SERVICE MANUAL

S6-C COMPETITION
50cc – 2 stroke - liquid cooled
 ENGINE
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INDEX

TECHNICAL SPECIFICATIONS 2

SPECIAL TOOLS 3-4

PERIODIC MAINTENANCE 5

LUBRICANTS 6

TROUBLESHOOTING 7 - 14

TIGHTENING TORQUE TABLE 15

ENGINE DISASSEMBLY 16 - 24

ENGINE REASSEMBLY 25 - 37

SPECIAL 3-SHOE CLUTCH DISASSEMBLY/REASSEMBLY 38 - 39

SPECIAL 3-SHOE CLUTCH ADJUSTMENT PROCEDURE 40

ENGINE COMPONENT INSPECTION AND SERVICE 41 - 43

GENERAL PARTS LIST + EXPLODED VIEW TABLES xx

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TECNICAL SPECIFICATIONS

SPECIFICATIONS
CYCLE ......................................................... - 2 stroke
Nr. of CYLINDERS ....................................... -1
DISPLACEMENT.......................................... - 49.908 cc.
BORE AND STROKE mm. ............ - 39 X 41.8
CYLINDER MATERIAL ................................. - Aluminium with Ni / Si carbide coating
COMPRESSION RATIO ................................ - (15.5 ±0.3) : 1
SPARK PLUG .............................................. - CHAMPION C53
TIMING SYSTEM .......................................... - Reed valve with 4 carbon fibre flaps
MAX. R.P.M. .................................................. - 14500 (rpm) MAX
CARBURETOR ............................................ - 12/14/19 mm diameter
INTAKE MANIFOLD ..................................... - Adjustable
FUEL ............................................................ - EURO UNLEADED NC 623/02 - R.O.N. 95
LUBRICATION OIL MIXER TYPE ................. - 2% AGIP 2T CITY
LUBRICATION WITH OIL PUMP .................. - On request
IGNITION ...................................................... - Electronic with microchip
PRIMARY DRIVE GEAR ............................... - Straight-tooth gears Z 14/59
..................................................................... with safety coupling
..................................................................... Ratio 1:4,21
SECONDARY DRIVE GEAR ......................... - Sprocket Z 10 or Z11
..................................................................... Chain type 1/2 x 3/16 roller 7.75
CLUTCH ...................................................... - Automatic centrifugal clutch in oil bath
..................................................................... Adjustable
TRANSMISSION GEAR OIL ......................... - SAE 20 W quantity 250 cc
STARTER ...................................................... - Kick starter
COOLING ...................................................... - With liquid pump

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SPECIAL TOOLS

Figure Code Description

BEARING INSTALLER
143176 output shaft

BEARING INSTALLER
143154 crankshaft

143156 BEARING INSTALLER

output shaft

143179 OIL SEAL INSTALLER

output shaft

143180 OIL SEAL INSTALLER

crankshaft (flywheel + clutch)

143181 OIL SEAL MOUNTING PROTECTION

crankshaft (flywheel + clutch)

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SPECIAL TOOLS

Figure Code Description

OIL PUMP SHAFT INSTALLER

143155 (pre-assembled)

140558 FLYWHEEL REMOVER

143162 CRANKCASE PULLER

SPECIAL CLUTCH ADJUSTMENT TOOL

143294

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PERIODIC MAINTENANCE

RUNNING-IN RECOMMENDATIONS:

During the running-in period, i.e. for approx. the first 500 km on the road, please note as follows:
- Do never run the engine at maximum revolutions.
- Do never keep the vehicle at maximum speed.
- Do not keep the engine at idle speed for longer time.

FIRST MAINTENANCE SERVICE:

to be carried out after 500 - 600 km.

