 125
Engine RX SX 125
Removing
• Place the engine support so as to fa-
cilitate oil pump removal operations.
• Undo and remove the two screws fixing
the oil pump.
• Remove the oil pump and the O-ring

underneath; collect the oil pipes and
their guides.
Inspection
• Male sure the delivery (1) and intake
(2) pipes do not leak or have pores at
their connecting points. Replace if re-
quired.
• Clean the oil reservoir, the oil reservoir
filter and the oil intake pipe.
• Always replace the oil pump when
damaged or leaking.
• After installing the flexible pipe of the
oil pump, adjust it so that when in idle
position the marks on the pump lever
(3) are aligned with the pump (4) seat.
BLEEDING
Purge the oil pump and its pipes:
ENG - 126
RX SX 125 Engine
• Before riding the bike for the first time;

• Each time the engine has been operating with an empty oil reservoir;
• When the lubrication system components have been replaced.
In order to bleed the oil pump and pipes, open the oil bleed screw (5).
Drain the oil until it is completely air-bubble free.
Once the oil is fully bubble free, close the bleed screw (5) again.
With the engine running, check the delivery pipe to see if the oil pump is working properly.
SAS valve
In order to control CO and HC emissions in vehi-

cles without a lambda probe, exhaust fumes un-
dergo a post-combustion process as ambient air
(rich in O2) is supplied to the flow of burned gases .
This system is particularly necessary when the en-
gine is idling and at the warming up stage as, given
these conditions, the catalytic converter is not able
to activate the post-combustion reaction freely.
Thanks to the secondary air system - SAS-, the
post-combustion reaction is immediately activated
outside the combustion chamber, reducing CO
and HC first, and thanks to the heat produced, it
accelerates the thermal adjustment of the catalytic
converter. The SAS takes advantage of the pres-
sure fluctuation at the exhaust.
At the low-pressure stages (when cleaning), the
exhaust sucks in fresh air from the secondary air
system; the unburned gases leaving the combus-
tion chamber, warm and still active, continue and
complete combustion when in a highly oxidising
environment.
At the excess-pressure stages, the secondary air
(reed) valve closes the circuit, thus blocking return
flows.
The secondary air valve is fitted with a cut-off de-
vice, activated by a low-pressure intake on the inlet
manifold. This device cuts off the circulation of
secondary air when released to avoid excess lean-
ENG - 127
Engine RX SX 125
ing of the exhaust fumes that might cause bursts

in the muffler which may damage the exhaust
valves and the catalytic converter.
WHEN ADJUSTING CO DEACTIVATE THE SECONDARY

AIR SYSTEM AS THE EXHAUST FUMES DILUTED BY THE
SYSTEM DISTORT THE READING OF THE CARBON MON-
OXIDE PERCENTAGE.
SEE THE CO ADJUSTMENT SECTION TO DEACTIVATE
THE SAS.
AFTER ADJUSTING CO, REMEMBER TO RESTORE THE

SECONDARY AIR SYSTEM AS THE VEHICLE WORKS
REGULARLY ALSO WITH THE SYSTEM DEACTIVATED
BUT, GIVEN THESE CONDITIONS, THE HARMFUL EMIS-
SIONS INCREASE. LACK OF AIR CIRCULATION MAY AL-
SO RESULT IN OVERHEATING AND THIS IN TURN COULD
DAMAGE THE SAS COUPLINGS AND PIPING.
TO BLOCK AIR CIRCULATION USE SUITABLE SYSTEMS

ONLY; USING PLUGS TO BLOCK THE AIR INTAKE IN THE
FILTER HOUSING MAY DAMAGE THE SECONDARY AIR
SYSTEM DUE TO OVERHEATING. IF YOU FORGET A
PLUG FITTED, IT MAY GET INTO THE INTAKE DUCT WHEN
THE VEHICLE IS USED, THUS BLOCKING THE THROTTLE
VALVE AND RESULTING IN LOSS OF CONTROL OVER
THE VEHICLE.
ENG - 128
INDEX OF TOPICS
POWER SUPPLY P SUPP

Power supply RX SX 125
Circuit diagram
Key:
1. Fuel tank
2. Fuel cock
3. Oil mixer tank
4. Oil reservoir cap
5. Oil level gauge
Carburettor
Removing
• Undo the two screws.
P SUPP - 130
RX SX 125 Power supply
• Remove the throttle valve but keep it

connected to the throttle cable.
• Remove the screw.
• Remove the cold start control but keep

it connected to the cable.
• Disconnect connectors (1) and (2).
P SUPP - 131
• Working from the right side, remove

the fuel pump (3) vacuum hose and the
fuel hose (4).
• Loosen the clamps.
P SUPP - 132
• Remove the clamp and slide off the fil-

ter casing pipe.
• Choke the mix oil hose with a clamp

and remove from the carburettor.
• Rotate carburettor to the left.
• Remove the carburettor.
• To refit, follow the procedure described above but in reverse order.

• Be very careful about the correct position of the fuel pipes.
CAUTION
IF FUEL HOSES ARE INCORRECTLY POSITIONED, THIS MAY RESULT IN CRUSHED HOSES
AND THEREFORE IRREGULAR FUNCTIONING AND / OR SERIOUS ENGINE DAMAGE.
P SUPP - 133
Disassembling
Removing the carburettor
• Remove the two screws and slide off

the throttle valve / throttle valve posi-
tion sensor unit.
• Remove the heater.
• Remove the float chamber cap.
• Remove the maximum nozzle cap.
P SUPP - 134
• Remove the minimum nozzle.
• Remove the start-up nozzle.
• Remove the throttle valve position sen-

sor.
Carburettor refitting
• Make sure that the TPS gear (5) is fully

turned clockwise; the control arm (6)
should be at the fully extended posi-
tion.
P SUPP - 135
• Assemble the sensor with the fixing

eyelet to the left compared with the cor-
rect fixing position.
• Turn the sensor clockwise until the

eyelets are aligned and fix the position
with the corresponding screw.
CAUTION
ONCE THIS OPERATION IS FINISHED, THE MAXIMUM
AND MINIMUM POSITIONS OF THE THROTTLE VALVE
MUST BE OBTAINED BY MEANS OF THE RELEVANT
FUNCTION OF THE AXONE DIAGNOSIS TOOL.
Ignition
Axone use for ignition system
ignition
CAUTION
UNLESS OTHERWISE SPECIFIED, THE VALUES INDICATED ARE ONLY EXAMPLES.
ISO screen page
ISO DISPLAY
Mapping SX125_28
Map reading active 1 / 2 indicates whether the control unit is standard (1) or it has
been modified for racing on tracks (2)
Hardware code APG01
Serial number 12
Central unit hardware version B00
Software version APG1_210
Type-approval Code AC29
Engine type RS125
Reprogramming or production date 22 / 11 / 2006
P SUPP - 136
Engine parameter screen page
ENGINE PARAMETER READING

Engine revs rpm, measured with crankshaft rpm detection sensor
Throttle valve opening %, indication ranges from 0 to 100 %
Air temperature 23 °C, if signal is lost, the control unit set the value to 50 °C
Battery voltage 12 V
Ignition advance 12 °, ignition advance with respect to TDC
Warm - up time (from KEY ON) s
Vehicle speed 0 km / h
Devices activation screen page
DEVICE ACTIVATION
Deleting errors By pressing the 'enter' button, the stored errors (MEM) become
part of the historical data (STO). The next time Axone is con-
nected to the ECU, the errors in the historical record (STO) will
no longer be displayed
Coil The coil is activated five times
Outlet valve The solenoid valve is activated five times
Intake air solenoid valve The solenoid valve is activated five times
Rpm indicator The needle should be at 10000 rpm for two seconds
Speed gauge Activates the speedometer at 100 km / h
Errors display screen page

