SYM Jet Euro User Manual

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SERVICE MANUAL

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This service manual contains the technical data of each component inspection
and repair for the SANYANG JET 50/100 and JET Euro 50/100 series
motorcycle. The manual is shown with illustrations and focused on “Service
Procedures”, “Operation Key Points”, and “Inspection Adjustment” so that
provides technician with service guidelines.

If the style and construction of the motorcycle, JET 50/100 and JET Euro
50/100 series, are different from that of the photos, pictures shown in this
manual, the actual vehicle shall prevail. Specifications are subject to change
without notice.

Service Department

Sanyang Industry Co., LTD.

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Contents

How to Use This Manual

This service manual describes basic information of different system parts and
system inspection & service for Sanyang JET 50/100 and JET Euro 50/100
series motorcycles. In addition, please refer to the manual contents in detailed
for the model you serviced in inspection and adjustment.

The first chapter covers general information and trouble diagnosis.
The second chapter covers service maintenance information.
Th third to the tenth nine chapters covers engine and driving systems.
The tenth to the fourteenth is contained the parts set of assembly body.
The fifteenth chapter is electrical equipment.
The sixteenth chapter is wiring diagram

Please see index of content for quick
having the special parts and system
information.

All information, illustration, directions and specifications included in this manual
are current as at the time of publication. Sanyang reserves the rights to make
changes at any time without prior notice and without incurring any obligation
whatever. Without written consent by SANYANG can not copy any part of this
manual.

There are 4 buttons, “Forward,” “How to use this manual,” “Mechanism

Illustrations,” and “Contents” on the CD-R version, and can be access to

these items by click the mouse.
If user wants to look for the content of each chapter, selecting the words of
each chapter on the main contents can reach to each chapter. There are
two buttons, Back to homepage and Main contents, onto the top line of first
page of the each chapter. Thus, if the user needs to check other chapters, he
can click the top buttons to back the homepage or main contents. The
content of each chapter can be selected too. Therefore, when needs to
checking the content inside of the chapter, click the content words of the
chapter so that can back to the initial section of the content. In addition,
there is a “This chapter contents” button at the top line of each page so that
clicking the button can back to the contents of this chapter.

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CONTENTS

Page Content Index

1-1 ~ 1-18

2-1 ~ 2-14

3-1 ~ 3-6

4-1 ~ 4-4

5-1 ~ 5-8

6-1 ~ 6-4

GENERAL INFORMATION

SERVICE MAINTENANCE INFORMATION

LUBRICATION SYSTEM

ENGINE REMOVAL

CYLINDER HEAD/CYLINDER/PISTON

ALTERNATOR

1

2

3

4

5

6

7-1 ~ 7-14

8-1 ~ 8-6

9-1 ~ 9-6

10-1 ~ 10-10

11-1 ~ 11-12

12-1 ~ 12-12

13-1 ~ 13-10

14-1 ~ 14-4

“V” TYPE BELT DRIVING SYSTEM/KICK-STARTER

FINAL DRIVING MECHANISM

CRANKCASE/CRANKSHAFT

FUEL SYSTEM

BRAKE SYSTEM

BODY COVER

STEERING/FRONT WHEEL/SUSPENSION

REAR WHEEL/SUSPENSION

7

8

9

10

11

12

13

14

15-1 ~ 15-22

ELECTRICAL EQUIPMENT

15

16-1 ~ 16-4

ELECTRICAL DIAGRAM

16

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Contents

MODEL ILLUSTRATION

JET 50 / 100 Series

Front turn signal

Light / Starter switch

Fuel tank cap

Rear turn signal

Seat lock

Rear turn signal

Helmet hook

High & Low beam /
Turn signal / Horn switch

Battery / Fuses / C.D.I. /
Eng. Oil tank cap

Frame number

Head light

Front brake lever Rear brake lever

Tail light

Storage box

Air cleaner

Ignition switch

Engine number

Muffler

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Contents

JET Euro Series

Front turn signal

MODEL ILLUSTRATION

Light / Starter switch

Fuel tank cap

Rear turn signal

Seat lock

Rear turn signal

Helmet hook

High & Low beam /
Turn signal / Horn switch

Battery / Fuses / C.D.I. /
Eng. Oil tank cap

Frame number

Head light

Front brake lever

Tail light

Storage box

Air cleaner

Ignition switch

Rear brake lever

Engine number

Muffler

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Contents

1. GENERAL INFORMATION

Symbols and Marks···························1-1
General Safety···································1-2
Service Precautions··························1-3
Specifications····································1-5

Torque values·································· 1-7
Cables and Harness Routing·········· 1-9
Troubleshooting······························ 1-13
Lubrication Points··························· 1-17

Symbols and Marks

Symbols and marks are used in this manual to indicate what and where the special service are
needed, in case supplemental information is procedures needed for these symbols and marks,
explanations will be added to the text instead of using the symbols or marks.

Warning

Caution

Engine oil

Means that serious injury or even death may result if procedures are not
followed.

Means that equipment damages may result if procedures are not
followed.

Limits to use SAE 20 JASO FC class oil. Warranty will not cover the
damage that caused by not apply with the limited engine oil.
(Recommended oil: MAX-2 serial oils)

1

O

X

Grease

Gear oil
Locking

sealant
Oil seal

Renew

Brake fluid

Special tools

Correct

Wrong

Indication

Directions

King Mate G-3 is recommended.

King Mate gear oil serials are recommended. (Bramax HYPOID GEAR
OIL # 140)

Apply sealant, medium strength sealant should be used unless
otherwise specified.

Apply with lubricant.

Replace with a new part before installation.

Use recommended brake fluid DOT3 or WELLRUN brake fluid.

Special tools.

Meaning correct installation.

Meaning wrong installation.

Indication of components.

Indicates position and operation directions.

Components assembly directions each other.
Indicates where the bolt installation direction, --- means that bolt cross

through the component (invisibility).

1-1

This chapter Contents

1. GENERAL INFORMATION

General Safety

Carbon monoxide

If you must run your engine, ensure the place is
well ventilated. Never run your engine in a
closed area. Run your engine in an open area, if
you have to run your engine in a closed area, be
sure to use an extractor.

Caution

Exhaust contains toxic gas which may cause
one to lose consciousness and even result in
death.

Gasoline

Gasoline is a low ignition point and explosive
material. Work in a well-ventilated place, no
flame or spark should be allowed in the work
place or where gasoline is being stored.

Caution

Gasoline is highly flammable, and may
explode under some conditions, keep it away
from children.

Used engine oil

Caution

Prolonged contact with used engine oil (or
transmission oil) may cause skin cancer
although it might not be verified.

We recommend that you wash your hands
with soap and water right after contacting.
Keep the used oil beyond reach of children.

Hot components

Caution

Components of the engine and exhaust
system can become extremely hot after
engine running. They remain very hot even
after the engine has been stopped for some
time. When performing service work on these
parts, wear insulated gloves and wait until
cooling off.

Battery

Caution

y Battery emits explosive gases; flame is

strictly prohibited. Keep the place well
ventilated when charging the battery.

y Battery contains sulfuric acid (electrolyte)

which can cause serious burns so be
careful do not be spray on your eyes or
skin. If you get battery acid on your skin,
flush it off immediately with water. If you get
battery acid in your eyes, flush it off
immediately with water and then go to
hospital to see an ophthalmologist.

y If you swallow it by mistake, drink a lot of

water or milk, and take some laxative such
as castor oil or vegetable oil and then go to
see a doctor.

y Keep electrolyte beyond reach of children.

Brake shoe

Do not use an air hose or a dry brush to clean
components of the brake system, use a vacuum
cleaner or the equivalent to avoid dust flying.

Caution

Inhaling dust may cause disorders and cancer
of the breathing system.

Brake fluid

Caution

Spilling brake fluid on painted, plastic, or
rubber parts may cause damage to the parts.
Place a clean towel on the above-mentioned
parts for protection when servicing the brake
system. Keep the brake fluid beyond reach of
children.

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This chapter Contents

1. GENERAL INFORMATION

Service Precautions

z Always use with Sanyang genuine parts and

recommended oils. Using non-designed parts
for Sanyang motorcycle may damage the
motorcycle.

z Special tools are designed for remove and

install of components without damaging the
parts being worked on. Using wrong tools may
result in parts damaged.

z When servicing this motorcycle, use only

metric tools. Metric bolts, nuts, and screws are
not interchangeable with the English system,
using wrong tools and fasteners may damage
this vehicle.

z Clean the outside of the parts or the cover

before removing it from the motorcycle.
Otherwise, dirt and deposit accumulated on the
part's surface may fall into the engine, chassis,
or brake system to cause a damage.

z Rubber parts may become deteriorated when

old, and prone to be damaged by solvent and
oil. Check these parts before installation to
make sure that they are in good condition,
replace if necessary.

z When loosening a component which has

different sized fasteners, operate with a
diagonal pattern and work from inside out.
Loosen the small fasteners first. If the bigger
ones are loosen first, small fasteners may
receive too much stress.

z Store complex components such as

transmission parts in the proper assemble
order and tie them together with a wire for ease
of installation later.

z Wash and clean parts with high ignition point

solvent, and blow dry with compressed air. Pay
special attention to O-rings or oil seals because
most cleaning agents have an adverse effect
on them.

z Never bend or twist a control cable to prevent

stiff control and premature worn out.

z Note the reassemble position of the important

components before disassembling them to
ensure they will be reassembled in correct
dimensions (depth, distance or position).

z Components not to be reused should be

replaced when disassembled including gaskets
metal seal rings, O-rings, oil seals, snap rings,
and split pins.

Caution

In addition to damaging paint finish, brake oil
can also damage the structural integration of
plastic or rubber parts.

1-3

This chapter Contents

1. GENERAL INFORMATION

z The length of bolts and screws for assemblies,

cover plates or boxes is different from one
another, be sure they are correctly installed. In
case of confusion, Insert the bolt into the hole
to compare its length with other bolts, if its
length out side the hole is the same with other
bolts, it is a correct bolt. Bolts for the same
assembly should have the same length.

z Tighten assemblies with different dimension

fasteners as follows: Tighten all the fasteners
with fingers, then tighten the big ones with
special tool first diagonally from inside toward
outside, important components should be
tightened 2 to 3 times with appropriate
increments to avoid warp unless otherwise
indicated. Bolts and fasteners should be kept
clean and dry. Do not apply oil to the threads.

z When oil seal is installed, fill the groove with

grease, install the oil seal with the name of the
manufacturer facing outside, check the shaft on
which the oil seal is to be installed for
smoothness and for burrs that may damage the
oil seal.

z The ends of rubber hoses (for fuel, vacuum, or

coolant) should be pushed as far as they can
go to their connections so that there is enough
room below the enlarged ends for tightening
the clamps.

z Rubber and plastic boots should be properly

reinstalled to the original correct positions as
designed.

Boots

z The tool should be pressed against two (inner

and outer) bearing races when removing a ball
bearing. Damage may result if the tool is
pressed against only one race (either inner
race or outer race). In this case, the bearing
should be replaced. To avoid damaging the
bearing, use equal force on both races.

Manufacturer's name

z Remove residues of the old gasket or sealant

before reinstallation, grind with a grindstone if
the contact surface has any damage.

1-4

Both of these examples can result in bearing damage.

z Lubricate the rotation face as assembling.