- Replace the engine oil

- Check the carburation and adjust if necessary
- Check the tightness of nuts and bolts.
(See table “tightening torques” pag. 15)

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LUBRICANTS

N.B.
Use original MORINI FRANCO MOTORI spare parts only

RECOMMENDED LUBRICANTS / ADHESIVES

DESCRIPTION CHARACTERISTICS

Transmission oil AGIP RADULA 68 SAE 20W

Assembly of various parts GR/SM2 GREASE

Special assembly GRAPHITISED MOLYCOTE type GREASE

Thread-locking glue LOXEAL 82-21

Clamping glue LOXEAL 83-54

N.B. TRANSMISSION OIL LEVEL CHECK

Remove the oil filler cap on the clutch cover and check the transmission oil level
through window.

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TROUBLESHOOTING

The following flow charts give a general outline of the causes and effects when the engine is not
running correctly.
Descriptions of solutions for a specific cause are general; for more details the reader should
consult the disassembly-reassembly manual.

LEGEND OF SYMBOLS

EFFECT (fault noticed by the user)

Possible CAUSE of the fault

Possible general SOLUTION to the fault

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Starting problems

Faulty spark plug YES Check spark plug and

or wrong spark plug replace if necessary.
heat rating

NO

Start the engine with the

YES throttle fully open.
Engine flooded

NO Remove the spark plug, NO

rev the engine, install a The engine
dry spark plug and restart starts
the engine.

Sparking starts at YES

Replace the ignition coil
high r.p.m.

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Maximum indicated running

speed cannot be reached

Disassemble, wash sponge with a

Soiled or 50% solution of petrol and 2T oil;
clogged YES leave to dry. Clean the filter box
filter
using compressed air; re-
assemble.

NO

Silencer YES Check the silencer for clogging.

obstructed Replace if necessary.

NO

Cylinder Disassemble the cylinder and check

exhaust port YES that the exhaust pipe is clean. If the
soiled with exhaust pipe is partly obstructed by
carbon carbon deposits, clean it thoroughly
deposits
using a scraper.

NO

Disassemble the cylinder head,

Poor
cylinder and piston.
compression
YES Remove the piston rings, place
them in the cylinder liner and check
the amount of wear.
Replace if excessively worn.

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Poor acceleration / pickup

Check the cluth shoe thickness and

Clutch
YES the clutch springs for stretching.
If excessively worn they should be
replaced.

NO

Check the exact number of turns

Irregular YES
acceleration of the air adjusting screw on the
carburetor.

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Incorrect idling speed

Adjust the RPM of the idling speed

Idling speed YES (with engine warm) by adjusting the
too high or
too low
screw on the throttle valve of the
carburetor.

Disassemble the carburetor and

clean all parts (nozzles, throttle val-
YES
ve, jet needle, float chamber and
NO body) with solvent and dry by using
compressed air.

False air
intake from YES Check the integrity of the
carburetor carburetor manifold gaskets.
manifold

Check the integrity of the rubber

YES coupling sleeve that connects the
NO carburetor and air filter box .

YES Check the reed valve gasket.

False air
intake YES Check the integrity of the
from engine crankshaft oil seals. Replace
crankshaft even if only slightly damaged.
oil seals

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Noisy engine

Incorrect Check the assembly of all gears and

transmission YES parts of the transmission.
gears
assembly

NO

Loose Check the tightening torque of the

transmission
YES
clutch nut.
nut

NO

Transmission
noise and rear YES
Check the clutch unit
wheel drag at
idling speed.

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Noisy engine

Check the oil level.

YES Refill if necessary.
Noisy gears

Check the teeth of the drive gears

YES visually.
Replace if signs of damage or
wear are evident.
NO

Check the clearance between the

Noisy piston and the cylinder. If it does
cylinder YES
unit
not correspond to the prescribed
value, replace the cylinder and
piston.

NO

BEARING INSPECTION
Rotate the bearing inner race by fin-
Noisy ger to inspect for abnormal play, noise
crankshaft YES
and smooth rotation while the
bearings
bearings are mounted in the
crankcase.
Replace the bearing if anything
unusual is found.

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Smokey exhaust

Percentage of YES Replace the fuel in the tank with

mixer oil new fuel mixed with 2% of the type
of oil indicated in the handbook.

