KYMCO MXU 50 REVERSE, MXU 50, MX'ER 50 Service Manual

By KWANG YANG Motor Co., Ltd.

First Edition, Jan 2006

All rights reserved. Any reproduction or

unauthorized use without the written permission of

KWANG YANG Motor Co., Ltd.

is expressly prohibited.

T100LB10DE

PREFACE

This Service Manual describes the
technical features and servicing
procedures for the KYMCO MXU 50
REVERSE/MXU 50/MX’ER 50.

Section 1 contains the precautions for
all operations stated in this manual.
Read them carefully before starting any
operation.

Section 2 is the removal/installation
procedures for the frame covers which
are subject to higher removal/installation
frequency during maintenance and
servicing operations.

Section 3 describes the inspection/
adjustment procedures, safety rules and
service information for each part,
starting from periodic maintenance.

Sections 4 through 19 give instructions
for disassembly, assembly and
inspection of engine, chassis frame and
electrical equipment.

Most sections start with an assembly or
system illustration and troubleshooting
for the section. The subsequent pages
give detailed procedures for the section.

KWANG YANG MOTOR CO., LTD.

OVERSEAS SALES DEPARTMENT

OVERSEAS SERVICE SECTION

TABLE OF CONTENTS

GENERAL INFORMATION 1
FRAME COVERS/EXHAUST MUFFLER 2
INSPECTION/ADJUSTMENT 3
LUBRICATION SYSTEM 4
FUEL SYSTEM 5
ENGINE REMOVAL/INSTALLATION 6
CYLINDER HEAD/CYLINDER/PISTON 7
A.C. GENERATOR 8
KICK STARTER/DRIVE

PULLEY/CLUTCH/DRIVEN PULLEY

9

FINAL REDUCTION
(MXU 50/MX’ER 50)

10

FINAL REDUCTION/TRANSMISSION
SYSTEM (MXU 50 REVERSE)

11

CRANKCASE/CRANKSHAFT 12
FRONT WHEEL/FRONT BRAKE/

FRONT SUSPENSION/STEERING
SYSTEM

13

REAR WHEEL /SWING
ARM/HYDRAULIC BRAKE

14

BATTERY/CHARGING SYSTEM/A.C.
GENERATOR

15

IGNITION SYSTEM 16
STARTING SYSTEM 17
LIGHTS/SWITCHES 18
ONLY ATV ON ROAD AVAILABLE 19

The information and contents included in
this manual may be different from the
ATV in case specifications are changed.

KYMCO reserves the right to make
changes at any time without notice and
without incurring any obligation.

ENGINE

CHASSIS

ELECTRICAL

EQUIPMENT

1. GENERAL INFORMATION

1-0

ATV 50

1

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

GENERAL INFORMATION

__________________________________________________________________________________

SERIAL NUMBER---------------------------------------------------------- 1- 1
SPECIFICATIONS---------------------------------------------------------- 1- 2
SERVICE PRECAUTIONS------------------------------------------------ 1- 5
TORQUE VALUES --------------------------------------------------------- 1-13
SPECIAL TOOLS ----------------------------------------------------------- 1-14
LUBRICATION POINTS -------------------------------------------------- 1-14
CABLE & HARNESS ROUTING (MX’ER 50) ------------------------ 1-17
CABLE & HARNESS ROUTING (MXU 50 REVERSE/MXU 50) - 1-21
WIRING DIAGRAM (MX’ER 50 ON ROAD) ------------------------- 1-26
WIRING DIAGRAM (MX’ER 50 OFF ROAD) ------------------------ 1-27
WIRING DIAGRAM (MXU 50 ON ROAD)---------------------------- 1-28
WIRING DIAGRAM (MXU 50 REVERSE ON ROAD)-------------- 1-29
TROUBLESHOOTING----------------------------------------------------- 1-30