Check if positions and operation for installed
parts is in correct and properly.

g

This chapter Contents

1. GENERAL INFORMATION

Specifications

Make SANYANG MODEL JET 50 SERIES

Overall Length 1785 mm Front TELESCOPIC

Overall Width 630 mm

Overall Height 1115 mm Front 120 / 70 – 12

DIMENSION

Wheel Base 1275 mm

Front 40 kg

ht

Curb

Passengers /

WEIGHT

Total Weight

Rear 54 kg

Wei

Total 94 kg

Weight

Front 84 kg Climb Ability 22° Below

Rear 120 kg Primary Reduction BELT

Total 204 kg

Suspension

System

Tire

Specifications

Brake System

Two /110 kg Max. Speed 50 km/hr Below

Secondary

Reduction

Rear UNlT SWING

Rear 130 / 70 – 12

Front

Rear

DlSK (ψ190mm)

DRUM (ψ110mm)

GEAR

Type Gasoline Clutch Centrifugal, dry type

Installation and

arrangement

Fuel Used Unleaded (92/95) Speedometer 0 ~ 90 km/hr

Cycle/Cooling

Bore 39 mm Muffler Expansion & Pulse Type

Stroke 41.4 mm

Cylinder

Number/Arran

ENGINE

gement

Displacement 49.4 cc Solid Particulate

Compression

Ratio

Max. HP 3.2 kw / 7000 rpm

Max. Torque 4.6 Nm / 6500 rpm E.E.C. Below 2g / test

Ignition C.D.I. P.C.V. X

Horizontal, below

center, incline

2-stroke/forced air

cooled

Single Cylinder Lubrication System Separated-lubrication

7.2 : 1 CO

FORMAN PERCE

Transmission C.V.T.

Horn 80 ~ 112 dB/A

Exhaust Pipe Position

and Direction

Exhaust

Concentration

HC

Right side, and Backward

8.0 g/km ↓

5.0 g/km ↓

Starting System Electrical & kick

Catalytic reaction

control system

○

1-5

g

This chapter Contents

1. GENERAL INFORMATION

Specifications

Make SANYANG MODEL JET 100 SERIES

Overall Length 1785 mm Front TELESCOPIC

Overall Width 630 mm

Overall Height 1115 mm Front 120 / 70 – 12

DIMENSION

Wheel Base 1275 mm

Front 40 kg

ht

Curb

Passengers /

WEIGHT

Total Weight

Installation and

arrangement

Rear 54 kg

Wei

Total 94 kg

Weight

Front 84.5 kg Climb Ability 22° Below

Rear 122.5 kg Primary Reduction BELT

Total 207 kg

Type Gasoline Clutch Centrifugal, dry type

Two /110 kg Max. Speed 50 km/hr Below

Horizontal, below

center, incline

Suspension

System

Tire

Specifications

Brake System

Secondary

Reduction

FORMAN PERCE

Transmission C.V.T.

Rear UNlT SWING

Rear 130 / 70 – 12

Front

Rear

DlSK (ψ190mm)

DRUM (ψ110mm)

GEAR

ENGINE

Fuel Used Unleaded (92/95) Speedometer 0 ~ 120 km/hr

Cycle/Cooling

Bore 51 mm Muffler Expansion & Pulse Type

Stroke 49.6 mm

Cylinder

Number/Arran

gement

Displacement 101.3 cc Solid Particulate

Compression

Ratio

Max. HP 7.0 ps / 6500 rpm

Max. Torque 0.89 kg-m / 5500 rpm E.E.C. Below 2g / test

Ignition C.D.I. P.C.V. X

Starting System Electrical & kick

2-stroke/forced air

cooled

Exhaust Pipe Position

Single Cylinder Lubrication System Separated-lubrication

6.3 : 1 CO

Exhaust

Catalytic reaction

Horn 80 ~ 90 dB/A

and Direction

Concentration

control system

HC

Right side, and Backward

7000 ppm ↓

4.5 % ↓

X

1-6

This chapter Contents

1. GENERAL INFORMATION

Torque values

Standard Torque Values for Reference

Type Torque value Type Torque value

5 mm Bolt, nut 0.45 - 0.6 kg-m 5 mm Bolt 0.35 - 0.5 kg-m
6 mm Bolt, nut 0.8 - 1.2 kg-m 6 mm Bolt, SH nut 0.7 - 1.1 kg-m
8 mm Bolt, nut 1.8 - 2.5 kg-m 6 mm Flange bolt, nut 1.0 - 1.4 kg-m
10 mm Bolt, nut 3.0 - 4.0 kg-m 8 mm Flange bolt, nut 2.4 - 3.0 kg-m
12 mm Bolt, nut 5.0 - 6.0 kg-m 10 mm Flange bolt, nut 3.5 - 4.5 kg-m

The torque values listed in below table are for more important tighten torque values. Please see
above standard values for not listed in the table.

Engine

Item Q’ty

Cylinder head bolt

4

Thread Dia.

(mm)

6

Torque Value

(Kg-m)

1.0

Remarks

When engine

cooled
Spark plug
Flywheel nut
Sliding driving disc nut
Sliding driving disc nut
Clutch outer cover nut
Drain bolts
Crankcase bolts

1 14 1.4
1 10 3.8
1 10 3.8
1 28 5.5
1 10 3.8
1 8 1.3
6 6 1.0

1-7

This chapter Contents

1. GENERAL INFORMATION

Frame

Item Q’ty

Bolt for engine suspension

Bolt for engine suspension bracket

Upper bolt for rear shock absorber

Lower bolt for rear shock absorber

Mounting screws for exhaust pipe
connection

Nut for exhaust

Brake hose bolts

Brake caliper mounting bolts

Brake cushion guide bolts

1

1

1

1

2

2

2

2

2

Thread Dia.

(mm)

10 5.0

12 6.0

10 4.0

8 2.7

6 1.2

8 3.3

10 3.5

8 3.1

6 1.8

Torque Value

(Kgf-m)

Remarks

Brake cushion guide bolts cap

Brake drain valve

Rear brake arm bolts

Tightening nut for steering rod

Front shaft nut

Mounting bolt for handle

Mounting nut for front hub

Mounting bolt for front brake disc

Rear shaft nut

Nut for rear hub

2

1

1

1

1

1

4

3

1

4

6 1.0

6 0.6

5 0.55

25.4 7.0

12 6.0

10 5.0

8 2.5

8 4.5

14 11.0

8 2.5

1-8

This chapter Contents

1. GENERAL INFORMATION

Cables and Harness Routing

Note the following when routing cables
and wire harnesses:

• A loose wire, cable or harness may cause

safety hazard. After clamping, check each
wire to make sure it is secured.

• Do not squeeze wires against the weld or its

clamp.

• Secure wires and wire harnesses to the

frame with respective wire bands at the
designated locations. Tighten the bands so
that only the insulated surfaces contact the
wires or wire harnesses.

• Route harnesses so that they neither pull too

tight nor have excessive slack.

• Protect wires or wire harnesses with

electrical tape or tube if they contact a sharp
edge or corner.

• Route wire harnesses to avoid sharp edges

or corners.

• Avoid the projected ends of bolts and

screws.

• Keep wire harnesses far away from the

exhaust pipes and other hot parts.

• Be sure grommets are seated in their groves

properly.

• After clamping, check each harness to be

certain that it is not interfered with any
moving or sliding parts.

• After routing, check that the wire harnesses

are not twisted or kink.

• Wire harnesses routed along the handlebar

should not be pulled too tight or have
excessive slack, be rubbed against or
interfere with adjacent or surrounding parts
in all steering positions.

• Thoroughly clean the surface where tape is

to be applied.

• Wrap electrical tape around the damaged

parts or replace them.

O：Correct
X：Wrong

1-9

This chapter Contents

1. GENERAL INFORMATION

Starter switch

Headlight switch

Speedometer

Winker switch

High/low beam switch

Horn switch

Front brake
lamp switch

Headlight

Throttle cable

Rear brake lamp switch

Front brake cable

Throttle cable

Main switch

Speedometer cable

Rear brake cable

Winker relay

1-10

Regulator

Horn

Resistor

Front brake hose

Speedometer cable

This chapter Contents

Front brake hose

Throttle cable

1. GENERAL INFORMATION

Speedometer cable

Rear brake cable

Winker relay

Fuel unit

Throttle cable

Front brake hose

Rear brake cable

Front brake hose

Rear brake cable

Throttle cable

Fuel unit cord

Fuel pump

Speedometer cable

Fuel filter

1-11

This chapter Contents

1. GENERAL INFORMATION

Fuse

Purge control valve

Battery

Fuel pump

Fuel filter

Oil control cable

Fuel hose

C.D.I. UNIT

Carburetor

Rear brake cable

Oil hose

Vacuum hose

Oil lever switch

1-12

This chapter Contents

1. GENERAL INFORMATION

Troubleshooting

A. Engine hard to start or can not be started

Check and adjustment Fault condition Probable causes

Loosen carburetor drain bolt
to check if there is gasoline
inside the carburetor

Fuel supplied tom
carburetor sufficient

No fuel is supplied to
carburetor

Remove spark plug, install
it into spark plug cap, and
perform a spark test
against engine ground.

Check if sparks

Week sparks or no spark
at all

Perform cylinder
compression pressure test.

cylinder compression pressure normal Low compression

pressure or no pressure

Re-start by following the
starting procedures

1. No fuel in fuel tank

2. Check if the pipes, fuel tank to
carburetor and intake vacuum, are
clogged.

3. Float valve clogged

4. Lines in fuel tank evaporation system
clogged

5. Malfunction of fuel pump

6. Loosen or damaged fuel pump vacuum
hose

7. Fuel filter clogged

1. Malfunction of spark plug

2. Spark plug foul

3. Malfunction of CDI set

4. Malfunction of AC generator

5. Ignition coil is in open or short circuit

6. Ignition coil leads open or short circuit

7. Malfunction of main switch

1. Piston ring seized

2. Malfunction of cylinder valves

3. Worn cylinder and piston ring

4. Cylinder gasket leak

5. Sand hole in compression parts

6. Crankcase leakage for pre-compression

No ignition

Remove the spark plug
again and check it.

Dry spark plug Wet spark plug

Remove carburetor after 30
minutes and connect a hose
onto fuel supplement circuit.
Then blow the hose with air

Blowing in normal

There are some signs of
ignition, but engine can
not be started

Blowing clogged

1. Malfunction of throttle valve operation

2. Air sucked into intake manifold

3. Incorrect ignition timing

1. Fuel level in carburetor too high

2. Malfunction of throttle valve operation

3. Throttle valve opening too wide

1. Malfunction of auto-starter

1-13

This chapter Contents

1. GENERAL INFORMATION

Engine run sluggish (Speed does not pick up, lack of power)

B.

Check and adjustment Fault condition Probable causes

Try gradual acceleration
and check engine speed

Engine speed can be
increased.

Engine speed can not be
increased.

Check ignition timing
(Using ignition lamp)

Ignition timing correct Incorrect ignition timing

Check cylinder compression
pressure (using compression
pressure gauge)

Compression pressure correct No compression pressure

Check if carburetor is
clogged

Normal Clogged

1. Air cleaner clogged

2. Poor fuel supply

3. Lines in fuel tank evaporation system
clogged

4. Exhaust pipe clogged

1. Malfunction of CDI

2. Malfunction of AC generator

1. Cylinder & piston ring worn out

2. Cylinder gasket leaked

3. Sand hole in compression parts

4. Valve deterioration

5. Crankcase leakage for
pre-compression

1. Remove dirt

Remove spark plug

No foul or discoloration Fouled and discoloration

Check if engine over heat

Continually drive in
acceleration or high speed

1-14

Normal Engine overheat

No knock Knock

1. Remove dirt

2. Incorrect spark plug heat range

1. Piston and cylinder worn out

2. Lean mixture

3. Poor fuel quality

4. Too much carbon deposited in
combustion chamber

5. Ignition timing too advanced

1. Too much carbon deposited in
combustion chamber

2. Lean mixture

3. Poor fuel quality

4. Lean mixture

This chapter Contents

1. GENERAL INFORMATION

Engine runs sluggish (especially in low speed and idling)

C.