NO

Mixer oil
YES Check that the oil is 100%
synthetic for separate oil mixer
pump use.

NO

Disassemble the cylinder and

Carbon YES remove any carbon deposits;
deposits check the silencer for clogging.

NO

Oil mixer YES Disassemble the oil mixer pump

pump and check the flow rate.

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TIGHTENING TORQUES

TORQUE
DENOMINATION
(Nm)
Cranckcase bolts 10 - 12
Clutch cover bolts 10 - 12
Flywheel cover bolts 3-4
Carburetor manifold bolts 9 -10
Stator clamping bolts 3-4
Oil pump clamping bolts 5-6
Carburetor clamping screw 3-4
Kick starter lever bolt 8 - 10
Oil drain plug 8 - 10
50 - 55
Clutch nut
+ Loxeal 83-54
8 -10
Flywheel nut
+ Loxeal 83-54
Head nuts 12 - 14
Head clamping bolts 10 - 12
3-4
Pulley clamping bolts
+ Loxeal 83-54
5-6
Water pump rotor + Loxeal 83-54

Spark plug 20 - 25

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ENGINE DISASSEMBLY

CARBURETOR UNIT

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Disassemble the CARBURETOR

BEFORE LOOSEN
THE SCREWS
CHECK ACTUAL
MANIFOLD ANGLE
Loosen the SCREWS and remove the POSITION
CARBURETOR MANIFOLD
THE MANIFOLD IS
COMPOSED BY 4
ELEMENTS.

Remove the CARBURETOR

MANIFOLD BASE including the
REED VALVE

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CYLINDER HEAD - CYLINDER - PISTON

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Remove the SPARK PLUG

Remove the 4 CYLINDER HEAD

BOLTS

Remove the 4 CYLINDER HEAD

NUTS

Remove the CYLINDER HEAD PAY ATTENTION TO

THE DOWEL PINS

Check the condition of the O-RING

(HEAD GASKET).
Replace if excessively worn.

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TOOL
DIAGRAM DESCRIPTION CODE NOTES

Disassemble the CYLINDER and

remove the CYLINDER BASE
GASKET

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FLYWHEEL SIDE

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Loosen the clamping BOLTS and MIND THE BRACKET

remove the FLYWHEEL COVER INSIDE THE COVER

Disassemble the FLYWHEEL

STATOR

ROTOR LOCK NUT

Disassemble the FLYWHEEL 143151 CLAMPED WITH
ROTOR LOXEAL

Remove the PULLEY CLAMPING

BOLT

Remove the DRIVEN PULLEY

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TOOL
DIAGRAM DESCRIPTION CODE NOTES

Remove the PUMP DRIVE BELT

Remove the SPECIAL SNAP RING

Remove the SPACER RING

The following operations can only be carried out after opening the crankcase

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Unscrew the WATER PUMP ROTOR

BLOCK THE PUMP
SHAFT

Remove the PUMP SHAFT UNIT

including the bearings.
The pump shaft seal ring must be PAY ATTENTION
replaced by every disassembly. TO THE SPACERS
The 2 bearing snap rings on the BETWEEN THE
water pump must be replaced by BEARINGS
every disassembly.

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CLUTCH SIDE

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Disassemble the CLUTCH ONLY IF CLUTCH

ADJUSTING PLUG NEEDS TO BE
ADJUSTED

MAKE SURE TO
Remove the OIL DRAIN PLUG DRAIN THE
(cross head) ENGINE
COMPLETELY

Loosen the clamping BOLTS on the

cover and remove the CLUTCH
COVER

Remove the SPECIAL FRONT Compass tool CLAMPED WITH

CLUTCH NUT and the LOXEAL.
BELLEVILLE WASHER

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TOOL
DIAGRAM DESCRIPTION CODE NOTES

Disassemble the SPECIAL CLUTCH

and the 2.5mm SPACER RING

Remove the CLUTCH BELL and the

0.8mm SPACER RING

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CRANKCASE “OPENING”