1

1. GENERAL INFORMATION

1-1

ATV 50

SERIAL NUMBER

Location of Frame Serial Numbe

r

Location of Engine Serial Numbe

r

1. GENERAL INFORMATION

1-2

ATV 50

SPECIFICATIONS

Model No. LA10
Name MX’ER 50
Overall length 1685 mm (67.4 in)
Overall width 980 mm (39.2 in)
Overall height 1030 mm (41.2 in)
Wheel base 1120 mm (44.8 in)
Engine type Air cooled 2-stroke
Displacement 49.4 cm3 (2.964 cu-in)

Fuel Used

92# nonleaded
gasoline

Front wheel 67 kg (147.4 lbs)

Dry weight Rear wheel 73 kg (160.6 lbs)

Total 140 kg (308 lbs)
Front wheel 73 kg (160.6 lbs)

Curb weight Rear wheel 77 kg (169.4 lbs)

Total 150 kg (330 lbs)
Front wheel 20*7-8

Tires

Rear wheel 22*10-8
Ground clearance 130 mm (5.2 in)
Min. turning radius 2500 mm (100 in)

Starting system

Starting motor &

kick starter
Type Air cooled 2-stroke
Cylinder arrangement Single cylinder
Combustion chamber typeSemi-sphere
Valve arrangement Reed valve & piston

Bore x stroke

39 x 41.4 mm

(1.56 x 1.656 in)
Compression ratio 7.2:1

Compression pressure

12 kgf/c

m

2

(1200 kPa,

170.4 psi)

Open

Port

Intake

Close

Automatic controlled
timin

g

Open

Exhaust

Close

Automatic controlled

Intake －

Valve clearance

Exhaus

t

－

Idle speed (rpm) 1800

Lubrication type Separate type
Oil pump type Plunger type
Oil filter type Full-flow filtration

Air cleaner type Sponge
Fuel capacity 8.1 liters

Type PB
Main jet No. 80
Venturi dia φ14 mm (φ0.56 in)
Throttle type Valve piston

Type CDI

Ignition timing 22°/2000 rpm

Spark plug NGK-BR8HAS

Spark plug gap 0.6～0.7mm

Battery Capacity 12V4AH

Clutch Type CVT

Operation Automatic centrifugal

Type

Type Chain drive

Reduction 1st －

ratio 2nd －

Final gear ratio 23.678

Front Caster angle －
Axle Trail length －

Front 0.35 kgf/cm2 (35 kPa,

4.97 psi)

Tire pressure

Rear 0.35 kgf/cm

2

(35 kPa,

4.97 psi)
Turning Left 44°
angle Right 44°

Brake system Rear Disk brake
type Front Drum brake

Suspension Front Swing
type Rear Swing arm

Shock

Front Swing

type Rear Swing arm

Frame type SP pipe

Engine

Fuel S

y

stem

Carbureto

r

Electrical Equipment

I

g

nition S

y

stem

Power Drive System

Reduction

Gear

Moving Device

Damping

Device

1. GENERAL INFORMATION

1-3

ATV 50

Model No. LB10
Name MXU 50
Overall length 1775 mm (71 in)
Overall width 950 mm (38 in)
Overall height 1040 mm (41.6 in)
Wheel base 1120 mm (44.8 in)
Engine type Air cooled 2-stroke
Displacement 49.4 cm3 (2.964 cu-in)

Fuel Used

92# nonleaded
gasoline

Front wheel 87 kg (191.4 lbs)

Dry weight Rear wheel 89 kg (195.8 lbs)

Total 176 kg (387.2 lbs)
Front wheel 92 kg (202.4 lbs)

Curb weight Rear wheel 94 kg (206.8 lbs)

Total 186 kg (409.2 lbs)
Front wheel 21*7-10

Tires

Rear wheel 22*10-10
Ground clearance 165 mm (6.6 in)
Min. turning radius 2900 mm (116 in)

Starting system

Starting motor &

kick starter
Type Air cooled 2-stroke
Cylinder arrangement Single cylinder
Combustion chamber typeSemi-sphere
Valve arrangement Reed valve & piston