Check and adjustment Fault condition Probable causes

Check ignition timing
(using ignition lamp)

Adjust the air screw of
carburetor

Air sucked through
carburetor gasket

Remove spark plug, install
spark plug into spark plug
cap and perform spark test
against engine ground

Engine runs sluggish (High speed)

D.

Normal

Good Poor

No air sucked

Good spark

Abnormal

Air sucked

Poor

1. Incorrect ignition timing (malfunction
of CDI or AC generator)

1. Rich mixture (loosen the screw)

2. Lean mixture (tighten the screw)

1. Poor heat insulation gasket

2. Carburetor lock loose

3. Poor intake gasket

4. Poor carburetor O-ring

1. Spark plug fouled

2. Malfunction of CDI

3. Malfunction of AC generator

4. Malfunction of ignition coil

5. Open or short circuit in spark plug
leads

6. Malfunction of main switch

CHECK AND ADJUSTMENT FAULT CONDITION PROBABLE CAUSES

Check ignition timing

Check for fuel supplying
system in automatic fuel cup

Normal

Good

Check if carburetor clogged

Abnormal

Poor

1. Malfunction of CDI

2. Malfunction of AC generator

1. Insufficient fuel in fuel tank

2. Fuel filter clogged

3. Restricted fuel tank vent

Normal

Clogged

1. Cleaning

1-15

This chapter Contents

1. GENERAL INFORMATION

. CLUTCH, DRIVING AND DRIVING PULLEY

E

FAULT CONDITION PROBABLE CAUSES

Engine can be started but
motorcycle can not be driving

Engine running and misfire as
motorcycle initial forward moving
or jumping sudden (rear wheel
rotating as engine in running)

Poor initial driving (Poor climbing
performance)

1. Driving belt worn out or deformation

2. Driving disk damaged

3. Driving pulley spring broken

4. Clutch ling broken

5. Driving slide-shaft gear groove broken

6. Transmission gear damage

7. Transmission gear worn out or burned

1. Clutch ling spring broken

2. Clutch outer cover stuck with clutch balance weights

3. Connection parts in clutch and shaft worn out or
burned

1. Driving belt worn out or deformation

2. Balance weight roller worn out

3. Driving sliding gear shaft worn out

4. Driving disk spring deformation

5. Driving sliding gear shaft worn out

6. Greased in driving belt and sliding gear.

1-16

This chapter Contents

1. GENERAL INFORMATION

Lubrication Points

Steering shaft bearing

Throttle cable/
Front & rear brake lever pivot

Engine suspension bushing

Seat lock

Speedometer gear/ front
wheel bearing

Side stand shaft

Main stand shaft

Rear wheel bearing

1-17

This chapter Contents

1. GENERAL INFORMATION

Note:

1-18

Home page

Contents

2. SERVICE MAINTENANCE INFORMATION

General Information·························2-1
Periodical Maintenance Schedule···2-2
Air Cleaner········································ 2-3
Fuel Lines ·········································2-3
Fuel Filter·········································· 2-4
Engine Oil Line································· 2-4
Oil Pump Control Cable··················· 2-5
Tire·····················································2-6
Battery···············································2-6
Rear Brake Free Play: (Drum Brake Type)

····························································2-7

Brake System Hose: (Front Disc Brake
Type)·················································· 2-8

Steering System·······························2-10

Suspension····································· 2-10
Transmission Oil····························2-11
Spark Plug ······································ 2-11
Control Cable Lubrication············· 2-12
Driver Belt······································· 2-12
Ignition Timing ······························· 2-12
Throttle Valve Operation················ 2-12
Carburetor Idle Speed Adjustment 2-13
Carbon Removing For Exhaust Pipe &

Muffle··············································· 2-13
Cylinder Compression Pressure Test
2-13
Headlight Adjustment···················· 2-14

2

General Information

Specification

Item

Tire dimension Front: 120 / 70 – 12, Rear: 130 / 70 - 12
Tire pressure at cold Only rider Front: 1.75kg/cm

Rear brake lever free play 10~20 mm
Transmission oil / Recommendation

Spark plug / Recommendation

Driving belt width
Ignition timing F mark

Acceleration operation 2~6 mm
Idle speed
Cylinder compression pressure

Type: HYPOID GEAR OIL
Oil: SAE #140 Quantity: 0.12 L Replacement: 0.11L

Type: NGK BR8 HSA

Plug gap: 0.6-0.7mm

JET 50 JET 100

Allowable limit: replace it if below 16.5mm

17 °, BTDC/1500 rpm

2000 ±100 rpm 2100 ±100 rpm

7 ±1 kgf/cm² 10 ±2 kgf/cm²

Model

2

Rear: 2.0 kg/cm2

Type: NGK BR6 HSA

Plug gap: 0.6-0.7mm

Standard 18.0mm

2-1

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2. SERVICE MAINTENANCE INFORMATION

Periodical Maintenance Schedule

Check item

☆

1. Air cleaner

☆

2. Fuel filter

☆

3. Engine oil filter cleaning

4. Oil pump linkage operation

☆

☆
☆

☆

☆
☆
☆

☆
☆
☆

☆

Have your scooter checked, adjusted periodically by your SYM Authorized Dealer to maintain the scooter at the
optimum condition

Code: I ~ Inspection, cleaning, and adjustment R ~ Replacement

The above maintenance schedule is established by taking the monthly 1000 kilometers as a reference which
ever comes first.

Remarks:

check

5. Tire pressure

6. Battery inspection

7. Brake & free play check

8. Steering handle check

9. Cushion operation check

10. Every screw tightening check

11. Gear oil check for leaking

12. Spark plug check or change

13. Gear oil change

14. Frame lubrication

15. Exhaust pipe

16. Carburetor

17. Driving belt check

18. Ignition timing

19. Emission check in Idling

20. Idle speed check

21. Fuel lines

22. Throttle operation

23. Engine bolt tightening

24. Engine screw torque

25. Carbon cleaning for cylinder
head, cylinder, piston head,
and exhaust system.

C ~ Cleaning (replaced if necessary) L ~ Lubrication

1. Clean or replace the air cleaner element more often for pro-long engine life-span when the
scooter is operated on dusty roads or in the Heavily- polluted environment.

2. Maintenance should be performed more often if the scooter is frequently operated in high speed
and after the scooter has accumulated a higher mileage.

Maintenance
kilometer

Maintenance
interval

300KM

New 1 month 3 month 6 month 1 year

I C R

C

C C

I I
I I

I I
I I
I I
I I
I I
I I
I R

R Replacement for every 5000km

L
I I
I I

I
I I
I I
I I
I I
I I
I I

I

I

Every

1000KM

Every

3000KM

Every

6000KM

Every

12000KM

Reference

2-2

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2. SERVICE MAINTENANCE INFORMATION

Air Cleaner

• Remove the mounting screw from the air
cleaner cover

• Remove the air cleaner cover

Remove the air cleaner element
Clean the element with non-flammable or
high-flash point solvent and then squeeze it for
dry.

Caution

Never use gasoline or acid organized solvent
to clean the element.

Mounting screw X 7

Air cleaner element

Soap the element into cleaning engine oil and
then squeeze it out. Install the element onto
the element seat and then install the air cleaner
cover.

• Limit to use SAE 20 JASO FC class engine

oil, otherwise, SYM is no responsible for the
warranty.

• Recommended engine oil: MAX-2 serial oils.

Fuel Lines

Remove the body cover
Check fuel lines and replace damaged lines if
found.
Install the body cover.

Squeeze oil out

Fuel pump

Clean

Soap

Squeeze out remaining oil

Carburetor

Fuel line

2-3

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2. SERVICE MAINTENANCE INFORMATION

Fuel Filter

Remove the luggage box.
Remove the fuel line from the fuel filter.
Replace the fuel filter with new one.
Install the fuel filter. The arrow indicates the fuel
flowing direction.
Check the fuel line for leaking.

Engine Oil Line

Remove the body cover.
Check the engine oil line and replace damaged
parts.
Remove the filling pipe from the oil pump, and
drain oil into a cleaning container.
Loosen the clamp under the engine oil tank, and
then remove the oil pipe.
Bleed the air inside the oil pump and oil pipe if
air found.
Install the body cover.

Fuel filter

Engine oil pipe

Oil pump

Oil filling pipe

2-4

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2. SERVICE MAINTENANCE INFORMATION

Oil Pump Control Cable

Caution

To adjust the oil pump control cable after
adjusted the throttle grip play.

Remove the body cover.
Wide open the throttle valve, and check if the
calibration point aligns on the oil pump lever with
the mark of pump body.
Loosen the adjustment nut of the oil pump
control cable.
Turn the adjustment nut and align with the point,
then tighten the nut.

Mounting nut

Adjustment nut

2-5

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2. SERVICE MAINTENANCE INFORMATION

Tire

Caution

Tire pressure should be checked when cold.

Check tire for cracks, damage, nail, or other
object stuck in tread.
Recommended tire and tire pressure

Tire size
Tire pressure

(cold) kg/cm

Check if the tire tread and wall rubber for crack
or damage, and replace if necessary.
Check if foreign materials such as nail, metal
pieces, and stones stuck on tire.
The thread depth can be checked by visual
inspection or by a depth gauge.

• If the tread bend too much, replace the tire.

• If tire wear exceeds limitation, replace the

tire, and check it for un-even wear.

Front:
120 / 90 - 10

2

1.75 2.0

Rear:
130 / 90 - 10

Caution

Wear indicator “△” is distributed on average
along the wall rubber for check.

Battery

Open the seat.
Loosen two screws of battery cap and then
remove the cap. Check if the battery
terminals are loosen. Remove the battery if its
terminals are corroded obviously.

Battery Removal

1. Remove the Negative (-) battery cable at
first.

2. Then, remove the Positive (+) battery cable.

3. Remove the battery.

Clean the rust with steel brush.
Install the battery in reverse order of removal,
and apply with grease onto two terminals.

Caution

The electrolyte is contained sulfuric acid so
be careful not to let it touch to eyes, skin, or
clothes. If touched by accident, flush them
with clean water immediately. However, if
the electrolyte sprays to eyes, medical care
should be done quickly.

Wear indicator

△ Mark

2-6

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2. SERVICE MAINTENANCE INFORMATION

Rear Brake Free Play: (Drum
Brake Type)

Measure the free play of the rear brake lever at
the end of the lever.
Free play: 10-20 mm (3/8-3/4 in)

Adjust the free play by turning the front brake
adjustment nut if necessary.

Brake Confirmation

Caution

After brake adjustment, it has to check the
brake operation to make sure the front and
rear wheel can be braked.

10∼20mm
(3/8∼3/4 in)

Adjustment nut

Decreasing
free play

Increasing
free play

2-7

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2. SERVICE MAINTENANCE INFORMATION

Brake System Hose: (Front Disc
Brake Type)

Make sure that the brake hose is corrosion or
damage, and also check the system for leaking.

Brake Fluid:

Check brake fluid level in the brake fluid
reservoir. If the level is lower than the LOWER
limit, add brake fluid DOT-3 to UPPER limit. Also
check brake system for leaking if low brake level
found.

Caution

z In order to maintain brake fluid in the

reservoir in horizontal position, do not
remove the cap until handle bar stop.

z Do not operate the brake lever after the cap

had been removed. Otherwise, the brake
fluid will spread out if operated the lever.