CAUTION
IF THERE IS ANY ENGINE FAILURE, THE CONTROL UNIT DOES NOT TURN ON THE EFI WARN-
ING LIGHT.
THE EFI WARNING LIGHT IS INACTIVE IN THIS VEHICLE.
THE OPERATOR WHO ENCOUNTERS A FAILURE IN THE ENGINE MUST CARRY OUT ALL THE
PRESCRIBED AXONE CHECKS WITH THE AIM OF ENSURING THE ENGINE HAS BEEN THOR-
OUGHLY CHECKED.
ERRORS DISPLAY
EEPROM : checksum error. Signal not valid Control unit internal error
Data zone EEPROM not valid : default values reset Control unit internal error
Crankshaft position sensor Circuit open An interruption has been detected between pin 9 and pin 3 of
the small connector in the control unit
Crankshaft position sensor Shorted to ground Continuity has been detected between the ground connection
and pin 9
Crankshaft position sensor Signal not valid Abnormal voltage has been detected due to an electric resist-
ance not foreseen in the circuit connecting to the revolution
sensor: between pin 9 and pin 3 of the small connector of the
control unit
Ignition capacitor Shorted to ground Error detected in the capacitor charging system in the control
unit: check that the power supply and ground connection of the
control unit are adequate
Ignition coil (circuit open) Lack of ground connection to pin 14 has been detected
No ignition Error detected in the capacitor charging system in the control
No ignition Error detected in the capacitor charging system in the control
Incorrect crankshaft signal. Signal not valid Abnormal error detected by the control unit
P SUPP - 137
Supply voltage tool low. Below the minimum level Voltage below 10 V, longer than 10 seconds has been detected
at pin 3 of the large connector in the control unit
Supply voltage tool high. Over the maximum level Voltage over 15.5 V, longer than 20 seconds has been detected
at pin 3 of the large connector in the control unit
Throttle position sensor shorted to positive Voltage about 5 V has been detected at pin 13 (throttle valve
position signal input)
Throttle position sensor Circuit open or short circuit to ground Voltage about 0 V has been detected at pin 13 (throttle position
signal input)
Throttle position sensor Out of range Voltage below the value stored by the throttle self-learning -
minimum position or over that stored by the throttle self-learn-
ing - maximum position has been detected at pin 13 (throttle
position signal input)
Outlet solenoid valve check shorted to positive High voltage has been detected at pin 1. If Map 1 is active, the
error is deactivated
Outlet solenoid valve check. Open circuit or short circuit to Too low or no voltage has been detected at pin 1. If Map 1 is
ground active, the error is deactivated
Intake manifold valve shorted to positive High voltage has been detected at pin 7 (detected only at en-
gine start-up). If Map 2 is active, the error is deactivated
Intake manifold valve. Open circuit or shorted to voltage Too low or no voltage has been detected at pin 7. If Map 2 is
active, the error is deactivated
Air temperature sensor. Short circuit to ground Too low or no voltage has been detected at pin 4. If Map 2 is
active, the error is deactivated. Whether Map 1 or 2 is active,
a recovery value of 50 °C is set
Air temperature sensor. Open circuit or short circuit to ground Excessive voltage has been detected at pin 4. If Map 2 is active,
the error is deactivated Whether Map 1 or 2 is active, a recovery
value of 50 °C is set
Adjustable parameters screen page
ADJUSTABLE PARAMETERS
Throttle self-learning, min. position It enables storing the reference value of the throttle when it is
fully in: if the voltage value detected is abnormal or variable, it
is not stored and the Axone signals this irregular situation.
Throttle self-learning, max. position It enables storing the reference value of the throttle when it is
at maximum opening position by fully twisting the throttle grip:
if the voltage value detected is abnormal or variable, it is not
stored and the Axone signals this irregular situation
P SUPP - 138
INDEX OF TOPICS
SUSPENSIONS SUSP
Suspensions RX SX 125
Front
Key:
1. Tyre
2. Air chamber
3. Wheel flap
4. Nipples
5. Rim
6. Front wheel radius
10.Hub
11.Wheel spacer
12.Bearings spacer
13.Hub bearing
14.Oil seal
15.Bare front wheel
16.TSPEI screw
17.Brake disc
18.Magnet
SUSP - 140
RX SX 125 Suspensions
19.Seeger ring
20.Front hub pin
Removing the front wheel

CAUTION
UPON REMOVING, PAY ATTENTION NOT TO DAMAGE THE BRAKE HOSES, DISCS AND PADS.
• Place the vehicle on its OPTIONAL rear service stand.
CAUTION
MAKE SURE THE VEHICLE IS STABLE.
HELPED BY ANOTHER OPERATOR, KEEP THE HANDLEBAR STEADY AND ENGAGED SO THAT
THE STEERING IS LOCKED.
• Undo and remove both front calliper
fixing screws.
• Remove the brake calliper.
CAUTION
DO NOT ACTUATE THE FRONT BRAKE LEVER AFTER
REMOVING THE WHEEL. OTHERWISE, THE CALLIPER
PLUNGERS COULD GO OUT OF THEIR SEAT, RESULTING
IN BRAKE FLUID LEAKAGE.
• Working from the right side, loosen

both screws.
• Working from the right side, unscrew

and remove the cover.
SUSP - 141
• Place a stand under the tyre to keep

the wheel in position once it is free.
• Slide off the wheel pin from the left
side.
• Collect the spacer from the left side.

• Remove the wheel by sliding it off from the front.
Checking the front wheel

CAUTION
CHECK THAT ALL THE PARTS ARE IN GOOD CONDITIONS, ESPECIALLY THOSE MENTIONED
BELOW.
BEARINGS
Turn the internal ring manually; it must rotate
smoothly, continuously and silently.
There must be no axial clearance.
The bearings presenting these problems must be
replaced.
GASKETS
Check that the gaskets are in good conditions; replace them if they show signs of damage or excessive
wear.
SUSP - 142
WHEEL PIN
Using a dial gauge, check the wheel pin eccen-
tricity. If the eccentricity exceeds the limit value,
replace the pin.
Maximum eccentricity: 0.25 mm (0.0098 in)
RIM
Using a dial gauge, check that the radial (A) and
the axial (B) eccentricities of the rim do not exceed
the limit value. An excessive eccentricity is usually
caused by worn or damaged bearings. Replace
the rim if, after replacing the bearings, the value is
not within the specified limit.
Maximum radial and axial eccentricity: 2 mm.
TYRE
Check the tyre conditions.
Installing the front wheel
• Spread a thin layer of lubricating

grease all along the wheel pin.
CAUTION
UPON REFITTING, PAY ATTENTION NOT TO DAMAGE
THE BRAKE HOSES, DISCS AND PADS.
CAUTION
POSITION THE SPACER WITH THE LARGER DIAMETER
SIDE FACING THE FORK RIGHT STEM.
• Fit the spacer in its position on the wheel.

• Fit the wheel between the fork stems, on the support.
RISK OF INJURY. BE CAREFUL NOT TO INTRODUCE YOUR FINGERS TO ALIGN THE HOLES.
SUSP - 143
• Move the wheel until the central hole is

aligned with the holes on the wheel.
• Working from the left side, insert the
wheel bolt until it stops.
• Finger tighten the cap.

• Lock the wheel pin so that it does not
rotate.
• Screw off the cap.
OPERATE WITH CAUTION SO AS NOT TO DAMAGE THE

BRAKE PADS.
• Slide the brake calliper on the disc and position it with the fixing holes aligned with the holes
on the support.
CAUTION
UPON REFITTING THE CALLIPER, REPLACE ITS FIXING SCREWS WITH NEW SCREWS OF THE
SAME TYPE.
• Screw and tighten both calliper fixing
screws.
• Operating the front brake lever, press
the handlebar repeatedly to send the
fork fully down. In this way the fork
stems will be correctly adjusted.
• Tighten the two screws of the wheel pin

clamp.
SUSP - 144
• Remove the (OPTIONAL) front service stand.

• Remove the (OPTIONAL) rear service stand.
CAUTION
AFTER REFITTING, OPERATE THE FRONT BRAKE LEVER REPEATEDLY AND CHECK THAT
THE BRAKING SYSTEM OPERATES CORRECTLY.
CAUTION
AFTER REFITTING, PULL THE BRAKE LEVER REPEATEDLY AND CHECK THAT THE BRAKING
SYSTEM OPERATES CORRECTLY.
• Check that the wheel is centred.
Front fork
Diagram
Key:
1. Complete cap
2. O-ring
3. Complete sleeve
4. Sliding bushing
5. Guide bushing cap
6. Sealing ring
7. Snap ring
SUSP - 145
8. Dust guard with clip

9. Spacer
10.Nut
11.Spring guide
12.Snap ring
13.Right pumping member rod
14.Right pumping member
15.Pin
16.Spring
17.Cap
18.Ring
19.Spring
20.Piston ring
21.Piston
22.Nut
23.Valve
24.Sliding bushing
25.Left pumping member rod
26.Left pumping member
27.Cap
28.Left piston
29.Nut
30.Right pumping member assembly
31.Left pumping member assembly
32.TE flanged screw
33.Stem + right wheel holder
34.Stem + left wheel holder
35.Spring
36.Preloading pipe
37.Sealing washer
38.TCE screw
39.Thickness
40.Thickness
41.Thickness
Removing the fork legs

CAUTION
POSITION THE OPTIONAL FRONT SERVICE STAND HIGH
CAUTION
SUSP - 146
THE FOLLOWING OPERATIONS REFER TO A SINGLE STEM BUT APPLY TO BOTH.