Bore x stroke

39 x 41.4 mm

(1.56 x 1.656 in)
Compression ratio 7.2:1

Compression pressure

12 kgf/c

m

2

(1200 kPa,

170.4 psi)

Open

Port

Intake

Close

Automatic controlled
timin

g

Open

Exhaust

Close

Automatic controlled

Intake －

Valve clearance

Exhaus

t

－

Idle speed (rpm) 1800

Lubrication type Separate type
Oil pump type Plunger type
Oil filter type Full-flow filtration

Air cleaner type Sponge
Fuel capacity 8.1 liters

Type PB
Main jet No. 80
Venturi dia φ14 mm (φ0.56 in)
Throttle type Valve piston

Type CDI

Ignition timing 22°/2000 rpm

Spark plug NGK-BR8HAS

Spark plug gap 0.6～0.7mm

Battery Capacity 12V8AH

Clutch Type CVT

Operation Automatic centrifugal

Type

Type Chain drive

Reduction 1st －

ratio 2nd －

Final gear ratio 23.678

Front Caster angle －
Axle Trail length －

Front 0.28 kgf/cm2 (28 kPa, 4

psi)

Tire pressure

Rear 0.28 kgf/cm

2

(28 kPa, 4

psi)
Turning Left 40°
angle Right 40°

Brake system Rear Disk brake
type Front Drum brake

Suspension Front Swing
type Rear Swing arm

Shock

Front Swing

type Rear Swing arm

Frame type SP pipe

Engine

Fuel S

y

stem

Carbureto

r

Electrical Equipment

I

g

nition S

y

stem

Power Drive System

Reduction

Gear

Moving Device

Damping

Device

1. GENERAL INFORMATION

1-4

ATV 50

Model No. LB10
Name MXU 50 REVERSE
Overall length 1786 mm (71 in)
Overall width 958 mm (38 in)
Overall height 1010 mm (40 in)
Wheel base 1105 mm (44 in)
Engine type Air cooled 2-stroke
Displacement 49.4 cm3 (2.964 cu-in)

Fuel Used

92# nonleaded
gasoline

Front wheel 78 kg (171.6 lbs)

Dry weight Rear wheel 80 kg (176 lbs)

Total 158 kg (347.6 lbs)
Front wheel 83 kg (182.6 lbs)

Curb weight Rear wheel 84 kg (184.8 lbs)

Total 167 kg (36734 lbs)
Front wheel 21*7-10

Tires

Rear wheel 22*10-10
Ground clearance 162 mm (6.6 in)
Min. turning radius 2900 mm (116 in)

Starting system

Starting motor &

kick starter
Type Air cooled 2-stroke
Cylinder arrangement Single cylinder
Combustion chamber typeSemi-sphere
Valve arrangement Reed valve & piston

Bore x stroke

39 x 41.4 mm

(1.56 x 1.656 in)
Compression ratio 7.2:1

Compression pressure

12 kgf/c

m

2

(1200 kPa,

170.4 psi)

Open

Port

Intake

Close

Automatic controlled
timin

g

Open

Exhaust

Close

Automatic controlled

Intake －

Valve clearance

Exhaus

t

－

Idle speed (rpm) 1800

Lubrication type Separate type
Oil pump type Plunger type
Oil filter type Full-flow filtration

Air cleaner type Sponge
Fuel capacity 8.1 liters

Type PB
Main jet No. 80
Venturi dia φ14 mm (φ0.56 in)
Throttle type Valve piston

Type CDI

Ignition timing 13.5°/1500 rpm

Spark plug NGK-BR8HAS

Spark plug gap 0.6～0.7mm

Battery Capacity 12V8AH

Clutch Type CVT

Operation

Automatic centrifugal
Type

Primary reduction
system

Helical gear/spur gear

Secondary reduction
system

Chain drive

Primary reduction ratio 1.2 – 3.5
Secondary reduction
ratio

20.12

Reverse ratio 46.11
Front Caster angle －

Axle Trail length －

Front 0.28 kgf/cm2 (28 kPa, 4

psi)