Lower limit

Brake fluid
reservoir cap

Arrow

z Do not mix non-compatible brake fluid

together.

Brake Lining Wear: (Rear Drum Brake
Type)

Replace the brake lining if the wear limit mark
“△” on the brake arm aligning with the indicator

of brake drum.

Brake Lining Wear: (Front Disc Brake
Type)

The arrow mark on brake lining is the wear
limitation.
Replace the brake lining if the wear limit mark
closed to the edge of brake disc.

Caution

In order to maintain brake power balance, the
brake lining must be replaced with one set.

Wear limit mark

Brake lining

Brake caliper

Brake disc

2-8

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2. SERVICE MAINTENANCE INFORMATION

z Remove the pin bolt cap.
z Loosen the bolt.
z Remove the front wheel shaft bolt.
z Take out the front wheel.

Remove brake caliper mounting bolt and then
remove the brake caliper.

Caution

Do not operate the brake lever after the
clipper removed to avoid clipping the brake
lining.

Pin bolt cap

Mounting bolt

Pry out the brake lining with a flat driver if lining
is clipped.

Remove brake lining bolt.
Take out the lining.

Tighten Torque:
Mounting bolt: 2.9-3.5 kgf-m
Pin bolt: 1.5-2.0 kgf-m
Pin bolt cap: 0.8-1.2 kgf-m

The brake LIGHT switch is to light up brake
LIGHT as brake applied. Replace the switch if
the light does not light up in properly.

Caution

The brake light switch is un-adjustable.

Pin bolt

Brake lining

Pin bolt

2-9

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2. SERVICE MAINTENANCE INFORMATION

Steering System

Caution

The control cables can not interfere with the
rotation of steering handle.

Lift the front wheel out of ground, and check if
the steering handle turning is smoothly.
If handle turning is uneven and bending, stuck,
or the handle can be operated in vertical
direction, then adjust the handle top bearing by
adjusting the steering nut.

Suspension

Warning

Do not ride the scooter with poor suspension.
Looseness, wear or damage suspension
system will make poor stability and
drive-ability.

Front Shock Absorber

Press down the front shock absorber for several
times to check it operation.
Check if the shock absorber assembly is
damage. Replace it if damage found and can
not be repaired.
Tighten all nuts and bolts.

Rear Shock Absorber

Park the scooter with its main stand.
Shake the rear wheel side to side to check
engine suspension bushing for wear.
Replace the bushing if looseness found.
Check the shock absorber for damage.
Tighten all nuts and bolts.

Nuts, Bolts Tightness

Check if all bolts and nuts on the frame are
tightened to specified torque in accord with the
interval of Periodical Maintenance Schedule.
Check all split pins, snap rings, hose clamps,
and wire holders for security.

2-10

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2. SERVICE MAINTENANCE INFORMATION

Transmission Oil

Leak

Check if the transmission is leak.

Check

Caution

Park the scooter on flat ground with its main
stand.

Remove the oil level check bolt, and check if the
oil level is placed on the hole of check bolt.

Replacement

Remove the oil level check bolt.

Remove the oil draining bolt, and then drain oil
out.
Install the oil draining bolt.

Tighten torque: 1.3 kg-m

Caution

Check if oil seal and washer is in good
condition.

Replacement Quantity: 0.09 L (90 cc)
Recommended oil: King Bramax HYPOID
GEAR OIL #140

Spark Plug

Oil level check bolt

Draining bolt

Oil level check bolt hole

Recommended plug: NGK BR8HSA

z Remove the luggage box.
z Remove the spark plug cap.
z Clean any dirt on the spark plug seat.
z Remove the spark plug.
z Visually inspect the spark plug electrodes

for wear.

z The center electrode should have square

edges and side electrode should have a
constant thickness. Replace the spark plug
if there is apparent wear or if the insulator is
cracked and/or chipped. If the spark plug
deposits can be removed by sandpaper, the
spark plug can be reused.

z Measure the spark plug gap with feeler

gauge.

Spark plug gap: 0.6-0.7mm
(0.024-0.028in)

z Adjust the gap by careful bending the side

electrode.

z Install the spark plug by screwing it with

hands after installed the spark plug washer
so that can prevent the plug from out of
thread. Then, tighten the spark plug with a
spark plug wrench.

z Install the spark plug cap.

0.6~0.7mm

Center electrode

Side electrode

2-11

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2. SERVICE MAINTENANCE INFORMATION

Control Cable Lubrication

Remove the throttle control and the brake cables
periodically, and lubricate the moving parts of
the cables thoroughly.

Driver Belt

z Remove left crankcase cover.
z Check if the belt is crack or worn out.

Replace the belt if necessary.

z Measure the driving belt width

Allowable limit: 16.5mm

Ignition Timing

Caution

z C.D.I ignition timing can not be adjusted. If

the ignition timing is incorrect, check the
C.D.I. device and the alternator and
replace damaged components.

Tooth face

Ignition lamp

Belt width

“F” mark

z Check ignition timing with standard

instrument.

Remove the right-side cooling fan cover.
Check ignition timing with the timing light.
When engine speed setting to 1800 rpm, and if
the mark aligns with “F” mark, then it means that
the ignition timing is correct.

Throttle Valve Operation

Check if each steering positions are operated in
smooth, and handle bar if its operation is
smooth as the throttle valve wide opening or
fully closed.
Check throttle cable and replace it if deteriorated,
twisted or damaged.
Lubricate the cable if operation is not smooth
Measure throttle valve handle free play.

Free play：2~6 mm (1/8-1/4 in)

Loosen the mounting nut, and turn the free play
adjustment nut of the throttle valve handle for
adjustment.
Replace the cable if it can not be adjusted.

2-12

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2. SERVICE MAINTENANCE INFORMATION

Carburetor Idle Speed Adjustment

Caution

z Inspection & adjustment for idle speed

have to be performed after all parts in
engine had been adjusted in specification.

z Idle speed check and adjustment have to

be done after engine is being warn up. It
around operates engine from stop to
running for 10 minutes.

Remove the body cover.
Park the scooter with main stand after warned
up engine. According to the required idling and
air screw to adjust to specified idle speed.

Idle speed: 2000±100 rpm (JET 50)
Idle speed: 2100±100 rpm (JET 100)

Carbon Removing For Exhaust
Pipe & Muffle

Remove the body cover.
Remove the exhaust pipe & muffler.
Clean the carbon deposits on the muffler &
cylinder exhaust edge.

Pilot screw

Idle speed adjustment screw

Adjust the idling after warn up engine for 10
minutes.

1. Connect tachometer.

2. Adjust the idle speed screw to let engine
speed in 2000±100 rpm.

3. Insert the sampling pipe of the CO/HC meter
to the test hole on the front end of exhaust
pipe. Adjust the idling emission value to
standard range. (CO: 1.8-2.6%)

4. Slightly accelerate the throttle valve and
release it. Repeat this operation for 1-2
times.

5. Read the engine idle speed and the emission
value after engine speed in stable. Repeat
the operation on step No. 2 – No. 4. until
these value within standard range.

Compression pressure gauge

Cylinder Compression Pressure
Test

Remove the left body cover, and warn up engine.
Stop the engine and remove the spark plug.
Insert the compression gauge and wide open
the throttle, and then rotate the engine by means
of the starting motor.

Compression pressure: 7.0±1 kg/cm

Probable causes for low compression pressure.

z Damaged cylinder head gasket.
z Worn piston ring
z Worn cylinder

Probable causes for high compression pressure.

z Carbon on the combustion chamber or

cylinder head

2

2-13

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JET Euro

JET

2. SERVICE MAINTENANCE INFORMATION

Headlight Adjustment

Loosen headlight mounting bolt.
Move the headlight for adjustment its light beam.
Tighten the headlight mounting bolt after
adjusted.

Caution

Improper headlight beam adjustment will
make in coming driver dazzled or insufficient
lighting for safety distance.

Headlight mounting bolt

Headlight mounting bolt

2-14

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Contents

3. LUBRICATION SYSTEM

Lubrication System Diagram············3-1
Precautions In Operation··················3-2
Lubricant············································3-2
Trouble Shooting·······························3-2

Lubrication System Diagram

Oil Pump Removal···························· 3-3
Oil Pump Installation························ 3-3
Oil Pump/Oil Tube Air Bleeding······· 3-4
Oil Tank ············································· 3-5

Oil lever switch

3

Oil output tube

Oil tank

Oil tube

Oil pump

3-1

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3. LUBRICATION SYSTEM

Precautions In Operation

z Be careful not let dirt enter into engine or oil hoses when removing or installing the oil pump.
z If air is found in the oil tube (from oil tank to oil pump) or oil tube is removed, the oil pump should

be conducted air-bleeding operation.

z It should bleed the oil output tube (from oil pump to carburetor) as hose removed.
z The adjustment of oil pump control cable.

Lubricant

z Appointed to apply SAE 20 JASO FC class oil. Otherwise, warranty shall not cover the damage.
z Recommended Oil: MAX-2 oil.
z Oil tank capacity: 1.2 lit.

Trouble Shooting

Too much smoke, carbon in spark plug.

1. Improperly oil pump adjustment (too much oil).

2. Poor quality oil.

3. Applying with poor quality oil.

Over heat

1. Improperly oil pump adjustment (insufficient oil).

2. Poor quality oil.

3. Applying with poor quality oil.

Piston seized

1. No oil in oil tank or clogged hose.

2. Improperly oil pump adjustment (insufficient oil).

3. Air in oil hose.

4. Malfunction of oil pump.

Oil did not flow out the oil tank

1. Clogged breath hole on the oil tank cover.

3-2

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3. LUBRICATION SYSTEM

Oil Pump Removal

Caution

Before removing the oil pump, clean the oil
pump and crankcase.

Remove the luggage box and seat.
Loosen the mounting nut of the oil pump control
cable, and remove the control cable.
Remove the oil tube, and clip its end side to
prevent oil from flowing out.

Remove the oil output tube form intake manifold.
Remove the oil pump mounting bolt, and then
take out the oil pump.

Inspection

Inspect the following items on the removed oil
pump.

z Check if O-ring is damaged or softening.
z Check if crankcase interface is damaged.
z Check if pump body is damaged.
z Check if pump gear is damaged.
z Check for oil leaking.

Oil output tube

Control cable

Mounting nut

Oil tube

Adjustment nut

Oil output tube

Caution

The oil pump can not be disassembled.

Oil Pump Installation

Install the oil pump onto the crankcase.

Caution

z Apply with some grease onto oil pump

O-ring.

z The connection between both oil pump and

crankcase has to be installed in position
security.

Tighten the oil pump mounting bolt security.
Install the oil tube.
Installation in the reverse order of removal.

Caution

Inspection and adjustment following items as
installed.
The adjustment operation of control cable.
Air bleeding operation of oil pump.
Air bleeding operation of oil tube.
Check each section for leaking.

3-3

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3. LUBRICATION SYSTEM

Oil Pump/Oil Tube Air Bleeding

Caution

The oil tube system has to be conducted air
bleeding operation because air will clog or
restraint oil flowing so that cause serious
engine damage.

Caution

After disconnect the oil tube, air enters oil
tube due to oil leak out without added oil.
There is why the oil tube and oil pump have to
conduct air bleeding operation.

Oil Tube/Oil Pump

z It has to add some oil into the oil tank.
z Place a piece of dry cloth around the oil

pump.

z Disconnect the oil tube.
z Fill out oil to oil pump connection section by

means of the oil pot so that the oil pump body
is full with oil.

z Fill out oil to oil tube connection section so

that the oil tube is full with oil. Then, install
the tube onto oil pump.

z Make sure whether air is in the oil tube or not

after installation.