• Undo both locking screws of the lock
clamp placed on the brake pipe on left
stem protection.
• Release the brake pipe from the left stem protection.
• Undo both stem protection fixing

screws.
• Remove the stem protection.
• Remove the front wheel.
• Loosen the screw on the upper plate.
• Loosen both lower plate screws.
SUSP - 147
• Slide off the stem downwards, being careful not to damage its surface.
Draining oil
CAUTION
THE FOLLOWING OPERATIONS REFER TO A SINGLE WHEEL HOLDER STEM / SLEEVE BUT
APPLY TO BOTH.
• Remove the wheel holder stem / sleeve unit.
• Clean the wheel holder stem / sleeve unit thoroughly.
CAUTION
BEFORE CARRYING OUT THE OPERATIONS BELOW, GET A +440 cm³ (26.85 cu.in) CONTAINER
TO COLLECT THE OIL.
• Place the sleeve in a vice fitted with
protection shoes.
CAUTION
THE WHEEL HOLDER STEM SLEEVE UNIT CONTAINS
OIL. DO NOT TURN IT OVER OR TILT IT TOO MUCH WHEN
REMOVING IT.
• Unscrew and remove the upper cap of

the shock absorber rod.
• With an open wrench keep the lock nut

firm on the shock absorber rod and un-
lock the upper cap.
SUSP - 148
• Remove the spring preloading pipe.
• Remove the spring.
• Drain the oil off the stem being careful

not to slide the stem sleeve.
• For easy drainage of the oil inside the

cartridge, pump it several times with
the stem in vertical position.
SUSP - 149
• Drain again all the oil inside the stem.
Disassembling the fork

CAUTION
THE FOLLOWING OPERATIONS REFER TO A SINGLE WHEEL HOLDER STEM / SLEEVE BUT
APPLY TO BOTH.
• Screw the stem, on the foot side, with
a vice fitted with protection jaws to
avoid damaging it.
• Loosen the fixing screw and remove
the guide of the stem cover.
• Hold the sleeve and firmly slide it off the

stem.
• Screw the sleeve in a vice fitted with

protection jaws so as to avoid dam-
ages.
• With a plain slot screwdriver remove
the dust guard, being careful not to
damage the sleeve rim.
• The dust guards removed can not be
reused.
SUSP - 150
• Remove the snap ring inside the

sleeve using a thin screwdriver.
• With a thick plain slot screwdriver re-

move the sealing ring from its seat
carefully and operate at several points
in one third of its circumference without
damaging the oil seal and the sleeve
rim.
• To take out the sliding bushings and

the plastic spacer hit the sleeve end
hard on a wooden surface, keeping the
sleeve perpendicular to the surface.
• To take out the sliding bushings and

the plastic spacer hit the sleeve end
hard on a wooden surface, keeping the
sleeve perpendicular to the surface.
SUSP - 151
• Screw the stem, on the foot side, with

a vice fitted with protection shoes that
avoid damaging it.
• With the cartridge rod firmly in place,
unscrew and remove the bottom screw
and its gasket.
• Remove the cartridge from the fork

stem and properly clean all the com-
ponents with a suitable detergent.
Checking the components
WHEEL HOLDER STEM
SUSP - 152
• Check the sliding surface for scorings and/or scratches. These scorings can be eliminated
by rubbing them with wet sandpaper (grain 1).
• If the scorings are deep, replace the stem.
• Use a dial gauge to check that the stem bending is below the limit value.
• If over the value, replace the stem.
Bending limit: 0.2 mm

CAUTION
A BENT STEM SHOULD NEVER BE STRAIGHTENED BECAUSE ITS STRUCTURE WOULD BE

WEAKENED AND USING THE VEHICLE MAY BECOME DANGEROUS.
• Check that there are no damages and/or cracks; otherwise, replace it.
• Check that the sliding bushings are in good conditions.
• If there are signs of excessive wear or damage, replace the affected component.
CAUTION
REMOVE ANY IMPURITY IN THE BUSHINGS, TAKING CARE NOT TO SCRATCH THEIR SUR-
FACE.
Replace the following components with new ones:
- sealing ring;
- dust guard;
- O-ring gasket on the cap.
Reassembling the fork
• Check the components.

CAUTION
BE EXTREMELY CAREFUL IN ORDER THAT NO FOREIGN BODIES GET INTO THE SLEEVE OR
THE WHEEL HOLDER STEM.
NEVER REUSE OIL.
NOTE
SPREAD A THIN LAYER OF FORK OIL ON GASKETS AND BUSHINGS BEFORE REFITTING
THEM.
• Lock the sleeve on a vice in a horizon-
tal position.
• Tighten the bottom screw.
SUSP - 153
• Insert the sliding bushing (1), use the

spacer (2) to push it into the sleeve.
• Then fit another sliding bushing (3); if
required, use a buffer of suitable diam-
eter to push in into the sleeve.
SUSP - 154
• Lubricate the dust guard (6) and the oil

seal (5) with a layer of oil .
• Insert on the fork stem: the dust guard
(6), the snap ring (7), the oil seal (5)
and the guide bushing cap (4).
• Pay attention to the direction in which
the dust guard (6) and the oil seal (5)
should be placed.
SUSP - 155
• Place the stem cover guide in the

sleeve and tighten the fixing screw.
Filling oil
• Place the sleeve upright in a vice fitted

with protection jaws.
• Compress the sleeve in the stem.
Place a support under the stem in order
to leave it compressed.
• Pour part of the fork oil into the sleeve.
• Wait some minutes until the oil fills all
the ducts.
• Pour the remaining oil.
• Pump out oil a few times.
• Measure the air gap between the oil
level and the rim.
THE SLEEVE MUST BE PERFECTLY UPRIGHT IN ORDER

TO MEASURE THE CORRECT OIL LEVEL. THE OIL LEVEL
MUST BE THE SAME IN BOTH STANCHIONS.
Characteristic
Oil level (from sleeve rim, without the spring
and with stem at the end of the stroke)
150 mm (5.9 in)
• Slowly move the cartridge upwards

and downwards rod so that it is filled
with oil.
• Do so until, pulling it upwards, there is
a noticeable uniform resistance
throughout the whole stroke.
• Tighten the lock nut until it reaches the
pumping member stem.
SUSP - 156
• Take the pumping member rod fully out

of the sleeve cartridge.
• Insert the spring keeping the pumping
member rod in place.
• Insert an open key under the lock nut
to support the pumping member rod
and the spring.
• Screw the spring until it is fully inserted
into the sleeve end.
• Place the spring preloading pipe.
• Screw the upper locking cap on the

• Screw the fork upper cap up to the

• Place the upper cap on the sleeve tak-
ing care not to damage the O-ring.
• Tighten the upper cap to the prescribed
torque.
SUSP - 157
Installing the fork legs
• Insert the sleeve together with the

wheel holder stem on the lower and
upper plates.
• Insert the wheel pin through both
stems to align the holes.
• Tighten the screw that locks the lower

plate to the sleeve.
• Tighten the screw that tightens the up-

per plate to the sleeve.
SUSP - 158
• Slide off the wheel axle.

• Mount the front wheel.
• Fit the front brake calliper and tighten

the two fixing screws.
Steering bearing
Key:
1. Headstock cap
2. Washer
SUSP - 159
3. Dust guard
4. Dust guard support ring
5. Roller bearing
6. Sealing ring
7. TE screw
8. Washer
9. Fork upper plate
10.Fork lower ring nut
11.Base with headstock
12.TCE screw
13.Screw
14.U-bolt
Adjusting play
• Unscrew and remove the four screws

and collect the washers.
• Remove both U-bolts.
• Undo and remove both upper plate

screws.
• Tap the bottom side to push upwards the upper plate together with handlebar and ignition
switch / steering lock.
• Move the upper plate forwards, place a piece of cloth to avoid damaging the instrument
panel.
SUSP - 160
• Undo and remove the screw.
• Operating on both sides, loosen the

screw.
• Fully loosen the ring nut with a crescent

type wrench. Afterwards, tighten the
ring nut again to the prescribed torque,
restoring the clearance.
• Reposition the upper plate and adjust

it adequately.
• Lubricate the thread and the bushing
base in contact with the oil.
• Tighten the upper bushing.
• Loosen the bushing and tighten it again
to the prescribed torque.
SUSP - 161
• Screw and tighten the two screws.