Tire pressure

Rear 0.28 kgf/cm

2

(28 kPa, 4

psi)
Turning Left 40°
angle Right 40°

Brake system Rear Disk brake
type Front Drum brake

Suspension Front Swing
type Rear Swing arm

Shock

Front Swing

type Rear Swing arm

Frame type SP pipe

Engine

Fuel S

y

stem

Carbureto

r

Electrical Equipment

I

g

nition S

y

stem

Power Drive System

Moving Device

Damping

Device

1. GENERAL INFORMATION

1-5

ATV 50

SERVICE PRECAUTIONS

 Make sure to install new gaskets, O-rings,

circlips, cotter pins, etc. when
reassembling.

 When tightening bolts or nuts, begin with

larger-diameter to smaller ones at several
times, and tighten to the specified torque
diagonally.

 Use genuine parts and lubricants.

 When servicing the motorcycle, be sure to

use special tools for removal and
installation.

 After disassembly, clean removed parts.

Lubricate sliding surfaces with engine oil
before reassembly.

1. GENERAL INFORMATION

1-6

ATV 50

 Apply or add designated greases and

lubricants to the specified lubrication
points.

 After reassembly, check all parts for proper

tightening and operation.

 When two persons work together, pay

attention to the mutual working safety.

 Disconnect the battery negative (-) terminal

before operation.

 When using a spanner or other tools, make

sure not to damage the motorcycle surface.

 After operation, check all connecting

points, fasteners, and lines for proper
connection and installation.

 When connecting the battery, the positive

(+) terminal must be connected first.

 After connection, apply grease to the

battery terminals.

 Terminal caps shall be installed securely.

1. GENERAL INFORMATION

1-7

ATV 50

 If the fuse is burned out, find the cause and

repair it. Replace it with a new one
according to the specified capacity.

 After operation, terminal caps shall be

installed securely.

 When taking out the connector, the lock on

the connector shall be released before
operation.

 Hold the connector body when connecting

or disconnecting it.

 Do not pull the connector wire.

 Check if any connector terminal is bending,

protruding or loose.

Confir

m

Capacity

1. GENERAL INFORMATION

1-8

ATV 50

 The connector shall be inserted

completely.

 If the double connector has a lock, lock

it at the correct position.

 Check if there is any loose wire.

 Before connecting a terminal, check for

damaged terminal cover or loose
negative terminal.

 Check the double connector cover for

proper coverage and installation.

 Insert the terminal completely.
 Check the terminal cover for proper

coverage.

 Do not make the terminal cover opening

face up.

 Secure wire harnesses to the frame with

their respective wire bands at the
designated locations.
Tighten the bands so that only the insulated
surfaces contact the wire harnesses.

Snapping!

1. GENERAL INFORMATION

1-9

ATV 50

 After clamping, check each wire to make

sure it is secure.

 Do not squeeze wires against the weld or

its clamp.

 After clamping, check each harness to

make sure that it is not interfering with any
moving or sliding parts.

 When fixing the wire harnesses, do not

make it contact the parts which will
generate high heat.

 Route wire harnesses to avoid sharp edges

or corners. Avoid the projected ends of
bolts and screws.

 Route wire harnesses passing through the

side of bolts and screws. Avoid the
projected ends of bolts and screws.

N

o Contact !

1. GENERAL INFORMATION

1-10

ATV 50

 Route harnesses so they are neither

pulled tight nor have excessive slack.

 Protect wires and harnesses with electrical

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

 When rubber protecting cover is used to

protect the wire harnesses, it shall be
installed securely.

 Do not break the sheath of wire.
 If a wire or harness is with a broken sheath,

repair by wrapping it with protective tape
or replace it.

 When installing other parts, do not press or

squeeze the wires.

Do not pull too
tight!

Do not press or
squeeze the wire.