Oil output tube

Oil tube

Oil tube

Control cable

Caution

After bleeding the oil tube and oil pump, the
oil tube has to be conducted air bleeding
operation too.

Oil Tube Air Bleeding

Remove the oil output tube and plug its input
connector. Bend the oil tube into “U “shape,
and fill out new oil into the output tube.
Connect the oil output tube to the oil pump
connection part.
Start engine, and run it in idling as the oil control
lever in wide open position. Make sure oil flows
out from the oil output tube.

Caution

z Motorcycle’s exhaust gas includes with CO

which causes human to coma or death so
perform this operation in well-ventilation
place.

z Run the engine in extreme low speed to

avoid to damaging the engine caused from
clogged oil tube.

Oil output tube

Recommended oil

3-4

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3. LUBRICATION SYSTEM

Oil Tank

Removal/Installation

Remove the luggage box and seat.
Remove the battery and battery box.

Remove the R/L. side cover, rear center cover,
rear carrier and body cover.

Remove the rear fender.
Remove the oil input tube from oil pump, and
then drain oil to a clean container.
Remove the oil switch wire of the oil indicator.

Remove the mounting bolt on the oil tank upper
side, and then remove the oil tank.
Installation in the reverse order of removal.
Air bleeding the oil tubes after installation.

Mounting bolt

Blot ×2

Screw ×2

Blot ×1

3-5

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3. LUBRICATION SYSTEM

NOTES:

3-6

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Contents

4. ENGINE REMOVAL

Maintenance Information ················ 4-1

Engine installation····························4-4

Engine removal································ 4-2

Maintenance Information

There are parts that require removal of engine for maintenance.

z Crankcase
z Crankshaft

Related bolts tightening torque for removal of engine:
Engine hanger bolt 5.0kgf-m

Engine bracket bolt 6.0kgf-m
Rear shock absorber upper mounting bolts 4.0kgf-m
Rear shock absorber lower mounting bolts 2.7kgf-m
Exhaust pipe connection nut 1.2kgf-m

4

Muffle mounting bolt 3.3kgf-m

4-1

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4. ENGINE REMOVAL

Engine removal

Remove body cover.
Remove the spark plug cap from the spark plug
section.

Remove the fuel output and the vacuum tubes
from fuel pump.
Remove the oil control cable from oil pump.
Remove the oil tube from oil pump and then clip
the tube.

Remove the wire connectors of auto by starter
and ACG.

Remove the upper part of the carburetor from its
upper side.
Remove the vapor emission vacuum tube from
carburetor intake manifold.

Vacuum tube

Fuel output tube

Fuel pump

Spark plug

Oil tube

Oil control cable

Wire connector

4-2

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4. ENGINE REMOVAL

Remove rear brake cable from engine rear-lower
side.

Remove air cleaner mounting bolts. (2 bolts)

Support the engine and then remove shock
absorber lower mounting bolt.

Remove two exhaust pipe connection nuts.
Remove two bolts beside fan cover and exhaust
pipe.

Brake cable

Mounting bolt

Shock absorber lower
mounting bolt

Connection nut

Exhaust pipe

Bolt

4-3

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4. ENGINE REMOVAL

Remove engine mounting nut and bolt.

Engine installation

Install in the reverse order of removal
procedures.
Tighten the engine mounting and rear shock
absorber upper/lower bolts.

Torque value:

Engine mounting bolt

Engine hanger bolt:
Rear shock absorber upper

mounting bolts:
Rear shock absorber lower

mounting bolts:
Exhaust pipe connection nut:
Muffle mounting bolt:

5.0kgf-m

4.0kgf-m

2.7kgf-m

1.2kgf-m

3.3kgf-m

Perform the following inspection and adjustment
after installation.

z Check if control cable is correct.
z Check if throttle valve cable is correct.
z Check if oil pump control cable is correct.
z Oil input and output of the oil pump.
z Adjust rear brake.

4-4

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Contents

5. CYLINDER HEAD/CYLINDER/PISTON

Maintenance Information··················5-2
Troubleshooting································5-2

Cylinder Head·····································5-3
Cylinder/Piston···································5-5

5

5-1

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5. CYLINDER HEAD/CYLINDER/PISTON

Maintenance Information

Precautions In Operation

z The inspection and maintenance of the cylinder head, cylinder and piston can be carried as

engine mounted on the body.

z It should clean the engine to prevent dirt from entering into cylinder and crankcase before

removal.

z Remove all washes from the interfaces of cylinder head, cylinder and crankcase.
z Be careful do not damage cylinder head, cylinder and piston when removing.
z Inspect the removed & cleaned parts thoroughly, and apply with oil onto the rotation surfaces

before installation.

Specification

JET 50 series JET 100 series

Item

Cylinder

head

Piston

Cylinder

ID: inner diameter
OD: outer diameter

Deformation - 0.100 - 0.100
Piston OD 39.030~39.045 38.935 51.030~39.045 50.935

Clearance between
cylinder and piston
Piston pin hole 12.002~12.008 12.030 14.002~14.008 14.030
Piston pin OD 11.994~12.000 11.970 13.994~14.000 13.970
Clearance between
piston and piston pin
Piston ring end gap 0.100~0.250 0.400 0.100~0.250 0.400
ID of connecting rod
small end
ID 39.000~39.015 39.050 51.000~51.015 51.050
Deformation - 0.100 - 0.100

Tighten torque value

Cylinder head
Spark plug

Standard value

(mm)

0.040~0.050 0.100 0.040~0.050 0.100

0.002~0.014 0.030 0.002~0.014 0.030

17.05~17.015 17.025 17.05~17.015 17.025

1.0 kgf-m

1.4 kgf-m

Limit (mm)

Exhaust pipe connection nut
Exhaust muffler mounting bolt

Standard value

(mm)

Limit (mm)

1.2 kgf-m

3.3 kgf-m

Troubleshooting

Compression Pressure Too Low/Difficult
To Start/Rough Idling

1. Cylinder head gasket leaking

2. Spark plug not tighten enough

3. Worn, seized or crack piston ring

4. Damaged, worn cylinder or piston

5. Poor reed

Compression Pressure Too
High/Overheat/Knock

1. Too much carbon deposit built up in
combustion chamber

5-2

Piston Noise

1. cylinder and piston worn out

2. piston pin or piston pin hole worn out

3. connecting rod small end bearing worn out

Piston Ring Noise

1. Worn, seized or crack piston ring

2. Cylinder worn out or damaged

This chapter Contents

5. CYLINDER HEAD/CYLINDER/PISTON

Cylinder Head

Cylinder Removal

Removal body covers.
Remove spark plug cap.
Remove fan cover.
Remove engine shield.

Remove two connection nuts of the exhaust
pipe.
Remove exhaust muffle mounting bolt, and then
remove the exhaust pipe.

Cylinder Head Removal

Remove the 4 cylinder head bolts and then
remove the cylinder head.

Tightening bolt

Muffle

Tightening bolts

Tightening bolt

Engine shield

Tightening bolt x 2

Bolt x 2

Caution

Loosen the cylinder head bolts with diagonal
direction to avoid to damaging it.

Cleaning Carbon In Combustion
Chamber

Clean carbon deposit in which built up in
combustion chamber with shown chisel.

Caution

Do not scratch to the interfaces of combustion
chamber and cylinder.

Chisel

5-3

This chapter Contents

5. CYLINDER HEAD/CYLINDER/PISTON

Cylinder Head Inspection

Use a straight edge and a feeler gauge to
measure the cylinder head for warp.

Service limit: 0.10 mm

Cylinder Head Installation

Replace the cylinder head gasket with new one,
and place the cylinder head onto cylinder.
Tighten the 4 bolts with diagonal direction and
by 2-3 sequences.

Tighten torque: 1.0 kgf-m

Install spark plug

Tighten torque: 1.4 kgf-m

Replace the exhaust pipe washer with new one
and then install exhaust pipe.
Tighten exhaust pipe connection nut.

Tighten torque: 1.2 kgf-m

Tighten exhaust pipe mounting bolt.

Tighten torque: 3.3 kgf-m

Install the removed parts in the reverse order of
removal procedures.
Inspect following item after installation.
Compression pressure test.
Check for engine noise.

Tightening bolts

Tightening bolt x 2

5-4

Muffle

Bolt x 2

This chapter Contents

5. CYLINDER HEAD/CYLINDER/PISTON

Cylinder/Piston

Cylinder Removal

Be careful to pull the cylinder up and prevent
piston from damage.

Caution

Do not have pry out operation between
cylinder and crankcase. Or let radiation fan
be knocked seriously.

Piston Removal

Place a clean rag onto crankshaft to cover the
piston.
Remove piston pin clip (one piece) and then
push piston pin out the piston.

Caution

Piston

y Do not damage or scratch the piston.
y Do not apply with lateral force to

connecting rod.

y Do not let piston pin snap ring falling into

crankcase.

Piston Ring Removal

Caution

Pry out the opening end of each piston ring
and then remove the ring from piston.

Check if cylinder and piston are worn or
damaged, and then clean carbon deposit on
exhaust opening area as the diagram shown.

Piston pin clip

Piston pin

Caution

Do not scratch both the cylinder and the
piston.

5-5

This chapter Contents

5. CYLINDER HEAD/CYLINDER/PISTON

Use a straight edge and a feeler gauge to
measure the cylinder head for warp.

Service limit: 0.10 mm

In “X” and “Y” direction, measure the cylinder for
worn out as the three levels shown in the figure.
With the max. value to decide cylinder wear out
condition.

Service limit
JET 50 : 39.050mm
JET 100 : 51.050mm

Measure the OD of piston at the 7 mm from the
bottom of the piston.

Service limit
JET 50 : 38.935 mm
JET 100 : 50.935 mm

Calculate the clearance between piston and
cylinder.

Service limit: 0.100 mm

Measure the ID of piston pin hole.

Service limit
JET 50 : 12.030mm
JET 100 : 14.030 mm

Measure the OD of piston pin.

Service limit
JET 50 : 11.970 mm
JET 100 : 13.970 mm

7mm

The ID of piston pin hole

The OD of piston pin

5-6

This chapter Contents

5. CYLINDER HEAD/CYLINDER/PISTON

Piston Ring Inspection

Measure the end gap of each piston ring.

Service limit: 0.40 mm

Caution

With the piston, push each piston ring into
cylinder correctly.

Connecting Rod Inspection

Install bearing and piston pin onto connecting
rod small end, and then check its clearance.
Measure the ID of connecting rod small end.

Service limit: 17.025mm

Piston/Cylinder Installation

Install the expanding ring into the groove of 2nd
ring.
Align the ring end with the lock pin in the ring
groove.
Install the top ring and the 2
groove respective.

nd

ring onto the ring

Clearance

Top ring

2nd ring

Piston ring mark

Caution

The top ring and the 2nd ring can not be
changeable each other.

Push the rings into ring groove and then check
rings’ mating condition.
If ring could not be push in the ring groove, it
means that ring groove is dirty or wrong ring
groove installation.

Caution

y All rings should be installed with the marks

facing up.

y All ring should be replaced at same time,

and it can not be replaced one ring only.

y It should use same brand name piston ring

in an engine and can not mix with other
one.

Expanding ring

1T: top ring

nd

2T: 2

ring

5-7

This chapter Contents

5. CYLINDER HEAD/CYLINDER/PISTON

Place a cleaning cloth onto the crankcase
opening to prevent the piston pin snap ring from
falling into the crankcase.
Apply with two-stroke engine oil onto needle
bearing and piston pin, and then install the
piston pin onto connecting rod. Install piston,
and place “EX” mark of the piston toward to
exhaust side.
Install new piston pin snap ring.