CAUTION
ONCE THE OPERATION IS FINISHED, MAKE SURE THE
HANDLEBAR ROTATES SMOOTHLY TO AVOID DAMAG-
ING THE SLIDING GUIDES AND COMPROMISING VEHI-
CLE HANDLING.
Rear
Key:
1. Rear tyre
2. Air chamber
3. Wheel flap
4. Rear wheel rim
5. Wheel radius
6. Wheel radius
7. Wheel radius
8. Wheel radius
9. Nipples
10.Rear hub
SUSP - 162
11.Seeger ring
12.Oil seal
13.Rear wheel pin
14.Low self-locking nut
15.Washer
16.Rear wheel spacer
17.Crown
18.Low self-locking nut
19.Curved spring washer
20.TSPEI screw
21.Chain with master link
22.Bare rear wheel
23.Bearings spacer
24.Hub bearing
Removing the rear wheel
• Rest the vehicle on the specific OP-

TIONAL stands.
• Unscrew and remove the nut and re-
trieve the washer.
SUSP - 163
• Working in both sides, loosen the set

screw.
• Slide off the chain.
• Collect the chain tensioner

• Use a rubber hammer to slide off the
wheel bolt from the vehicle left side;
collect the centring shim washers and
slide off the wheel backwards.
Checking the rear wheel

CAUTION
CHECK THAT ALL PARTS ARE IN GOOD CONDITION, ES-
PECIALLY THOSE LISTED AS FOLLOWS.
BEARINGS, GASKETS, WHEEL PIN, RIM.
FLEXIBLE COUPLING
Check that the anti-vibration buffer is not damaged and/or excessively worn. Replace the buffer if nec-
essary.
SUSP - 164
Insert the anti-vibration buffer in the wheel hub.

Fit the entire final transmission unit on the wheel, manually rotate the crown gear to right and left and
check the clearance between the anti-vibration buffer and the hub. Replace the anti-vibration buffer if
excessive clearance is found.
SPROCKET
Check the toothing of the crown and the pinion. If excessive wear is found, replace: the crown, the pinion
and the drive chain.
CAUTION
REPLACE ALL THREE PARTS TO PREVENT EARLY WEAR OF NEW COMPONENTS.
Installing the rear wheel
• Position the rear wheel.

• Position the chain.
• Working on both sides, insert the centring shim washers.
• Working from the left side, insert the wheel axle.
CAUTION
DO NOT INVERT THE RIGHT AND THE LEFT CHAIN TENSIONERS.
• Working on the right side, position the washer and screw but do not tighten the wheel axle
fixing nut.
• Adjust the chain tension operating the set screws.
CAUTION
AFTER REFITTING, OPERATE THE REAR BRAKE LEVER REPEATEDLY AND CHECK THAT THE
BRAKING SYSTEM OPERATES CORRECTLY.
CAUTION
CHECK THAT THE WHEEL IS CENTRED.
• Tighten the wheel axle fixing nut.
See also
Adjusting
SUSP - 165
Shock absorbers
KEY
1. Shock absorber
2. Single connection rod
3. Double connecting rod
4. TCEI M10x55 screw
5. 10.5x21x2 washer
6. M10 Flanged self-locking nut
7. TE flanged M10x61 screw
8. D18x24x3 oil seal
9. Roller casing
10.L=36 pin
11.Spacer
12.TCEI M12x107 screw
SUSP - 166
13.12.2x22x2 Plain iron washer

14.M12 lower self-locking nut
15.TE flanged screw M6x20
16.Bushing
17.Clip M6
Adjusting
The rear shock absorber standard setting is adjusted to suit most low speed riding conditions, whether
the vehicle is partially or fully loaded.
However, this setting can be personalised to meet specific needs according to vehicle use.
CAUTION
ALLOW ENGINE AND SILENCER TO COOL OFF BEFORE OPERATING THE SET SCREWS.
THE SET NUT MUST NOT BE TIGHTEN OVER 25 mm (0.98 in) FROM THE BEGINNING OF THE
THREAD. IF SUCH DISTANCE IS EXCEEDED, THERE WILL BE SOME JERKING WHILE RIDING
EVEN ON SOME SLIGHTLY UNEVEN ROADS.
• Operate on the set nut (1) (shock ab-
sorber spring preloading adjustment).
CAUTION
TURN THE SET NUT (1) GRADUALLY ONE TURN AT A
TIME.
TRY RIDING THE VEHICLE ON THE STREET UNTIL THE
OPTIMUM ADJUSTMENT IS OBTAINED.
REAR SHOCK ABSORBER ADJUSTMENT

By tightening the set nut (1) Spring (2) preloading increases
The scooter suspension is very hard.
Advisable for smooth or ordinary roads and when riding with
passenger.
By loosening the set nut (1) Spring (2) preloading decreases
The vehicle suspension is very soft.
Advisable for uneven roads, without passengers.
SUSP - 167
Removing
• Place the vehicle on its OPTIONAL

front service stand.
• Remove both central side fairings.
• Support the vehicle rear part using
belts and hoist.
• Place a support between the swingarm
and the saddle post frame so that the
shock absorber is in neutral position.
• Working from the vehicle left side, un-
screw and remove the link rod screw
and collect the nut from the right side.
• Working from the left side, unscrew

and remove the rear shock absorber
fixing screw and collect the nut from the
opposite side.
• Carefully place the fork upper part.
• Undo the upper screw and remove it

from the left side.
• Slide the rear shock absorber down-
wards.
SUSP - 168
Installing
SHOCK ABSORBER FITTING
• Fit the shock absorber by inserting

from the bottom.
• Insert the shock absorber upper screw
with the washer from the left side.
• Working from the opposite side, tighten
the nut (1).
• Position the connecting rod assembly

on the shock absorber.
• Insert the shock absorber lower screw
from the right side.
the nut (2).
• Place the double connecting rod in its

seat on the chassis.
• From the left side insert the nut fixing
the connecting rod assembly plus the
washer in the chassis.
the nut (3).
• Remove the support between the
swingarm and the saddle post frame.
Linkages
SUSP - 169
Removing
• Working from the right side, unscrew

and remove the nut (1).
• Slide off the screw from the opposite
side and collect the washer.

side.
• Remove the complete suspension
connecting rod assembly unit.
CONNECTING ROD ASSEMBLY REMOVAL
• Remove the complete suspension

connecting rod assembly unit.
• Unscrew and remove the nut (4).
• Remove the single connecting rod.
• Remove the right bushing (5) and the
left bushing (6) from the single con-
necting rod.
SUSP - 170
• Remove the oil seals (7) from the dou-

ble connecting rod.
• Slide off the pin (8).
• Using a specific extractor, take out the
ball retainer (9).
• Remove the belleville spring (10).
• Remove the sealing ring (11).
• Remove both oil seals (12).
ball retainer (14).
• Remove both sealing rings (15).