1. GENERAL INFORMATION

1-11

ATV 50

 After routing, check that the wire harnesses

are not twisted or kinked.

 Wire harnesses routed along with

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

 When a testing device is used, make sure to

understand the operating methods
thoroughly and operate according to the
operating instructions.

 Be careful not to drop any parts.

 When rust is found on a terminal, remove

the rust with sand paper or equivalent
before connecting.

Do you understand the
instrument? Is the
instrument set
correctly?

Remove Rust !

1. GENERAL INFORMATION

1-12

ATV 50

 Symbols:

The following symbols represent the
servicing methods and cautions included in
this service manual.

: Apply engine oil to the

specified points. (Use
designated engine oil for
lubrication.)

: Apply grease for lubrication.

: Caution

: Warning

Engine Oil

Grease

Special

＊

＊

1. GENERAL INFORMATION

1-13

ATV 50

TORQUE VALUES

STANDARD TORQUE VALUES

Item

Torque

kgf-m (N-m, lbf-ft)

Item

Torque

kgf-m (N-m, lbf-ft)

5mm bolt and nut
6mm bolt and nut
8mm bolt and nut
10mm bolt and nut
12mm bolt and nut

14mm bolt and nut

0.5 (5, 3.6)
1 (10, 7.2)

2.2 (22, 16)

3.5 (35, 25)

5.5 (55, 40)
7 (70, 50)

4mm screw
5mm screw

6mm screw, SH bolt
6mm flange bolt and nut
8mm flange bolt and nut
10mm flange bolt and nut

0.3 (3, 2.2)

0.4 (4, 2.9)

0.9 (9, 6.5)

1.2 (12, 9)

2.7 (27, 20)
4 (40, 29)

Torque specifications listed below are for important fasteners.

ENGINE

Item Q‘ty Thread dia.(mm)

Torque

kgf-m (N-m,

lbf-ft)

Remarks

Cylinder head bolt
Clutch drive plate nut
Drive face nut
Clutch outer nut
A.C.G flywheel nut
Oil check/filler bolt (MXU 50/MX’ER 50)
Oil drain plug
Oil filler bolt (MXU 50 REVERSE)
Exhaust muffler joint lock nut
Exhaust muffler lock bolt
Spark plug

4
1
1
1
1
1
1
1
2
2

BF7X115
39
12
NH10
10
8
8
12
NC6mm
BF8X35

1.6 (16, 11.5)

5.5 (55, 40)

3.8 (38, 27)

3.8 (38, 27)

3.8 (38, 27)

1.2 (12, 9)
2 (20, 15)
2 (20, 15)

1.2 (12, 9)

3.3 (33, 24)

1.5 (15, 11)

FRAME

Item Q‘ty

Thread dia.(mm)

Torque

kgf-m (N-m,

lbf-ft)

Remarks

Steering stem nut
Swing arm nut
Rear wheel nut
Front wheel nut
Rear shock absorber upper mount bolt
Front shock absorber upper mount bolt

1
4
4
4
1
2

14
10
14
14
10
10

7 (70, 50)

4.5 (45, 32)
7 (70, 50)
7 (70, 50)
4 (40, 29)
4 (40, 29)

(Cont’d)

1. GENERAL INFORMATION

1-14

ATV 50

Item Q‘ty

Thread dia.(mm)

Torque

kgf-m (N-m,

lbf-ft)

Remarks

Front shock absorber lower mount bolt
Rear fork axle
Rear hub nut
Rear wheel shaft nut
Rear engine bracket up bolt
Rear engine bracket bolt
Engine hanger bracket bolt

2
1
4
2
1
2
1

10
14
12
32
10
10
10

4 (40, 29)
7 (70, 50)
7 (70, 50)
12 (120, 86)
4 (40, 29)
4 (40, 29)

4.5 (45, 32)