Clean all gaskets onto the interfaces of cylinder
and crankcase.
Place a new gasket onto the crankcase.
Make sure that the piston ring aligns with the
lock pin in piston ring groove.

Caution

Piston

〝EX〞mark

Piston pin

Piston pin snap ring

Make sure that all rings in the piston ring
groove can not be rotated around the lock pin
to avoid to damaging the rings, piston and
cylinder.

Lubricate cylinder and piston with two-stroke
engine oil. Hold the piston and then install it
into cylinder.

Caution

To avoid to damaging the piston and the
cylinder sliding surface.

Install the cylinder head.

Lock pin

5-8

Home page

Contents

6. ALTERNATOR

Maintenance Information ················ 6-2

Alternator Removal·························· 6-3

3.8 kgf-m

Alternator Installation······················· 6-4

6

6-1

This chapter Contents

6. ALTERNATOR

Maintenance Information

Precautions in Operation

z The maintenance service of A.C. alternator can be carried out directly on the motorcycle.
z Please refer to Chapter 15 for the relative alternator inspection.

Torque value:

Flywheel 3.8 kgf-m

Tool

General tool

Rotor puller
Universal holder

Coil resistance value for the A.C. alternator

JET 50/100 series

Earth 50~200Ω 0.2~0.8Ω 0.2~1.0Ω 400~800Ω

Y/L Y W R/B Earth

JET EURO 50/100 series

Earth 50~200Ω

Y 0.4~0.8Ω

Y/L Y

AC.G

L/Y

Y

Y

3P

Y

6-2

This chapter Contents

6. ALTERNATOR

Alternator Removal

Remove the body cover.
Remove two bolts and then take out cooling fan
cover.

Remove four bolts, and then take out the cooling
fan.

Hold flywheel with universal holder.
Support the flywheel and the remove the 10 mm
nut on the flywheel.

Remove the flywheel with rotor puller.

Cooling fan cover

Bolt

Cooling fan

10mm flanged nut

Universal holder

Rotor puller

6-3

This chapter Contents

6. ALTERNATOR

Disconnect alternator wire connector and pulse
generator connector.

Remove the pulse generator and alternator four
(4) bolts, and then take out the alternator
assembly.

Caution

Care to be taken for not damaging the
alternator coil.

Wire harness connector

10mm flanged nut

Alternator Installation

Install the alternator assembly.
Connect the alternator connector.

Caution

Connect the alternator wire harness properly
and then clip the harness with clipper.

Install the woodruff key onto the crankshaft
groove.

Caution

z Clean dirt and metal pieces inside the

flywheel.

z Make sure that there is no foreign material

inside the flywheel.

Install the flywheel

Tighten the flywheel 10 mm nut.

Torque value: 3.8 kgf-m

Install the removed parts in reverse order of
removal procedures.
Start engine and check its ignition timing.

Universal holder

6-4

Home page

Contents

7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Maintenance Information ················ 7-2
Trouble Shooting····························· 7-2
Left Crankcase Cover······················ 7-3
Reassembly Of Kick Starter············ 7-4
Installation Of The Left Crankcase

Cover················································· 7-4

Drive Belt···········································7-5
Movable Driven Pulley ·····················7-6
Clutch/Driven Pulley·························7-10

5.5 kgf-m

7

3.8 kgf-m

3.8 kgf-m

7-1

This chapter Contents

7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Maintenance Information

Precautions In Operation

The surfaces of drive belt and driven pulley must be free of grease.

Specification

Item Standard value(mm) Limit(mm)
Drive belt width
ID of movable drive face
OD of movable drive face boss
OD of weight roller
ID of clutch outer
Thickness of clutch weight
Free length of driven pulley spring
OD of driven pulley
ID of movable driven face

ID: Inner Diameter
OD: Outer diameter

Torque Values:

Movable drive face: 3.8 kgf-m
Driven pulley: 5.5 kgf-m
Clutch outer: 3.8 kgf-m

18.0 16.5

20.035~20.085 20.120

23.964~23.985 23.918

15.92~16.08 15.40

107.0~107.2 107.5

4.0~4.1 2.0

87.9 82.5

33.965~33.985 33.940

33.000 34.060

Special Service Tools

Clutch spring compressor
Bearing driver
Clutch nut wrench 39x41 mm
Bearing driver accessory 39x41 mm
Universal holder
Driver

Trouble Shooting

Engine can be started but motorcycle
can not be moved

1. Worn drive Belt

2. Worn ramp plate

3. Worn or damaged clutch weight

4. Broken driven pulley spring

Shudder or misfire when drive

1. Broken clutch weight

2. Worn clutch weight

7-2

Insufficient horsepower or poor high
speed performance

1. Worn drive belt

2. Insufficient spring capacity of driven pulley

3. Worn weight roller

4. Driven pulley operation un-smoothly

This chapter Contents

7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Left Crankcase Cover

Left crankcase cover removal

Remove left body side cover.
Remove air cleaner.
Remove kick start arm.
Remove left crankcase cover.

Disassembly of Kick Starter

Remove snap clip and thrust washer from left
crankcase cover.
Install kick start arm, rotate the lever slightly and
then remove driven gear and washer.
Remove the kick starter arm, kick starter spindle,
and return spring as well as socket.

Left crankcase cover

Kick start arm

Return spring

Starter spindle

Driven gear

Inspection of kick Starter

Check if starter spindle, driven gear for wear or damage.

Return spring

Bush

Bolt

Kick start arm

Snap ring

Thrust washer

Thrust washer

Starter spindle

Driven gear

Friction spring

7-3

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7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Reassembly Of Kick Starter

Install bush, return spring and starter spindle as
diagram shown.
Install thrust washer and snap clip onto starter
spindle.
Install Kick starter lever temporary.
Slightly rotate the lever and then align driven
gear with width-tooth on the starter spindle.
Install the friction spring of drive gear onto
convex part of the cover.

Installation Of The Left Crankcase
Cover

Install the dowel pin and gasket.
Install the left crankcase cover.

Install kick start arm.

Return spring

Dowel pin

Width-tooth

Convex part

Kick starter spindle

Driven gear

Friction spring

7-4

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7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Drive Belt

Removal

Remove left crankcase cover.
Hold clutch outer with universal holder, and
remove nut and clutch outer.

Caution

y Using special tools for tightening or

loosening the nut.

y Fixed rear wheel or rear brake will damage

reduction gear system.

Push the drive belt into belt groove as diagram
shown so that the belt can be loosened, and
then remove the driven pulley.
Remove driven pulley/clutch. Do not remove
drive belt.
Remove the drive belt from the groove of driven
pulley.

Inspection

Check the drive belt for crack or wear. Replace
it if necessary.
Measure the width of drive belt as diagram
shown.

Service Limit: 16.5 mm

Replace the belt if exceeds the service limit.

Nut

Universal holder

Clutch/drive belt

Belt tooth

Caution

y Using the genuine parts for replacement
y The surfaces of drive belt or pulley must be

free of grease.

y Clean up all grease or dirt before

installation.

Installation

Caution

y Pull out driven pulley to avoid it closing.

Install drive belt onto driven pulley.

Movable driven
pulley

7-5

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7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Install the driven pulley that has installed the belt
onto drive shaft.

Install the clutch with universal holder, and then
tighten nut to specified torque value.

Torque value: 3.8 kgf-m

Drive face

Clutch/driven pulley

Nut

Drive belt

Universal holder

Drive shaft

Clutch outer

Movable Drive Face

Removal

Remove left crankcase cover.
Hold generator flywheel with universal holder,
and then remove drive face nut.

Remove drive face.

Universal holder

Flywheel

Nut

7-6

Drive face

This chapter Contents

7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Removal

Remove movable drive face set and drive belt
from crankshaft.

Remove ramp plate.

Drive face boss

Crankshaft

Movable drive face

Ramp plate

Remove weight rollers from movable face.

Inspection

The weight roller is to press movable driven face
by means of centrifuge force. Thus, if weight
rollers are worn out or damage, the centrifuge
force will be affected.
Check if rollers are wear out or damage.
Replace it if necessary.
Measure each roller’s outer diameter. Replace it
if exceed the service limit.

Service limit: 15.40 mm

Movable drive face

Weight roller

Weight roller

7-7

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7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Check if movable drive face boss is worn or
damage and replace it if necessary.
Measure the outer diameter of drive face boss,
and replace it if it exceed service limit.

Service limit: 19.98 mm

Measure the inner diameter of drive face, and
replace it if it exceed service limit.

Service limit: 20.120 mm

Reassembly / Installation

Install weight rollers.

Install ramp plate.

Apply with grease 4~5g to inside of movable
drive face, and install drive face boss.

Caution

Movable drive face

Drive face boss

Weight roller

Ramp plate

Drive face

y The drive face has to be free of grease.

Clean it with cleaning solvent.

7-8

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7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Install movable drive face assembly onto
crankshaft.

Drive Face Installation

Press drive belt into pulley groove, and then pull
the belt on to crank shaft.

Drive face boss

Crankshaft

Press down

Movable drive face

Drive belt

Install drive face, washer and nut.

Caution

y Make sure that two sides of drive face have

to be free of grease. Clean it with cleaning
solvent.

Hold flywheel with universal holder.

Tighten nut to specified torque.

Torque value: 3.5-4.0 kgf-m

Install left crankcase cover.

Flywheel

Universal holder

Nut

Drive face

7-9

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7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Clutch/Driven Pulley

Disassembly

Remove drive belt and clutch/driven pulley.
Install clutch spring compressor onto the pulley
assembly, and operate the compressor to let nut
be installed more easily.

Caution

y Do not press the compressor too much.

Hold the clutch spring compressor onto bench
vise, and then remove mounting nut with clutch
nut wrench.
Release the clutch spring compressor and
remove clutch and spring from driven pulley.
Remove socket from sliding pulley.

Remove guide pin, guide pin roller, and driven
pulley, and then remove O-ring & oil seal seat
from sliding pulley.

Inspection

Sliding pulley

O-ring

Oil seal

Clutch nut
wrench

Clutch spring
compressor

Socket

Guide pin

or

Guide pin roller

Clutch outer

Measure the inner diameter of clutch outer
friction face. Replace clutch outer if exceed
service limit.

Service limit: 107.5 mm

7-10

Inner
diameter

Clutch outer

This chapter Contents

7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Clutch weight

Measure each clutch weight thickness.
Replace it if exceeds service limit.

Service limit: 2.0 mm

Driven pulley spring

Measure the length of driven pulley spring.
Replace it if exceeds service limit.

Service limit: 82.5 mm

Driven pulley

Check following items:

y If both surfaces are damage or wear.
y If guide pin groove is damage or wear.

Replace damaged or worn components.
Measure the outer diameter of driven pulley and
the inner diameter of sliding pulley. Replace it
if exceeds service limit.

Service limit: Outer diameter 33.94 mm

Inner diameter 34.06 mm

Driven Pulley Bearing Inspection

Check if the inner bearing oil seal is damage.
Replace it if necessary.
Check if needle bearing is damage or too big
clearance. Replace it if necessary.
Rotate the inside of inner bearing with fingers to
check if the bearing rotation is in smooth and
silent. Check if the bearing outer parts are
closed and fixed. Replace it if necessary.

Clutch weight

Free length

Driven pulley

Sliding pulley

Guide pin groove

Needle bearing

Caution

y Some of models are equipped with two ball

bearings.

Outer ball bearing

7-11

This chapter Contents

7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Clutch Block Replacement

Remove clip and washer, and then remove
clutch weight and spring from drive plate.

Caution

y Some of models are equipped with one

mounting plate instead of 3 snap clips.