• Remove both oil seals (16).
ball retainer (18).
CAUTION
WASH ALL THE PARTS WITH CLEAN DETERGENT.
Checking
CAUTION
CHECK THAT NO COMPONENT IS NOTICEABLY DISTORTED, DAMAGED, CRACKED AND/OR
DENTED.
REPLACE ALL DAMAGED COMPONENTS.
BALL RETAINER
Turn the ball retainers manually; they must rotate smoothly, continuously and silently.
Replace the ball retainers that present these problems.
Apply grease on the rollers.
GASKETS
wear.
SUSP - 171
INDEX OF TOPICS
CHASSIS CHAS
RX SX 125 Chassis
Swinging arm
KEY
1. Swingarm
2. Chain guard
3. Chain guide slider
4. Slider cap
5. TCB M4.8x13 screw
6. Swing arm pin
7. 22x28x16 Roller casing
8. Sealing ring
9. D15x22x1 knurled washer
10.M14x1.5 lower nut
11.Swing arm pin bushing
CHAS - 173
Chassis RX SX 125
12.Thrust washer
13.grey rear chain guide
15.T-shaped bushing
16.M6 lower self-locking nut
17.Rh chain tensioner
18.Lh chain tensioner
19.Chain tensioner set screw
20.M8 lower nut
21.TBEI flanged M5x12 screw
Removing
CAUTION
HOLD THE VEHICLE STEADY WITH THE OPTIONAL SERVICE STAND FROM THE FRONT AND
BELTS ATTACHED TO AN OPTIONAL HOIST FROM THE REAR.
• Fasten the belts to the chassis at the
engine upper support.
• Lift the hoist arm until the belts are taut.
• Remove the chain.
• Remove the rear wheel.
and remove the nut (1) and collect the
washer.
side.
• Remove the connecting rod assembly
from the swingarm.
• Undo and remove the internal screw
(2).
• Detach the pipe clamp still attached to
the rear brake pipe from the swingarm.
CHAS - 174
RX SX 125 Chassis
• Undo and remove the external screw

(3).
• Detach the pipe clamp still attached to
the rear brake pipe from the swingarm.
• Undo and remove the screw and re-

move the speed sensor.
• Loosen the screw fixing the chassis on

the engine (4) to facilitate removing the
swingarm.
• Working from the right side, fully loos-

en the ring nut (5) with the specific box-
spanner.
Specific tooling
CHAS - 175
Chassis RX SX 125
• Working from the left side, undo and

remove the swingarm pin (7) and col-
lect the two washers.
• With the help of a second operator, re-
move the swingarm from the chassis.
SWINGARM REMOVAL
• Remove the swingarm

• Place the swingarm on a supporting
surface.
• Clean the two sides of the bearing
seats with a cloth.
• Remove the external plastic washers
(8).
• Slide off both needle bearing (11)
bushings from inside the swingarm.
• Take out the two O-rings (9).
• Using a buffer of suitable diameter take
out the two roller casings (10).
Checking
CAUTION
CHECK THAT NO COMPONENT IS NOTICEABLY DISTORTED, DAMAGED, CRACKED AND/OR
DENTED.
REPLACE ALL DAMAGED COMPONENTS.
ROLLER CASINGS
Turn the roller casings manually; they must rotate smoothly, continuously and silently.
Replace the roller casings that present these problems.
Apply grease on the rollers.
GASKETS
wear.
CHAS - 176
RX SX 125 Chassis
SWINGARM PIN
With a dial gauge check if the pin eccentricity ex-
ceeds the limit value. Otherwise, replace the pin.
Maximum pin eccentricity: 0.3 mm (0.01 in)
Installing
CAUTION
REPLACE BOTH ROLLER CASINGS
• Clean all the swingarm coupling com-
ponents completely and grease them
with lithium grease.
• Using a buffer of suitable diameter as-
semble the two new roller casings (3)
centring them axially in their housing.
• Fit the two O-rings (2).
• Fit both needle bearing (4) bushings
inside the swingarm.
• Fit the external plastic washers (1).
CAUTION
DUE TO THE REARCARRIAGE WEIGHT, THE FOLLOWING OPERATIONS REQUIRE THE INTER-
VENTION OF A SECOND OPERATOR.
• Place the swingarm on the chassis.
• Move it into position so that the holes
are aligned and, at the same time fully
insert the pin (5) from the left side.
CHAS - 177
Chassis RX SX 125
• The correct adjustment of the swing-

arm pin clearance is obtained by prop-
erly seating the ring nut set bushing (6)
and screwing it another 1 / 4 of a turn.
• Firmly hold the bushing (6) and tighten
the ring nut (7) using a special tool.
Specific tooling
• Now adjust the rear swingarm as fol-
lows:
- Loosen the pin (1), working from the left side.
- Working from the right side, fully loosen the ring

nut (6) with the specific box-spanner.
- Tighten the set bushing (6) to the prescribed tor-
que
- Use the specific box-spanner to tighten the ring
nut (7).
- Tighten the pin.
• Tighten the chassis fixing screw (8) on

the engine.
CHAS - 178
RX SX 125 Chassis
• Place the connecting rod assembly on

the swingarm.
• Insert the screw from the right side.
• Fit the washer and tighten the nut (9).
• Position the brake hoses on the swing-

arm.
• Fasten the internal brake pipe clamp
with the screw (10).
• Fasten the brake hose guide with the

screw (11).
• Mount the rear wheel.
• Assemble the chain.
• Lower the hoist arm.
• Release the belts from the chassis.
• Install the fuel tank.
• Place the speed sensor.
Drive chain
CHAS - 179
Chassis RX SX 125
Removing
• Loosen the chain tension.

• Rotate the rear wheel until the master
link can be identified.
• Slide off the clip.
• Remove the plate underneath.
• Remove the master link from the op-

posite side.
• Remove the chain.
CAUTION
REPLACE THE ENTIRE UNIT IF THE CHAIN IS PARTICU-
LARLY WORN.
inspection
Also check the following parts and make sure that the chain, pinion and crown do not present:
- Damaged rollers.
- Loose pins.
- Dry, rusty, flattened or jammed chain links.
- Excessive wear.
- Excessively worn or damaged pinion or crown teeth.
CAUTION
IF THE CHAIN ROLLERS ARE DAMAGED AND / OR THE PINS ARE LOOSE, THE ENTIRE CHAIN
UNIT (PINION, CROWN AND CHAIN) SHOULD BE REPLACED.
LUBRICATE THE CHAIN ON A REGULAR BASIS, PARTICULARLY IF YOU DETECT DRY OR
RUSTY PARTS.
FLATTENED OR JAMMED CHAIN LINKS SHOULD BE LUBRICATED AND GOOD OPERATING
CONDITIONS RESTORED.
CHAS - 180
RX SX 125 Chassis
• Check the chain tensioner roller for

wear.
• Finally, check the swingarm protection
pad for wear.
Installing
• Check the correct positioning of the

chain on the pinion and the sprocket.
• Fit the chain with the two ends joined
at a point between the pinion and the
sprocket on the lower branch of the
chain.
• Join the two ends of the chain and fit
the master link pins from the inside to
the outside.
• Insert the plate on the pins.
• Fit the clip on the pins.

CAUTION
THE MASTER LINK CLIP MUST BE FITTED WITH ITS OPEN
SIDE FACING DIRECTION OPPOSITE THE CHAIN FOR-
WARD MOVEMENT.
Adjusting
To check backslash:
• Stop the engine.

• Place the vehicle on its stand.
• Set the gear level to neutral.
• Check that the vertical oscillation, between the pinion and the crown in the lower chain
branch, is about 25 - 35 mm (0.99 - 1.38 in)
CHAS - 181
Chassis RX SX 125
• Move the vehicle forward so as to also check the chain vertical oscillation in other positions;
clearance should remain constant during all wheel rotation phases.
CAUTION
IF CLEARANCE IS GREATER AT SOME POSITIONS, THIS MEANS THAT SOME CHAIN LINKS
ARE FLATTENED OR JAMMED.
TO AVOID RISK OF SEIZURE, LUBRICATE THE CHAIN ON A REGULAR BASIS.
Adjust backlash if it is uniform but over or below 25
- 35 mm (0.99 -1.38 in), adjust it.
CAUTION
GET A SPECIFIC REAR SERVICE STAND (OPT) TO ADJUST THE CHAIN.
If chain tension needs adjusting after the check:
• Place the scooter on its rear service

stand (OPT).
• Loosen the nut (1) completely.
WHEEL CENTRING IS CARRIED OUT USING IDENTIFIA-

BLE FIXED REFERENCES (2-3) IN THE TENSIONER
MOUNTS ON THE SWING ARMS BEFORE THE WHEEL
PIN.
• Loosen both lock nuts (4).