SPECIAL TOOLS

Tool Name Tool No. Memo
Flywheel puller A120E00001
Oil seal and bearing install A120E00014
Crankshaft install A120E00016
Universal holder A120E00017
Crankshaft & crankcase install A120E00024
Crankcase puller A120E00026
Crankshaft Bearing puller A120E00030
Clutch spring compressor A120E00034
Bearing puller A120E00037
Nut wrench A120F00010

LUBRICATION POINTS

ENGINE

Lubrication Points Lubricant

Crankcase sliding & movable parts
Cylinder movable parts
Transmission gear (final gear)
Kick starter spindle bushing
Drive pulley movable parts
Starter pinion movable parts

JASO-FC or API-TC
JASO-FC or API-TC
Gear oil: SAE90#
Grease
Grease
Grease

1. GENERAL INFORMATION

1-15

ATV 50

FRAME

The following is the lubrication points for the frame.
Use general purpose grease for parts not listed.
Apply clean engine oil or grease to cables and movable parts not specified. This will avoid
abnormal noise and rise the durability of the motorcycle.

Steering knuckle/Thrust
Cover/Bush/Colla

r

Steering Column Uppe

r

Rear Brake Cable

Front Brake
camshaft/Oil
Seal/O-ring

Throttle Cable

Front Brake Cable

Steering Column Lowe

r

Front Wheel
Oil Seal

Front Arm Bush

Front Brake
camshaft/Oil
Seal/O-ring

Front Wheel
Oil Seal

Steering knuckle/Thrust
Cover/Bush/Colla

r

Front Arm Bush

1. GENERAL INFORMATION

1-16

ATV 50

Sprocket hub/Rea

r

Axle Hub Collar/Oil
Seal/Bearing

Rear Brake Cam

/

Axle Hub Collar/Oil
Seal/Bearing

Driven Sprocket

Swing arm Thrust
Cove

r

1. GENERAL INFORMATION

1-17

ATV 50

CABLE & HARNESS ROUTING (MX’ER 50)

Throttle Cable

Rear Brake Cable

Right Front Brake Cable

Handlebar Switch Lea

d

Front Brake Cable

Left Front Brake Cable

A.C.G Wire
Starter Motor Wire
Auto Bystarter

1. GENERAL INFORMATION

1-18

ATV 50

Throttle Cable

Rear Brake Cable

Ignition Coil Wire

Fuel Tube

Fuel Filte

r

Oil Meter Wire

Right Front Brake Cable

Left Front Brake Cable

1. GENERAL INFORMATION

1-19

ATV 50

Wire Harness

Rectifier/Regulator

Oil Tube

Resistor

Ignition Coil

Right Front Brake Cable

1. GENERAL INFORMATION

1-20

ATV 50

Battery

Starter Relay

CDI Unit

Fuse

Rear Brake Cable

Breather Hose

Oil Meter Wire

Positive Cable

N

egative Cable

Main Switch

1. GENERAL INFORMATION

1-21

ATV 50

CABLE & HARNESS ROUTING (MXU 50 REVERSE/MXU 50)

Throttle Cable

Rear Brake Light Switch Wire

Front Brake Cable

Handlebar Switch Connectors

Right Front Brake Cable

Left Front Brake Cable

Fuel Tank Breather Hose

Left Headlight

/

Turn Signal Light Connector

Instrument Connecto

r

Horn

Ignition Switch
Connectors

Resisto

r

Right Headlight

/

Turn Signal Light Connectors

Front Brake Light
Switch Wire

Rear Brake Fluid Hose

1. GENERAL INFORMATION

1-22

ATV 50

Ignition Coil

Air Cleane

r

Fuel Valve

Inlet Hose

Oil Inlet Hose

Auto Choke Connecto

r

Starter Motor Connecto

r

Spark Plug Cap

Throttle Cables

N

eutral Switch Wire

(MXU 50 REVERSE)