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Remove the cylinder STUD BOLTS if

necessary BLOCKED WITH
LOXEAL

Remove the 8 CRANKCASE BOLTS

THE CRANKSHAFT
IS DRIVEN ONTO
THE BEARINGS.
Open the CRANKCASE 143162 OPEN THE
CRANKCASE FROM
FLYWHEEL SIDE
USING THE
PULLER TOOL

Remove the DOWEL PINS and the

CRANKCASE GASKET.
Remove the crankshaft if necessary

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TOOL
DIAGRAM DESCRIPTION CODE NOTES

Remove the OUTPUT SHAFT SNAP

RING

Remove the OUTPUT SHAFT

Inspect the OUTPUT SHAFT

BEARING for abnormal play and noise.
Replace the bearing if anything
unusual occurs.

Remove the SNAP RING

Remove the BEARING by using a

standard bearing remover set.
THE BEARING IS
DRIVEN INTO THE
BEARING HOUSING

To replace the CRANKSHAFT

BEARING and the OUTPUT SHAFT
ROLLER CAGE (flywheel side) follow
the same procedure as described
above.

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ENGINE REASSEMBLY

WATER PUMP PREASSEMBLY

TOOL
DIAGRAM DESCRIPTION CODE NOTES
Preassemble the WATER PUMP
SHAFT UNIT by mounting the
components in the following order:
snap ring + bearing + spacer + bearing
and secure with the snap ring.

Insert the complete unit in the HALF

CRANKCASE FLYWHEEL SIDE

Insert the SPACER RING

Insert the SPECIAL SNAP RING

THE SEAL RING

Insert the SEAL RING 143155 MUST ALWAYS BE
REPLACED WITH A
NEW ONE

Reassemble the Tightening torque

WATER PUMP ROTOR 5 - 6 Nm +
Loxeal 83 - 54

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CRANKCASE PREASSEMBLY

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Drive the OUTPUT SHAFT BEARING LUBRICATE THE

143176 HOUSING
into the half crankcase clutch side and
secure with the snap ring
LEAVE THE PRINT
ON THE BEARING
VISIBLE

LUBRICATE THE
HOUSING
Drive the CRANKSHAFT BEARINGS
into the half crankcase clutch side and 143154 LEAVE THE PRINT
into the half crankcase flywheel side. ON THE BEARING
VISIBLE

LUBRICATE THE
HOUSING

Drive the ROLLER CAGE OUTPUT 143156 LEAVE THE PRINT

SHAFT into the half crankcase ON THE BEARING
flywheel side. VISIBLE

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TOOL
DIAGRAM DESCRIPTION CODE NOTES

Insert the DRIVE SHAFT in the half

crankcase clucth side

Insert the SNAP RING onto the

second output shaft slot (near
transmission gear)

Insert the OUTPUT SHAFT into the half

crankcase clutch side and secure with
SNAP RING

CRANKCASE “CLOSING”

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Insert the DOWEL PINS

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TOOL
DIAGRAM DESCRIPTION CODE NOTES

Lubricate the CRANKCASE GASKET

on both sides.

Apply the CRANKCASE GASKET on

the half crankcase clutch side using
the 2 dowel pins for centering.

Assembly the HALF CRANKCASES

Fix 1 x BOLT M6X60 in the postion DO NOT TIGHTEN

between the stud bolts and the reed
valve zone.

Fix the remaining 7 X BOLTS M6X50.

Cross-tighten the bolts using a
tightening torque of 10-12 Nm.
Check to make sure that the
crankshaft and output shaft rotate
smootly.

Grease the oil seal housing and the GREASE TYPE

oil seal lip carefully. GR/SM2
143179
Install the CRANKSHAFT OIL SEAL 143180
RINGS and the OUTPUT SHAFT OIL 143181
SEAL RING.

Trim the crankcase gasket (cylinder

zone and carburetor zone.)