• Actuate on the set screws (5) and ad-
just the chain backlash checking that
the references (2 - 3) match on both
sides of the vehicle.
• Tighten both lock nuts (4).
• Tighten the nut (1).
• Wheel nut tightening torque (1):
Locking torques (N*m)

Rear wheel fixing pin 100
Chain sliders
CAUTION
FOR SPACE REASONS DETACH THE CHAIN.
CHAS - 182
RX SX 125 Chassis
• Undo and remove the upper screw (2)

and collect the nut (6).
• Undo and remove the screw (3) and
collect the rubber ring (5).
• Remove the upper chain guide slider
(4).
• Undo and remove the two lower
screws (2).
• Remove the lower chain guide slider
(1).
Exhaust
KEY
1. Muffler
CHAS - 183
Chassis RX SX 125
2. Silencer
3. Silencer clamp
4. Muffler protection
5. Silent-block
6. M6 Flanged self-locking nut
7. Insulating washer
8. Clip M6
9. TE flanged screw M6x16
10.Traction cyl. helical spring
11.TCEI M6x16 screw
12.Silencer plate
13.M6x12 TE flanged screw
14.6.4X11X0.5 spring washer
15.6.6x18x1.6 washer
16.Insulating washer
17.Central exhaust pipe
18.Silencer gasket
19.Lower self locking nut
20.Pull screw
21.Plate
22.Washer
Removing the tail pipe
• Rotating it on the screw, move the fair-

ing that covers the chassis.
• Undo and remove the front fixing screw
of the silencer pipe and collect the
washer.
CHAS - 184
RX SX 125 Chassis
• Undo and remove both screws that fix

the silencer support bracket to the
chassis and collect the washer.
• Slide off the silencer backwards.
See also
Side body panels
Removing the exhaust manifold
• Undo and remove the screw that fixes

the muffler to the chassis and collect
the washer.
• Release the two cylinder attachment

springs.
• Release the secondary air pipe sealing

clamp and slide off the pipe.
CHAS - 185
Chassis RX SX 125
• Undo and remove the two fixing nuts of

the manifold and collect bracket and
washer.
• Slide off the muffler forwards.

CAUTION
WHEN REFITTING, REPLACE THE EXHAUST GASKET AND CHECK THE CORRECT POSITION-
ING OF THE FIXING BRACKETS.
Rave valve
The exhaust valve is operated by a solenoid through a flexible cable.

The solenoid is enabled within a given range of the electric control unit that receives the engine rotation
signal from the primary circuit frequency.
CAUTION
FITTING THE EXHAUST VALVE ON 11 KW HOMOLOGATED VEHICLES RENDERS SUCH CER-
TIFICATION INVALID. IT CAN ONLY BE USED FOR RACING OR ON RACETRACKS AND CIR-
CUITS NOT OPEN TO THE PUBLIC.
RAVE operation
• The exhaust valve opens between 500 and 2500 rpm for the valve stem self-cleaning.
• It closes between 2500 rpm and the actuation point (about 8000 rpm).
• It remains open beyond the actuation point.
RAVE valve actuation points

8000 rpm
CHAS - 186
RX SX 125 Chassis
The solenoid controlled by the rave control unit opens the exhaust valve at 8000 rpm.
TROUBLESHOOTING
• Check that the 7.5 A fuse is in good

conditions.
• Check the if the solenoid is working
properly by powering it directly with a
12 V battery.
• Check the flywheel
• Replace the regulator with another one
in proper operating conditions.
• Replace the EFI control unit with an-
other one in proper operating condi-
tions.
CAUTION
THE RAVE VALVE CHECKING FUNCTION IS ACTIVATED
WHEN THE EFI CONTROL UNIT JUMPER IS CUT OFF.
SOLENOID
• Check that the piston moves freely.

• Measure the resistance between the wires with a tester:
• Correct value = 2.2 Ohm + / - 10%.
• Start the vehicle, go over 6500 rpm
• Let the engine idling
CHAS - 187
Chassis RX SX 125
• Check that the solenoid activates the RAVE at 0.5-sec pulse intervals.
Removing
• Remove the fuel tank

• Remove the battery with the battery
housing.
PARTIAL
• Detach the protection casing (1).

• Undo and remove both screws (2) and
collect the locking washers.
If the valve moves freely:
• Take out the exhaust valve unit togeth-

er with the flexible cable from the cyl-
inder.
• Turn the stem valve (3) seat by 180°
and disconnect the flexible cable (4).
• If the exhaust valve is blocked at the
opening position (due to combustion
deposits):
• Push the valve stem (3) housing back
with a screwdriver.
CAUTION
PAY ATTENTION NOT TO DAMAGE THE SEAL SUR-
FACE.
• Turn the stem valve (3) seat by 180°

and disconnect the flexible cable (4).
• Remove the stem valve (3) housing
and collect the spring (6) and the gas-
ket (5).
• Take out the exhaust valve (7) using
the specific valve extractor
CHAS - 188
RX SX 125 Chassis
TOTAL
• Undo and remove both RAVE valve

screws and collect the locking wash-
ers.
• Take out the exhaust valve unit from
the cylinder.
• Disconnect the connector of the sys-

tem control unit.
• Undo and remove both screws (8) from

the battery housing frame.
• Remove the whole RAVE valve.
Checking
GASKETS
• Check that the valve gasket (1) and the O-ring (2) (fitted to the valve seat) are not worn or
damaged.
EXHAUST VALVE
• Clean off any combustion deposits from the exhaust valve (3) and from the valve duct in the
cylinder.
• Make sure that the exhaust valve is not worn or damaged.
CHAS - 189
Chassis RX SX 125
CYLINDER GASKET
The cylinder gasket (4) must be replaced at every
refitting operation.
SOLENOID
• Check the control unit as per the dia-

gram.
Installing

• Remove the battery with the battery
housing.
• If the vehicle is a crossover version, re-
move the fixed guillotine by undoing
the two screws (1) and collect the
washers before fitting the RAVE valve.
TOTAL
• Insert the exhaust valve unit with the

gasket (5) in the cylinder.
CAUTION
REPLACE THE GASKET (5) AT EVERY REFITTING OPER-
ATION.
• Fit the exhaust valve unit by means of the two screws (1) with the fixed guillotine washers.
• Fit the control unit with the two screws

(2) on the battery housing frame.
CHAS - 190
RX SX 125 Chassis
• Connect the connector of the control

unit to the system.
• Connect the flexible cable (3) to the

stem valve housing (4).
• Rotate the stem valve housing (4) by
180°.
CAUTION
THE CABLE CONNECTION SHOULD BE FACING DOWN-
WARDS..
• Refit the protection casing.

• Insert the exhaust valve unit with the gasket (5) in the cylinder.
CAUTION
REPLACE THE GASKET (5) AT EVERY REFITTING OPERATION.
• Tighten the two exhaust valve unit screws (1) with their washers.
CAUTION
AFTER FITTING THE EXHAUST VALVE UNIT, CHECK:
- With the valve fully open, the valve stem end
should be at the same level with the exhaust port.
To do so, it is necessary to remove the exhaust
flange.
- make sure that the exhaust valve moves freely.
CHAS - 191
INDEX OF TOPICS
COOLING SYSTEM COOL SYS

RX SX 125 Cooling system
Circuit diagram
KEY
1. RH Radiator
2. Radiator cap
3. LH Radiator
4. T-shaped bushing
5. 11.5x23x9.3 rubber cap
6. Clip M6
7. Radiators water pipe
8. Radiator-pump pipe
9. D24.24.5x8.6 clic clamp
10.Head-radiator pipe
11.d.7x11 fuel pipe
COOL SYS - 193

Cooling system RX SX 125
12.D11x6.6x1 green clic clamp

13.D28x8.6 clic clamp
14.D23.5x8 clic clamp
15.D23.5x8 clic clamp
16.D10.1 clamp
17.5x9 pipe
Coolant replacement
CAUTION
DO NOT USE YOUR VEHICLE IF THE COOLANT IS BELOW THE MINIMUM LEVEL.
CHECK THE COOLANT LEVEL PERIODICALLY OR AFTER LONG TRIPS.
• Remove both front side fairings.
• Place a container of suitable capacity
underneath the sleeve.
• Release the clamp.
• Slide off the sleeve.

• Empty the liquid into the container.
• Open the radiator cap to facilitate
drainage.
• Unscrew and remove the drainage

plug (1) indicated by the mark OUT.
• Unscrew and remove the radiator plug
to facilitate draining the coolant.
CAUTION
DO NOT DISPOSE OF THE FLUID INTO THE ENVIRON-

MENT.
• Wait for the coolant to drain off and tighten the screw.
COOL SYS - 194

• Top-up with coolant.

CAUTION
DO NOT DISPOSE OF THE FLUID INTO THE ENVIRONMENT.