Check if spring is damage or insufficient
elasticity.

Check if shock absorption rubber is damage or
deformation. Replace it if necessary.
Apply with grease onto lock pins.

Install new clutch weight onto lock pin and then
push to specific location.
Apply with grease onto lock pins. But, the
clutch weight should not be greased. If so,
replace it.

Clutch weight

Shock absorption
rubber

Shock absorption rubber

Spring

Drive plate

Snap clip

Caution

y Grease or lubricant will damage the clutch

weight and affect the weight’s connection
capacity.

Install the spring into groove with pliers.

Clutch block

Spring

7-12

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7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Install snap clip and mounting plate onto lock
pin.

Replacement of Driven Pulley Bearing

Remove inner bearing.

Caution

y If the inner bearing equipped with oil seal

on side in the driven pulley, then remove
the oil seal firstly.

y If the pulley equipped with ball bearing, it

has to remove snap clip and then the
bearing.

Remove snap clip and then push bearing
forward to other side of inner bearing.

Place new bearing onto proper position and its
sealing end should be forwarded to outside.
Apply with specified grease.

Install new inner bearing.

Caution

Outer bearing

Snap clip

Inner needle bearing

Sealing end

Inner bearing

Snap clip

Clip

Inner ball bearing

Specified grease

Snap ring

Outer bearing

Sealing end

y Its sealing end should be forwarded to

outside as bearing installation.

y Install needle bearing with hydraulic

presser. Install ball bearing by means of
hydraulic presser or driver.

Install snap clip into the groove of drive face.
Align oil seal lip with bearing, and then install the
new oil seal (if necessary).

7-13

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7. “V” TYPE BELT DRIVE SYSTEM/KICK-STARTER

Installation of Clutch/Driven Pulley
Assembly

Install new oil seal and O-ring onto sliding pulley.
Apply with specified grease to lubricate the
inside of sliding pulley.

Install sliding pulley onto driven pulley.
Install guide pin and guide pin roller.

Install socket.

Install driven pulley, spring and clutch into clutch
spring compressor, and press down the
assembly by turning manual lever until mounting
nut that can be installed.
Hold the compressor by bench vise and tighten
the mounting nut to specified torque with clutch
nut wrench.
Remove the clutch spring compressor.

Torque value: 5.0~6.0 kgf-m

Install clutch/driven pulley and drive belt onto
drive shaft.

Oil seal

O-ring

Sliding pulley

O-ring

Mounting nut

Oil seal

Guide pin

Specified grease

Guide pin

or

Guide pin roller

Socket

Clutch nut
wrench

Clutch spring
compressor

7-14

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Contents

8. FINAL DRIVING MECHANISM

Maintenance Information················· 8-2
Troubleshooting······························· 8-2
Disassembly of Final Driving

Mechanism········································ 8-3

Inspection of Final Driving Mechanism

····························································8-4
Bearing Replacement·······················8-4
Re-Assembly of Final Driving

Mechanism········································8-4

8

8-1

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8. FINAL DRIVING MECHANISM

Maintenance Information

Limited usage of gear oil：gear oil #140
Recommended oil：Bramax serial oil.
Oil quantity：120 c.c. (110 c.c. as replacement)

Special tools:

Inner type bearing puller (SYM-6204020)
Outer type bearing puller (SYM-6204010)
Final shaft oil seal installer (SYM-9125500)
Drive shaft oil seal installer (SYM-9120200)
Bearing driver 6204 (SYM-9110400)
Bearing driver 6201 (SYM-9610001)
Bearing driver 6203/6004UZ (SYM-9620000)
L. crank puller (SYM-1130000-L)
L. crank shaft install bush (SYM-1130010)

Troubleshooting

Trouble Diagnosis
Engine can be started but scooter can not be moved.

1. Damaged drive gear

2. Burnt out or seized drive gear

Noise

1. Seized, worn or damage gear

2. Worn or loose bearing

Gear oil leaks

1. Excessive gear oil.

2. Worn or damage oil seal

8-2

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8. FINAL DRIVING MECHANISM

Disassembly of Final Driving
Mechanism

Remove driven pulley
Drain gear oil out from gearbox.
Remove rear wheel.
Remove gearbox cover mounting bolts from the
clutch side and then remove the cover from the
rear wheel side.

Remove final gear, final shaft and counter gear,
counter shaft.

Remove the drive shaft from left crankcase.

Caution

Final gear & shaft

Oil filling hole

Oil draining hole

Counter gear & shaft

Drive shaft

y The bearing must be replaced when

removing the drive shaft.

Remove drive shaft oil seal and bearing from left
crankcase.

Oil seal

Bearing

8-3

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8. FINAL DRIVING MECHANISM

Inspection Of Final Driving
Mechanism

Check if the drive shaft, counter shaft and final
gear shaft are worn or damage.
Check if the gear box cover bearing, oil seal and
the inner diameter of counter shaft are worn or
damage.
Check if the left crankcase cover bearing, oil
seal and the inner diameter of countershaft are
worn or damage.

Bearing Replacement

Caution

y Never install used bearings. Once bearing

removed, it has to be replaced with new
one.

Remove gear box bearing from left crankcase
and gear box cover using following tools:

Special tool:

Inner type bearing puller

Final driven gear & shaft

Countershaft

Drive shaft

Re-Assembly Of Final Driving
Mechanism

Re-assemble the gearbox cover and left
crankcase with special tools:

Special tool:
Gear Box Cover

Final shaft bearing:
Bearing driver 6203/6004UZ (SYM-9620000)
Bearing driver 6201 (SYM-9610001)
Final shaft oil seal installer (SYM-9125500)

Left Crankcase

Drive shaft bearing:
Bearing driver 6203/6004UZ (SYM-9620000)
Bearing driver 6201 (SYM-9610001)
L. crank puller (SYM-1130000-L)
L. crank shaft install bush (SYM-1130010)
Drive shaft oil seal installer (SYM-9120200)

With the special service tools to install drive
shaft by through the bearing.
Install a new drive shaft oil seal.
Install a new final shaft oil seal.

Driver

Punch guide

Adapter

Drive shaft

8-4

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8. FINAL DRIVING MECHANISM

Install countershaft, final driven gear and thrust
washer.

Install new gasket and lock pin.

Install gearbox cover.
Install clutch/driven pulley assembly.
Install driven pulley, drive belt, and left
crankcase side cover.
Install body cover.
Install rear wheel.
Fill out specified oil quantity into gearbox.

Final driven gear & shaft

Counter gear & shaft

8-5

This chapter Contents

8. FINAL DRIVING MECHANISM

Notes:

8-6

A

Home page

Contents

9. CRANKCASE/CRANKSHAFT

Maintenance Information····················9-2
Troubleshooting··································9-2
Crankcase Disassembly·····················9-3

1.0 kgf-m

Crankshaft Removal···························· 9-3
Crankshaft Inspection························· 9-4
Crankcase Installation························· 9-5

pply liquid gasket

9

9-1

This chapter Contents

9. CRANKCASE/CRANKSHAFT

Maintenance Information

z This chapter concerns disassembly of the crankcase for repair purpose.
z Before disassembling crankcase, except removing engine firstly, following components must be

removed too.

• Carburetor (chapter 10)

• Oil pump (chapter 3)

• Reed valve (chapter 10)

• Driving belt (chapter 7)

• Alternator (chapter 6)

• Cylinder head/cylinder/piston (chapter 5)

z Except above components are needed be removed, when disassembling L crankcase, following

components must be removed too.

• Final driving mechanism (chapter 8)

z When assembling both crankcase and crankshaft, it has press the inner ring edge of the

crankshaft bearing to push the crankshaft into the crankcase hole by using the specified service
tools. The old bearing onto the crankshaft has to be removed. Then install a new bearing onto the
crankshaft on the crankcase side. Oil seal has to be replaced with new one after assembled the
crankcase.

Item Standard Limit (mm)
Lateral clearance of the big end of the connecting rod
Radial clearance of the big end of the connecting rod
Crankshaft run-out point A
Crankshaft run-out point B

─
─
─
─

0.60

0.04

0.10

0.10

Special Tools

Crankcase disassemble tool (SYM-1120100-G5)
Outer bearing puller (SYM-6204010)
R. Crank shaft puller (SYM-1130000-R)
R. Crank shaft install bush (SYM-1130020)
L. Crank shaft puller (SYM-1130000-L)
L. Crank shaft install bush (SYM-1130010)
20*32*6 Oil seal driver (SYM-9120200)
Bearing driver 6204 (SYM-9110400)

Troubleshooting

Engine noise

1. Worn bearing of connecting rod bog end

2. Bend connecting rod

3. Worn crankshaft bearing

9-2

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9. CRANKCASE/CRANKSHAFT

Crankcase Disassembly

Remove the crankcase bolts.

Install the crankcase puller onto the right
crankcase with two (2) bolts, 6mm, as the
diagram shown.
Disassemble the right crankcase.

Bolts

Crankcase puller

Crankshaft Removal

As the diagram show with 3 special bolts to
install the specified service tool onto the left
crankcase.
Remove the crankcase.

Caution

Do not use iron hammer to knock out the
crankshaft.

Remove crankshaft bearing with bearing puller.
Remove the right and left side oil seals.

Caution

Right crankcase

Crankcase puller

Left crankcase

Replace the oil seal with new one as
removing the crankshaft.

Shaft protection collar

Outer bearing puller

9-3

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9. CRANKCASE/CRANKSHAFT

Crankshaft Inspection

Measure the clearance of connecting rod big
end.

Service limit: 0.60 mm

Measure the radial clearance of connecting rod
big end at X-Y directions as diagram show.

Service limit: 0.04 mm

Place the crankshaft on a V-block, measure
run-out points A and B of the crankshaft with dial
gauge.

Service limit: A: 0.10 mm

B: 0.10 mm

Check the crankshaft bearing by means of
turning it with hand. If any noise and bigger
clearance are detected, replace the bearing with
new one.

A

70mm

B

37mm

Clearance

Clearance

9-4

Lateral

Radial

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9. CRANKCASE/CRANKSHAFT

Crankcase Installation

Clean the crankshaft with solvent and blow it
with compressed air. Then, check for damage
or other foreign materials attached.
Install new bearing into right crankcase.

Caution

y All rotation and sliding surfaces have to be

applied with clean engine oil.

y Remove all gaskets onto the crankcase

interfaces and flat it with special tool.

Install new bearing into left crankcase.

Install crankshaft onto the left crankcase.
Install left crankshaft puller and install bush onto
crankshaft.
Screw the left crankshaft puller onto crankshaft.
Turn the puller in C.W. direction and then
completely screw the puller to bottom.
Lubricate crankshaft bearing and bearing seat
with 2-stroke engine oil.

Apply liquid gasket and dowel pin onto the
interface of left crankcase.

Bearing driver 6204

Bearing driver 6204

L. Crank shaft puller

Collar

L. Crank shaft install bush

Apply liquid gasket

Dowel pin

9-5

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9. CRANKCASE/CRANKSHAFT

Assemble the right crankcase with assembly
tools.
Install right crankcase onto the crankshaft.
Install right crankshaft puller and install bush
onto crankshaft.
Screw the right crankshaft puller onto
crankshaft.
Turn the puller in C.W. direction and then
completely screw the puller to bottom.
Lubricate crankshaft bearing and bearing seat
with 2-stroke engine oil.

Install the bolts and tighten them.

Torque value: 1.0 kgf-m

With right crank shaft install bush, install new oil
seal into the right crankcase. Its installation
depth is 4mm as the diagram shown.