Rear Brake Hose

1. GENERAL INFORMATION

1-23

ATV 50

Harness Wire

Ignition Coil Cable

Ignition Coil

Fuel Drain Hose

Hazard Unit

Headlight Control Unit

Ignition Coil Wire

Throttle Cable

Starter Motor Cable

ACG Wire

Fuel Unit Connectors

Transmission Case Breathe

r

Hose (MXU 50 REVERSE)

N

eutral Switch Wire (MXU 50 REVERSE)

Oil Outlet Hose

1. GENERAL INFORMATION

1-24

ATV 50

Rectifier/Regulato

r

CDI

Starter Moto

r

Speedometer wire

Harness Wire

ACG Connecto

r

ACG Connecto

r

Oil Level Connectors

Fuel Unit Connectors

Rectifier/Regulator Connecto

r

Pulser Connecto

r

Carburetor Drain Hose

Transmission Case Breather Hose
(MXU 50 REVERSE)

1. GENERAL INFORMATION

1-25

ATV 50

Fuse Box

Start Relay

Tail Light/Brake light Wire

N

egative Cable

Rear Left Turn Signal Light

Rear Right Turn Signal Light Connectors

Positive Cable

Harness Wire

Speed Senso

r

Speedometer Wire

Rear Brake Hose

1. GENERAL INFORMATION

1-26

ATV 50

WIRING DIAGRAM (MX’ER 50) (ON ROAD)

1. GENERAL INFORMATION

1-27

ATV 50

WIRING DIAGRAM (MX’ER 50) (OFF ROAD)

1. GENERAL INFORMATION

1-28

ATV 50

WIRING DIAGRAM (MXU 50) (ON ROAD)

1. GENERAL INFORMATION

1-29

ATV 50

WIRING DIAGRAM (MXU 50 REVERSE) (ON ROAD)

1. GENERAL INFORMATION

1-30

ATV 50

TROUBLESHOOTING

ENGINE WILL NOT START OR IS HARD TO START

c Empty fuel tank
d Clogged float valve
e Clogged charcoal canister
f Clogged fuel filter
g Faulty auto fuel valve

c Faulty spark plug
d Fouled spark plug
e Faulty CDI unit
f Faulty A.C. generator
g Broken or shorted ignition coil
h Broken or shorted exciter coil
iFaulty ignition switch

c Burned or worn cylinder

piston

d Faulty reed valve
e Blown cylinder head gasket
f Leaking crankcase
g Faulty crankcase oil seal

c Incorrectly adjusted idle speed
d Air leaking through intake

pipe

e Incorrect ignition timing

c Flooded carburetor
d Throttle valve excessively

open

c Faulty auto bystarter

Check if fuel reaches
carburetor by loosening
drain screw.

Remove spark plug and
install it into spark plug
cap to test spark by
connecting it to engine
ground.

Inspection/Adjustment

Symptom

Probable Cause

Fuel reaches
carburetor

Spark jumps

Dry spark plug

Not clogged

Normal
compression

Engine does no

t

fire

Fuel does no

t

reach carburetor

Weak or no spark

Wet spark plug

Clogged

Low or no

compression

Engine fires bu

t

does not start

Test cylinde

r

compression.

Remove spark plug and
inspect again.

Wait for 30 minutes and
then remove the carbu­retor auto choke circuit
hose and blow the hose
with mouth.

Start engine by follow­ing normal starting

p

rocedure.

1. GENERAL INFORMATION

1-31

ATV 50

ENGINE STOPS IMMEDIATELY AFTER IT STARTS

c Empty fuel tank
d Clogged float valve
e Clogged charcoal canister
f Clogged fuel filter
g Faulty auto fuel valve

c Fouled spark plug
d Incorrect heat range plug

c Fouled spark plug
d Faulty CDI unit
e Faulty A.C. generator
f Faulty ignition coil
g Broken or shorted high

tension wire

h Faulty ignition switch

c Worn cylinder and piston

rings

d Blown cylinder head gasket
e Flaws in cylinder head
f Faulty reed valve
g Seized piston

c Clogged carburetor jets

c Faulty CDI unit or A.C.

generator

d A.C.G. flywheel not aligned

c Mixture too rich (turn screw

out)

d Mixture too lean (turn screw

in)

Check if fuel reaches
carburetor by loosening
drain screw.