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FLYWHEEL SIDE

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Mount the DRIVEN PULLEY on the

water pump shaft and position the
PUMP DRIVE BELT on the splined
section of the crankshaft.

Tightening torque
3 - 4 Nm +
Secure the pulley with bolt M4x14
Loxeal 83- 54

Mount the SPROCKET and secure

with the SNAP RING

Place the UNDER ROTOR SPACER

on the crankshaft.

Caulk the key seat on the crankshaft

and insert the FLYWHEEL KEY.

Mount the FLYWHEEL ROTOR with the 143151 Tightening torque

black side facing the crankcase. 8 - 10 Nm +
Loxeal 83 - 54

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TOOL
DIAGRAM DESCRIPTION CODE NOTES

Install the FLYWHEEL STATOR with

the output cable facing the crankcase.

Tightening torque
Secure the flywheel stator with 3 - 4 Nm
2 BOLTS M4 x 18

Drive in the 2 elastic dowel pins in the

cover. and make sure that they do
NOT INTERFERE with the bracket
mounting face.

Assemble the BRACKET on the

flywheel cover.

Assemble the FLYWHEEL COVER

placing the rubber fairleads in their
proper seats on the cover.

Secure the FLYWHEEL COVER using:

3 SCREWS M5X50 + WASHER. Tightening torque

1 SCREW M5X20 + WASHER. 3-4 N.m.

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CYLINDER - PISTON - HEAD UNIT

TOOL
DIAGRAM DESCRIPTION CODE NOTES

WHEN
INSTALLING THE
Assemble the ROLLER CAGE, PISTON TURN
PISTON and PISTON PIN and THE ARROW
secure with CIRCLIPS. MARK ON THE
HEAD OF THE
OIL THE PISTON PISTON TO THE
EXHAUST SIDE

Insert the CYLINDER BASE GASKET

and mount the CYLINDER

Insert the CYLINDER HEAD DOWEL

PINS

Apply the O-RING SEAL on the

CYLINDER HEAD

Install the CYLINDER HEAD on the

CYLINDER using the dowel pins as
centering reference

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TOOL
DIAGRAM DESCRIPTION CODE NOTES

Fit the 4 CYLINDER HEAD NUTS on (Cross tighten)

the stud bolts and tighten Tightening torque
12 - 14 Nm.

(Cross tighten)
Fit the 4 CYLINDER HEAD BOLTS and Tightening torque
tighten 10 - 12 Nm.

Install the SPARK PLUG and tighten Tightening torque

20 - 25 Nm.

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CARBURETOR UNIT

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Insert the CARBURETOR MANIFOLD

BASE including the REED VALVE.

Check the angle

position of the
Assemble the CARBURETOR MANIFOLD before
MANIFOLD on the base and secure tightening the
with 4 BOLTS M6X25. bolts.

Tightening torque
9 - 10 Nm.

Tightening torque
Assemble the CARBURETOR and 3 - 4 Nm.
tighten the CLAMP SCREW.

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CLUTCH COVER

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Drive the WATER CIRCUIT DELIVERY

PIPE into place

Assemble the SPRING on the sliding

gear as shown on the figure.
143167
Lubricate the inside of the spring using
GR MU/3 grease.

Assemble the SLIDING GEAR on

the cover and secure the SPRING
between the two stops.

Assemble the SPACER RING and

O-RING on the KICK STARTER
SHAFT.

Lubricate the O-ring area using

GR MU/3 grease.

Lubricate the KICK STARTER

SHAFT in the clutch cover operating
zone using grease type MOLYCOTE.
Install KICK STARTER SHAFT in the
clutch cover and make sure that the
gear section is engaged properly with
the sliding gear.
After assembly check that the spring
of the sliding gear is correctly
positioned between the two stops.

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TOOL
DIAGRAM DESCRIPTION CODE NOTES

Install and load the RETURN SPRING

on the kick starter shaft.

Secure the spring on the backstop in

the clutch cover.

Assemble the SPRING WASHER and

secure with the SNAP RING.