R. Crank shaft puller

R. Crank shaft
install bush

Bolts

R. Crank shaft
install bush

With the specified tool to install a new oil seal
onto the left crankcase to the depth of 1 mm as
the diagram shown.

Caution

Make sure that the crankshaft can be rotated
freely after tightening the bolts.

Install the following components:
~ Final driving mechanism (chapter 8)
~ Alternator (chapter 6)
~ Piston/cylinder/cylinder head (chapter 7)
~ Oil pump (chapter 3)
~ Reed valve and carburetor (chapter 10)
~ Engine (chapter 4)

Oil seal

Oil seal driver

9-6

Home page

Contents

10. FUEL SYSTEM

Maintenance Information ·················10-2
Troubleshooting ·······························10-2
Throttle Valve····································10-3
Carburetor Remove··························10-4
Auto By-Starter·································10-4
Float/Float Valve/Jet·························10-6

Vacuum hose

Flaot Level Inspection······················10-7
Carburetor Installation·····················10-7
Reed Valve ········································10-7
Fuel Pump·········································10-8
Air Cleaner ········································10-9

Throttle valve cable

Air hose

Oil tube

Fuel unit

Fuel cap

Fuel pump

Fuel filter

Carburetor

Vacuum tube

10

Fuel tank

10-1

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10. FUEL SYSTEM

Maintenance Information

Precautions in Operations

Warning

Gasoline is a highly flammable material and may explosive under circumstance. Thus, always work
in a well-ventilated place and strictly prohibit flame when working with gasoline.

y Care must be taken when dealing with gasoline, and always work in a well-ventilated place and

strictly prohibit flame.

y When disassembling fuel system parts, pay attention to O-ring position, replace with new one as

re-assembly

y It has to conduct air bleeding operation as removed the oil tube.
y Idle speed adjustment.

Specification

Item JET 50 JET 100
Venturi diameter 15 mm 16 mm
Fuel level

Air screw opener 1 3/8
Idle speed

Throttle handle free play 2~6 mm

2000±100 rpm 2100±100 rpm

8.8±1.0mm

Troubleshooting

Engine can not be started

1. No fuel in fuel tank

2. Fuel can not reach to carburetor

3. Too much fuel in cylinder

4. Clogged air cleaner

Stall after started

1. Incorrect idle speed adjustment

2. No spark on the spark plug

3. Low compression pressure

4. Rich mixture

5. Lean mixture

6. Clogged air cleaner

7. Inlet pipe leaking

8. Polluted fuel

Lean Mixture

1. Clogged carburetor jet

2. Clogged hose from carburetor to canister

3. Bend, squeezed or clogged fuel lines

4. Clogged fuel filter

5. Malfunction of float valve

6. Low fuel level in float chamber

7. Clogged vent pipe

8. Malfunction of fuel pump

Rich Mixture

1. Malfunction of float valve

2. Low fuel level in float chamber

3. Clogged carburetor air injector

10-2

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10. FUEL SYSTEM

Throttle Valve

Removal

Remove the body cover.
Remove the carburetor upper part, throttle valve
spring and sealed cap.
Remove the throttle valve cable from the throttle
valve.
Remove needle clamp and fuel needle.

Inspection

Carburetor
upper part

Oil hose

Throttle valve spring

Sealed cap

Needle clamp

Throttle valve cable

Fuel needle clip

Fuel needle

Carburetor upper part

Washer

Throttle valve

Installation

Place the fuel needle onto the throttle valve and clip it with needle clamp.
Install the sealed cap, carburetor upper part, and throttle valve spring.
Connect the throttle valve cable to the throttle valve.
Install the throttle valve into the carburetor body.

Caution

Align the groove inside the throttle valve with the throttle stopper screw of the carburetor body.

Tighten the carburetor upper part.
Install carburetor protector.
Adjust the free play of throttle valve cable.

10-3

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10. FUEL SYSTEM

Carburetor Remove

Remove the body cover.

Disconnect the auto by-starter connector.

Loosen draining screw and then drain out fuel
inside the carburetor.
Loosen carburetor upper part and remove
carburetor upper part.
Remove fuel and oil hoses from carburetor.
Remove carburetor mounting bolt and
carburetor.

Auto by-starter

Fuel hose

Bolt

Carburetor
upper part

Auto By-Starter

Inspection

Connect resistor meter to the terminals of auto
by-starter, and then measure its resistance.
If the resistance value exceeds specification too
much, it means that the PTC in the auto
by-starter is malfunction. Then, replace the
auto by-starter.

Resistance value: Max. 10Ω(at cold engine)

Caution

If the resistance value exceeds the standard a
little bit, the auto by-starter may still in normal.
However, it is necessary to check other
relative components for damage.

10-4

Draining screw

Auto by-starter

Connection hose clamp

This chapter Contents

10. FUEL SYSTEM

Remove carburetor, and allow it to cool off for 30
minutes.
Connect fuel rich circuit with a hose and pump
compressed air to the hose.
Air should flow into fuel rich circuit.
Replace the auto by-starter if the circuit clogged.

Connect battery to starter’s connectors and wait
for several minutes.
Pump compressed air into the fuel rich circuit.
Air should not flow into the circuit.
If air flow through the circuit, then, replace the
starter.

Check resistor to make sure that the auto
by-starter is in normal. Engine is running.
If the resistor is in open-circuit, then current will
not flow into the PTC. Thus, the auto by-starter
is not operated.
However, if the resistor is in short-circuit, current
higher than specification will flow into the PTC.
Then, it will cause the fuel rich circuit close
rapidly, and difficult to start the scooter.

Resistance value: 10.2Ω

Battery

Alternator

Resistor

Automatci By-Starter
Removal/Installation

Remove the cover of the auto by-starter.
Remove screw and mounting plate.
Remove the auto by-starter from carburetor.
Install in the reverse order of removal
procedures.

Auto by-starter

Screw

Mounting plate

10-5

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10. FUEL SYSTEM

Float/Float Valve/Jet

Removal

Remove the float from carburetor body.
Remove the float pin and then remove float and
float valve.
Check the valve seat for worn out or damage.
Check float for bend and if fuel inside the float.
Before removing both the throttle valve stopper
and air screws, record their original turns for
close to their original set up position as
installation.

Caution

Do not tighten the screw forcedly to avoid to
damaging the valve seat.

Remove main jet, needle jet seat and idle jet
and clean them and each component with
compressed air.

Installation

Install the idle jet, the needle jet seat and main
jet. Then install the throttle valve stopper and air
screws to their original position according to the
marks as removal. Adjust the screws if replace
with new ones.

Float cap

Air inlet for
fuel rich
circuit

Air inlet for idle speed

Idle jet

Air screw

Float

Throttle valve
stopper screw

Needle jet

Needle jet seat

Main jet

Screw

Float valve

Float pin

O-ring

Float cap

Draining screw

10-6

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10. FUEL SYSTEM

Flaot Level Inspection

Measure float fuel level to have the upper end of
float just contact with the float.

Float fuel level: 8.8 mm

Carefully bend the float arm for adjustment.
Check the float operation and the install it.

Carburetor Installation

Caution

Do not let foreign materials into the
carburetor.

Install the carburetor and insulator onto intake
pipe with bolts.
Install fuel and vent pipes onto carburetor.
Install the carburetor upper part.
Tighten the connection hose.
Tighten the draining screw.
Connect the automatic by-starter connector.
Install air cleaner cap.
Conduct following operations

y Adjustment of throttle valve cable.
y Adjustment of oil pump.
y Adjustment of idle speed.

Fuel hose

Bolt

Draining screw

Carburetor
upper part

Connection hose clamp

Inlet pipe

Reed Valve

Removal

Remove the body cover.
Remove the carburetor.
Remove carburetor insulator.
Remove inlet pipe.
Remove the reed valve.

Reed valve

10-7

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10. FUEL SYSTEM

Inspection

Check the reed valve for damage and its reed
strength.
Check the reed valve seat for crack, damage
and the clearance between the seat and the
valve.
Replace reed valve if necessary.

Caution

Do not bend the reed valve stopper.
Otherwise, it will cause its strength insufficient
and rough engine running. If the reed valve
or its seat is damaged, replace with a set.

Installation

Install in the reverse order of removal
procedures.
Check for leaking after installed.

Fuel Pump

Inspection

Remove the body cover.
Warm up the engine and adjust idle speed.
Remove fuel hose from carburetor and then wait
for 5 minutes.
Measure the output of fuel pump. Its output
time is 10 seconds.

Output quantity: Min. 20 c.c.

If the output quantity is lower than 20 c.c., check
fuel hose, vacuum hose and fuel filter.

Removal/Installation

Remove floor plate.
Remove fuel inlet, outlet and vacuum hoses.
Remove 2 bolts and fuel pump.
Install the fuel pump in the reverse order of
removal procedures.

Reed valve

Reed valve seat

Fuel hose

Fuel inlet
hose

Reed stopper

Carburetor

Fuel hose
connector

Bolt

Fuel outlet
hose

Vacuum
hose

10-8

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10. FUEL SYSTEM

Air Cleaner

Removal/Installation

Loosen connection hose clamp.
Remove 2 bolts and then remove the air
cleaner.

Install in the reverse order of removal
procedures.

Hose clamp

Bolts

10-9

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10. FUEL SYSTEM

Notes:

10-10

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Contents

11. BRAKE SYSTEM

Front Disc Brake System···············11-1
Rear Drum Brake System ··············11-2
Maintenance Information···············11-3
Troubleshooting·····························11-4
Hydraulic Disc Brake······················11-5

Front Disc Brake System

Disc Brake -Air Bleed······················· 11-6
Disc Brake - Caliper ························· 11-6
Brake Disc········································· 11-7
Disc Brake - Master Cylinder··········· 11-7
Drum Brake······································· 11-10

2.5 kgf-m

0.55 kgf-m

3.5 kgf-m

11

1.8 kgf-m

1.0 kgf-m

4.5 kgf-m

6.0 kgf-m

11-1

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11. BRAKE SYSTEM

Rear Drum Brake System

11.0 kgf-m

2.5 kgf-m

0.55 kgf-m

11-2

r

This chapter Contents

11. BRAKE SYSTEM

Maintenance Information

Precautions in Operation

Caution

Inhaling brake lining ashes may cause disorders of respiration system, therefore, never use air
hose or dry brush to clean brake parts. Use vacuum cleaner or other authorized tool instead.

y The brake caliper can be removed without removing the hydraulic system.
y After the hydraulic system is removed, or the brake system is felt to be too soft, bleed the hydraulic

system.

y While refilling brake fluid, care should be taken not to let the foreign material entering into the

brake system.

y Do not spill brake fluid on the painted surfaces, plastic or rubber parts to avoid damage.
y Check the operation of the brake system before you go.

Specifications

Item Standard (mm) Limit (mm)
The thickness of front brake disc 3.5 2.0
Front brake disc run-out < 0.10 0.3
Master cylinder inner diameter 12.700 – 12.743 12.55

Master cylinder piston outer
diamete

ID of rear brake drum 110.0 110.5
Thickness of front brake lining 4.0 2.0
Thickness of rear brake lining 4.0 2.0

12.657 – 12.684 12.654

Torque values

Brake hose bolt 3.5 kgf-m
Bolt for brake caliper 3.3 kgf-m
Bolts for the lining guide pin 1.8 kgf-m
Bolts for the lining guide pin cap 1.0 kgf-m
Air-bleed valve 0.55 kgf-m
Bolts for the brake disc 4.5 kgf-m
Nuts for the wheel rim 2.5 kgf-m
Nuts for the front wheel 6.0 kgf-m
Nuts for the rear wheel 11.0 kgf-m
Bolt for rear brake arm 0.55 kgf-m

11-3