See also
Side body panels
Water pump
• Remove the water pump control gear.
• Undo and remove the M5 fixing screw.
• Slide off the water pump gear.
COOL SYS - 195

• Remove the water pump with the help

of a square screwdriver.
REFITTING
• Upon refitting follow the removal steps but in reverse order, paying special attention to the
alignment of the water pump control wheel, which must be aligned with the reference on the
crankcase when refitting.
Removing the radiator
• Remove both front side fairings.

underneath the sleeve.
• Release the clamp.
• Slide off the sleeve.

• Empty the liquid into the container.
• Open the radiator cap to facilitate
drainage.
COOL SYS - 196

• Working on both sides, release the

clamps between the aluminium tube
and the rubber hose in the radiator.
• Remove the right and left delivery

pipes.
• Remove the radiator breather pipe.
• Working on both sides, undo the two

screws and collect the spacer.
COOL SYS - 197

• Operating on both sides of the chassis,

undo and remove the two screws and
collect the washers and remove the ra-
diator.
CAUTION
THE RADIATORS ARE INTERCONNECTED THROUGH
THE LOWER PIPE.
COOL SYS - 198

INDEX OF TOPICS
BODYWORK BODYW
Bodywork RX SX 125
Seat
• Place the vehicle on the service stand.

• Insert the key in the lock.
• Turn the key anticlockwise.
• Lift and remove the saddle.
UPON REFITTING:
BEFORE LOWERING AND LOCKING THE SADDLE,
CHECK THAT THE KEY HAS NOT BEEN LEFT INSIDE THE
GLOVE-BOX / TOOLKIT COMPARTMENT.
• Fit the saddle making sure to position

the corresponding rear hooks correct-
ly.
• Lower and press the saddle to trip the
lock.
BEFORE RIDING, MAKE SURE THAT THE SADDLE IS

CORRECTLY LOCKED INTO POSITION.
Headlight assy.
• Undo and remove both screws on the

upper plate.
• Undo and remove the two screws fas-

tening the mudguard and collect the
nuts and washers from the bottom.
BODYW - 200
RX SX 125 Bodywork
• Slide off the front brake pipes from the

hose guide.
• Remove the headlight assembly for-
wards, releasing it carefully from the
front fitting slots on the mudguard.
• Remove the rubber cap and discon-

nect the instrument panel connector.
• Disconnect the front headlight bulb

connectors.
Taillight assy.
• Remove the tail and the rear side fair-

ings.
• Disconnect the turn indicators connec-
tors (1), license plate light (2), rear light
(3).
• Remove the clamp (4).
BODYW - 201
Bodywork RX SX 125
TURN INDICATORS
• If necessary, remove the turn indica-

tors working from any side, then undo
and remove the screw and carefully
slide off the gauge with cables.
LICENSE PLATE LIGHT
• If necessary, remove the license plate

light, undo and take out the screw and
carefully slide off the light with cables.
REAR LIGHT
• If necessary remove the rear light, un-

do and take out both screws and collect
the washers.
• Slide off the rear light with cables care-
fully.
Side body panels
CENTRAL FAIRING
The following operations refer to only one fair-
ing but are valid for both.
• Unscrew and remove the screw and

collect the collar.
BODYW - 202
RX SX 125 Bodywork
• Unscrew and remove the screw and

collect the collar.
• Undo and remove the lower screw.
• Remove the central side fairing.
FRONT FAIRING
• Remove saddle, central fairings and

tank cover.
• Undo and remove the right-side screw
and collect the nut from the left side.
BODYW - 203
Bodywork RX SX 125
• Undo and remove the fixing screw.
The following operations refer to only one fair-

ing, but are valid for both.
• Undo and remove the radiator fixing

screw.
• Remove the front side fairing.
CHASSIS COVER
• They are placed in the central area on

both sides of the vehicle. For regular
operations remove the three clamps
and turn the cover according to visibil-
ity requirements, acting on the lower
screw slightly loose.
If necessary, remove them from the vehicle:
• Remove the three retaining clamps.
BODYW - 204
RX SX 125 Bodywork
• Undo and remove the lower screw,

paying attention to the rear brake lever
placed on the right-hand side.
Upon refitting, replace clamps with the same type

and size of clamps.
See also
Seat
Fuel tank
Air box
• Support the vehicle with a suitable under-sump stand.

• Support the scooter rearcarriage with a hoist and suitable belts.
• Remove the saddle.

• Remove both central fairings.
• Remove the six chassis side cover
clamps and loosen the lower screws to
rotate the cover rightwards.
• Working from the right side, undo and

remove the screw and collect the collar
and the rubber ring.
BODYW - 205
Bodywork RX SX 125
• Working from both sides, undo and re-

move the screw and collect the wash-
er.
• Remove the clamp and slide off the

piping.
• Loosen the clamp and release the

sleeve.
• Undo and remove the two screws and

move the control unit sideways.
BODYW - 206
RX SX 125 Bodywork
• Remove the clamp.
• Release the fuses housing from the fil-

ter casing sliding it upwards.
• Release the relay from the filter casing
sliding it rightwards.
• Disconnect the connector.
• Remove the chassis clamp.
BODYW - 207
Bodywork RX SX 125
• Operating from both sides, undo and

remove the chassis fixing screw and
collect the nut.
CAUTION
ONCE THE CHASSIS IS RELEASED PAY ATTENTION TO
THE REAR SIDE OF THE MOTORCYCLE AND PLACE IT ON
THE GROUND LOWERING THE HOIST.
• Slide the filter casing upwards.
Fuel tank
TANK COVER

• Undo and remove the two screws.
• Undo and remove the front screw.
• Disconnect the fuel vapour recovery

pipe.
• Unscrew and remove the fuel tank cap.
• Remove the fuel tank cover and screw the cap again.
See also
BODYW - 208
RX SX 125 Bodywork
Seat
• Remove the front side fairings and the

tank cover.
• Undo and remove the two screws pay-
ing attention to the corresponding col-
lars and spacers.
• Lift the tank from the side and close the

fuel supply valve.
• Disconnect the fuel pump connector.
• Loosen the clamp and detach the pipe.
See also
Side body panels
BODYW - 209
Bodywork RX SX 125
Front mudguard
• Undo and remove the two screws and

collect the washers.
• Undo and remove the two upper

screws and collect the nuts (1) and
washers.
• Unscrew and remove the four screws
(2) and collect the washers.
• Slide off the front mudguard forwards,

paying attention to the front fitting slots.
Mixture oil tank
• Remove saddle, central right and left

fairings and right chassis cover.
BODYW - 210
RX SX 125 Bodywork
• Lift the fuel tank without removing it.

• Disconnect the oil level probe connec-

tors.

underneath the vehicle.
• Loosen the clamp and drain the reser-
voir in the container.
REFITTING
EACH TIME THE MIX OIL RESERVOIR IS DRAINED, REFILL AND BLEED.
• Mount the mix oil reservoir following
the same removal procedure but in re-
verse order.
• Undo and remove the three pump
screws on the LHS of the vehicle and
remove the cover.
• Remove the bleed screw indicated.
• Pour oil in the reservoir until air bubbles
are no longer formed in the pipe.
BODYW - 211
Bodywork RX SX 125
• Tighten the bleed screw again and fill

the reservoir until the oil reaches the
recommended level.
Battery
BATTERY REMOVAL

• Make sure the ignition switch is set to
«OFF».
• Disconnect the negative ( -) lead first
and then the positive (red) (+) one.
• Remove the battery breather pipe.
• Remove the battery from its housing
and put it away on a level surface in a
cool and dry place.
CAUTION
ONCE REMOVED THE BATTERY MUST BE PUT AWAY IN

A SAFE PLACE AND OUT OF THE REACH OF CHILDREN.
Tail guard
• Remove the saddle and the central

side fairings.
• Undo and remove the two screws.
• Undo and remove the two lower

screws.
BODYW - 212
RX SX 125 Bodywork
• To detach the rear fairings from the tail

section, check the fittings alongside
the rim, from the lower side of the tail.
• Remove fairings and tail.
BODYW - 213
INDEX OF TOPICS
PRE-DELIVERY PRE DE
RX SX 125 Pre-delivery
Carry out the listed checks before delivering the motorcycle.