Place the SPACER on the kick starter

shaft and secure with the snap ring.

Assemble the KICK STARTER LEVER Tightening torque

and fasten by using the bolt M7x25. 8-10 N.m.

KICK STARTER LEVER POSITION

*Steel lever = 109°
*Aluminium lever = 96°

Check axial clearance: 0.1 - 0.3 mm

KICK STARTER LEVER POSITION

*Steel lever = 109° *Aluminium lever = 96°

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CLUTCH SIDE

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Insert the 0.8mm SPACER RING on

the crankshaft clutch side.

Lubricate the clutch bell operating zone

of the crankshaft using the grease type
ROCOL ASP MOLYCOTE.

Install the CLUTCH BELL

Insert the 2.5 mm SPACER RING

Install the CLUTCH ON THE

CRANKSHAFT, INSERT THE CAUTION
BELLEVILLE WASHER and clamp
the clutch using the SPECIAL In order to avoid
FRONT-CLUTCH NUT. any clutch hub
(LEFT HAND THREAD) jamming on the
spline shaft and to
Add LOXEAL 83-54 to the clutch nut Compass tool ensure any future
and tighten disassembly
operation of the
Tightening torque 50-55 N.m. clutch unit, make
sure to apply
Check the axial clearance of the LOXEAL 83-54
clutch bell: 0.3 - 0.5 mm exclusively on the
cluth nut and NOT
Assemble the clutch cover gasket. on shaft end.

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TOOL
DIAGRAM DESCRIPTION CODE NOTES

Mount the clutch cover and secure Tightening torque

with 6 BOLTS M6 x 30. 10-12 N.m.

Insert the OIL DRAIN PLUG + Tightening torque

WASHER and tighten. 8-10 N.m.

Recommended
Pour 250 cc of oil type AGIP
Oil type:
RADULA 68 SAE 20W and fit the
OIL FILLER CAP + GASKET.
AGIP RADULA 68
SAE 20W
AFTER COMPLETED ASSEMBLY
CHECK THAT THE ENGINE
ROTATES SMOOTHLY

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S6 OIL MIXER PUMP

TOOL
DIAGRAM DESCRIPTION CODE NOTES

Preassemble the 2 BEARINGS and

SPACER on the OIL MIXER PUMP
DRIVE SHAFT and secure with 2
SNAP RINGS.

The print on the bearings should face

the drive end of the shaft.

Lubricate the bearing housing.

Drive the OIL MIXER PUMP DRIVE 143155
SHAFT UNIT into the half crankcase
flywheel side.

Insert the CLEARANCE SPACER.

Assemble the BEARING SNAP 143342
RING.

Insert the DRIVE BELT onto the

DRIVEN PULLEY.

Install the pulley on the oil mixer pump

shaft and the drive belt onto the splined
part of the crankshaft.

Assemble the oil mixer pump on the Tightening torque

support bracket and tighten the 5 - 6 Nm
screw M5x12.

In order to simplify the assembly

operation of the oil mixer pump,
make sure that the timing of the
driven pulley and the oil mixer
pump shaft do match.

Install the BRACKET with OIL

MIXER PUMP into the housing of the
half crankcase flywheel side.

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SPECIAL 3-SHOE CLUTCH

DISASSEMBLY

Remove the 3 special clutch adjusting screws.

ATTENTION
Each screw contains 1 spring an 2 balls.

Remove the 21 Belleville washers.

Take note of the assembly configuration.

Remove the screw couplings.

Unscrew the clutch shoe retainer pawls and

remove the flat spring.

Disassemble the clutch shoes, the bushings

and the 3 clutch shoe socket screws M4x14.

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SPECIAL 3-SHOE CLUTCH REASSEMBLY

Grassare = Lubricate

Apply a thin film of molycote grease on the shoe-holder plate.

Insert the clutch shoe socket screws.

Lubricate the outer diameter working zone of the 3 bushings with

molycote grease.
Insert the bushings in the clutch shoe fulcrums.

Position and install the clutch shoes on the shoe-holder plate using
the bushings as centering references.
Apply a thin film of molycote grease on the working area of the flat
spring.

Assemble the flat spring on the clutch with the 3 clutch shoe
retainer pawls and tighten.

Tightening torque 5.8 - 6.8 Nm

Lubricate the square holes in the flat spring and insert the 3 screw
coupling.

Grassare = Lubricate

Insert 7 Belleville washers in each hole

maintaining the correct assembly configuration.
See figure.

Sede molle = Spring seat.

Place 2 balls and 1 spring in each of the 3 special clutch

adjusting screws.

Install the 3 adjusting screws making sure that the balls and the
the springs remain positioned correctly in the screw housings.

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SPECIAL 3-SHOE CLUTCH ADJUSTMENT PROCEDURE

Screw knob “C”

Clutch shoe stop

Check pin “A”

Clearance “X” = 0.25 mm

Place the clutch on the special tool code 143294 and block it using the screw knob “C”.
Position the clutch with one of the shoes blocked against the tool clutch shoe stop.
Mount the main tool screw knob “C” and apply a constant torque of 8,5 Nm by using a
dynamometric spanner tool with direct torque reading.

When keeping the torque constant, check the clearance “X” between the shoe and the check
pin “A” using a thickness gauge.

CAUTION
The thickness gauge must make minimal friction against the parts: it should not pass freely
and should not stick between the clutch shoe and the check pin.

Make sure that the thickness gauge do pass along the entire thickness “Y” of the shoes.

ADJUSTMENT PROCEDURE (1 clutch shoe at a time)

1/Unload the dynamometric spanner tool.
2/To increase the clearance “X” turn the screw “B” clockwise.
3/To decrease the clearance “X” turn the screw “B” aniti clockwise.
4/Repeat the procedure for each clutch shoe.

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ENGINE COMPONENT INSPECTION AND SERVICE

CYLINDER - PISTON TABLE

Value (mm)
Part
50cc
Cylinder Ø 39
Piston Ø 39
Piston rings :
1)Piston ring 1st slot Ø 39 x 2 - 0.01 - 0.025
2)Piston ring 2nd slot Ø 39 x 1.25 - 0.01 - 0.025

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CYLINDER - PISTON
ASSEMBLY SELECTION TABLE

CYLINDER - PISTON
DIMENSIONS mm ASSEMBLY
SIZE CODE
(stamped on part) CLEARANCE
CYLINDER PISTON

+ 0,010
A ø 39 +0,005 ø 39 - 0,025
- 0,030

+ 0,015 - 0,020
B ø 39 + 0,010 ø 39
- 0,025

+ 0,020 - 0,015 0.030 - 0.040

C ø 39 + 0,015 ø 39 - 0,020 mm
+ 0,025 - 0,010
D ø 39 + 0,020 ø 39 - 0,015

+ 0,030 - 0,005
E ø 39 + 0,025 ø 39 - 0,010

+ 0,035 -0
F ø 39 + 0,030 ø 39 - 0,005

CHECK POSITION
For correct dimension control

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CYLINDER CHECK
-Check the internal surface of the cylinder for
signs of seizure or abnormal wear.
-Measure the internal diameter of the cylinder
using a bore gauge.
-Wear limit: Minimum indicated cylinder
selection diameter + 0.03mm.
-Take measurements in three different positions
along the axis of the cylinder.
-In each position take two measurements, one
parallel with and the other perpendicular to the
crankshaft axis.

PISTON CHECK

-Remove the piston rings and check the piston

for abnormal signs and wear.

N.B.
The piston rings are fragile, handle with care.

RING-TO-GROOVE MEASUREMENT.
Wear limit: 0,08 mm max.

PISTON BORE MEASUREMENT.

-Maximum permitted diameter:12 + 0,18 mm
+0,18
-Measure the piston outside diameter in the
direction perpendicular to the piston axis at
14,5 mm from the skirt.

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