WARNING
HANDLE FUEL WITH CARE.
Aesthetic inspection
- Paintwork
- Fitting of Plastic Parts
- Scratches
- Dirt
Tightening torques inspection
- Safety fasteners:
front and rear suspension unit
front and rear brake calliper retainer unit
front and rear wheel unit
engine - chassis retainers
steering assembly
- Plastic parts fixing screws
Electrical system
- Main switch
- Headlamps: high beam lights, low beam lights, tail lights (front and rear) and their warning lights
- Headlight adjustment according to regulations in force
- Front and rear stop light switches and their bulbs
- Turn indicators and their warning lights
- Instrument panel lights
- Instrument panel: fuel and temperature indicator (if present)
- Instrument panel warning lights
- Horn
- Electric starter
- Engine stop via emergency stop switch and side stand
- Helmet compartment electrical opening switch (if present)
PRE DE - 215
Pre-delivery RX SX 125
- Through the diagnosis tool, check that the last mapping version is present in the control unit/s and, if
required, program the control unit/s again: consult the technical service website to know about available
upgrades and details regarding the operation.
CAUTION
TO ENSURE MAXIMUM PERFORMANCE, THE BATTERY MUST BE CHARGED BEFORE USE.

INADEQUATE CHARGING OF THE BATTERY WITH A LOW LEVEL OF ELECTROLYTE BEFORE
IT IS FIRST USED SHORTENS BATTERY LIFE.
CAUTION
UPON INSTALLING THE BATTERY, ATTACH THE POSITIVE LEAD FIRST AND THEN THE NEG-
ATIVE ONE, AND PERFORM THE REVERSE OPERATION UPON REMOVAL.
WARNING
THE BATTERY ELECTROLYTE IS POISONOUS AS IT MAY CAUSE SERIOUS BURNS. IT CON-

TAINS SULPHURIC ACID. AVOID CONTACT WITH YOUR EYES, SKIN AND CLOTHING.
IN CASE OF CONTACT WITH YOUR EYES OR SKIN, WASH WITH ABUNDANT WATER FOR AP-
PROX. 15 MIN. AND SEEK MEDICAL ATTENTION IMMEDIATELY.
IF ACCIDENTALLY SWALLOWED, IMMEDIATELY DRINK LARGE QUANTITIES OF WATER OR
VEGETABLE OIL. SEEK IMMEDIATE MEDICAL ATTENTION.
BATTERIES PRODUCE EXPLOSIVE GASES; KEEP CLEAR OF NAKED FLAMES, SPARKS OR
CIGARETTES. VENTILATE THE AREA WHEN RECHARGING INDOORS. ALWAYS WEAR EYE
PROTECTION WHEN WORKING IN THE PROXIMITY OF BATTERIES.
CAUTION
NEVER USE FUSES WITH A CAPACITY HIGHER THAN THE RECOMMENDED CAPACITY. USING
A FUSE OF UNSUITABLE RATING MAY SERIOUSLY DAMAGE THE VEHICLE OR EVEN CAUSE
A FIRE.
Levels check
- Hydraulic braking system fluid level
- Clutch system fluid level (if present)
- Gearbox oil level (if present)
- Transmission oil level (if present)
- Engine coolant level (if present)
- Engine oil level
- Mixer oil level (if present)
Road test
- Cold start
- Instrument panel operation
PRE DE - 216
RX SX 125 Pre-delivery
- Response to throttle control

- Stability when accelerating and braking
- Front and rear brake efficiency
- Front and rear suspension efficiency
- Abnormal noise
Static test
Static check after test drive:

- Restarting when warmed up
- Starter operation (if present)
- Minimum holding (turning the handlebar)
- Uniform turning of the steering
- Possible leaks
- Radiator electric fan operation (if present)
Functional inspection
- Hydraulic braking system

- Stroke of brake and clutch levers (if present)
- Clutch - Check for correct operation
- Engine - Check for correct general operation and absence of abnormal noise
- Other
- Documentation check:
- Chassis and engine numbers check
- Supplied tools check
- License plate fitting
- Locks checking
- Tyre pressure check
- Installation of mirrors and any possible accessories
NEVER EXCEED THE RECOMMENDED INFLATION PRESSURES AS TYRES MAY BURST.

CAUTION
CHECK AND ADJUST TYRE PRESSURE WITH TYRES AT AMBIENT TEMPERATURE.
PRE DE - 217
A
Air filter: 28
Air temperature sensor: 65
B
Battery: 57, 64, 212
Brake:
Bulbs:
C
Carburettor: 130
Chain: 179, 182
Clutch: 31, 101–104
Coil: 66
Connectors: 67
coolant: 194
Coolant: 194
Crankcase: 113, 117, 123
Crankshaft: 113, 116, 121
Cylinder: 105–108, 110–112
D
Desmodromic drum: 91
Display: 137
Drive chain: 179
E
ECU: 67
Electrical system: 12, 37, 39, 215
Exhaust: 183, 185
Exhaust manifold: 185
F
Fairings: 33
Fork: 145, 146, 150, 153, 158
Front wheel: 141–143
Fuel: 205, 208
Fuses: 63
G
Gearbox oil: 26
H
Handlebar:
Head cover: 105, 113
Headlight: 33, 200
Horn: 60
I
Identification: 10
Instrument panel:
L
Linkages: 169
M
Magneto flywheel: 95, 96
Maintenance: 8, 25
Maintenance Table:
Mudguard: 210
P
Primary shaft: 91
R
Radiator: 196
Rear wheel: 163–165
Recommended products: 17
S
Secondary shaft: 91
Shock absorber:
Shock absorbers: 166
Side fairings:
Spark plug: 25
Speed sensor: 64
Stand:
Starter motor: 94
T
Tank: 205, 208, 210
Transmission: 12
Tyres: 14
V
Voltage regulator: 59
W
Warning lights:
Water pump: 195
Wiring diagram: 49

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Aprilia SX 125 Workshop Manual

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What is the purpose of this manual?

What is the purpose of this manual?

What safety precautions should be taken when working with batteries?

What safety precautions should be taken when working with batteries?

SERVICE STATION MANUAL

SPECIAL TOOLS S-TOOLS

ELECTRICAL SYSTEM ELE SYS

ENGINE FROM VEHICLE ENG VE

POWER SUPPLY P SUPP

COOLING SYSTEM COOL SYS

KEEP OUT OF THE REACH OF CHILDREN.

IT IS ADVISABLE TO WEAR LATEX GLOVES WHEN SERVICING THE VEHICLE.

THE BATTERY ELECTROLYTE IS TOXIC, CORROSIVE AND, AS IT CONTAINS SULPHURIC

GENERAL PRECAUTIONS AND INFORMATION

BEFORE DISASSEMBLING COMPONENTS

THE MODIFICATION OF THE IDENTIFICATION CODES IS A SERIOUS PUNISHABLE CRIME.

Dimensions and mass

ELECTRICAL SYSTEM SX 125 RX 125

Frame and suspensions

Wheels and tyres

HANDLEBAR AND CONTROLS

LIGHTS / INSTRUMENT PANEL

Recommended products chart

SPECIAL TOOLS S-TOOLS

AP0277875 Buffer for fitting oil seal 230425

AP0276502 Buffer for fitting oil seal 930675

AP0276770 Buffer for fitting oil seal 230195

AP0277970 Guide bushing for oil seal 930675

AP0876973 Piston ring clamp 54 mm

Stores code Description

AP0277180 Bearing tie rod kit

AP0277455 Extractor plate to separate the crankcase

AP0276380 bolt M10

AP0276370 Split bushing

AP0242091 Hexagon nut M10

Stores code Description

AP0242700 Flanged nut M8

AP0277445 Guillotine extractor

AP0977490 Ring for half-rings

AP0876298 Extractor for crankshaft bearings

Stores code Description

AP8146486 Front service stand

AP8140192 Chain fitting kit

AP8140180 Extractor for bushings

AP8705021 Rear service stand

AP8140204 Supports for rear service stand

AP8140199 Tool panel

Stores code Description

SX RX 125 ROUTINE MAINTENANCE TABLE

• Take out the spark plug tube.

FAILURE TO FOLLOW THESE OPERATIONS MAY RESULT IN AN INCORRECT READING OF

• Unscrew and remove the filler plug (2).

PARK THE MOTORCYCLE ON SAFE AND LEVEL GROUND.

• Screw the filler plug (1).

• Remove the right side central fairing.

• Remove the filtering element together

THE FILTERING ELEMENT MUST BE WELL IMPREGNA-

Check and top-up

DO NOT ADD ADDITIVES OR OTHER SUBSTANCES TO