Inspection/Adjustment Symptom

Probable Cause

Fuel reaches
carburetor

Good spark

Remove spark plug and
install it into spark plug
cap to test spark by
connecting it to engine
ground.

Correct timing

Correctly adjusted

Plug not fouled o

r

discolored

Normal
compression

Not Clogged

Fuel does no

t

reach carburetor

Weak or inter-

mittent spark

Incorrect timing

Incorrectly adjusted

Plug fouled o

r

discolored

Abnormal

compression

Clogged

Test cylinde

r

compression (using a
compression gauge).

Check carburetor fo

r

clogging.

Check ignition timing.

Check carburetor ai

r

screw adjustment.

Remove spark plug and
install it into spark plug
cap to test spark by
connecting it to engine
ground.

1. GENERAL INFORMATION

1-32

ATV 50

c Carburetor not securely

tightened

d Faulty intake manifold gasket
e Deformed or broken

carburetor O-ring

c Broken cable
d Dirty auto bystarter
e Faulty auto bystarter

c Faulty auto bystarter

Inspection/Adjustment

Symptom

Probable Cause

No air leak

Not clogged

Clogged

Air leaks

Clogged

Not Clogged

Check carburetor gaske

t

for air leaks.

Connect auto bystarte

r

wire to battery. Wait for
5 minutes, then connect
a hose to fuel enriching
circuit and then blow
the hose with mouth.

Remove auto bystarte

r

connecting wire and
check if bypass fuel
line is clogged.

1. GENERAL INFORMATION

1-33

ATV 50

ENGINE LACKS POWER

c Clogged air cleaner
d Clogged fuel filter
e Clogged exhaust muffler
f Faulty auto bystarter
g Faulty charcoal canister

c Faulty CDI unit
d Faulty A.C. generator

c Worn cylinder and piston

rings

d Blown cylinder head gasket
e Faulty reed valve

c Clogged carburetor jets

c Fouled spark plug
d Incorrect heat range plug

c Mixture too lean
d Poor quality fuel
e Excessive carbon build-up in

combustion chamber

f Ignition timing too early

c Excessive carbon build-up in

combustion chamber

d Poor quality fuel
e Clutch slipping
f Mixture too lean

Inspection/Adjustment Symptom

Probable Cause

Engine speed
increases

Engine overheats

Correct timing

Engine does no

t

knock

Plug not fouled o

r

discolored

Normal
compression

Not Clogged

Engine speed does
not increase
sufficiently

Engine does no

t

overheats

Incorrect timing

Engine knocks

Plug fouled o

r

discolored

Abnormal

compression

Clogged

Start engine and
accelerate lightly for
observation.

Check ignition timing
(using a timing light).

Rapidly accelerate o

r

run at high speed

Test cylinde

r

compression (using a
compression gauge)

Check carburetor fo

r

clogging

Remove spark plug and
inspect

Check if engine
overheats

1. GENERAL INFORMATION

1-34

ATV 50

POOR PERFORMANCE (ESPECIALLY AT IDLE AND LOW SPEEDS)

c Faulty CDI unit
d Faulty A.C. generator

c Mixture too rich (turn screw

out)

d Mixture too lean (turn screw

in)

c Carburetor not securely

tightened

d Faulty intake manifold gasket
e Deformed carburetor O-ring

c Faulty or fouled spark plug
d Faulty CDI unit
e Faulty A.C. generator
f Faulty ignition coil
g Broken or shorted high

tension wire

h Faulty ignition switch

c Broken auto bystarter wire
d Faulty auto bystarter

Inspection/Adjustment Symptom Probable Cause

Clogged

Not clogged

Remove spark plug and
install it into spark plug
cap to test spark by
connecting it to engine
ground.

Check ignition timing.

Connect auto bystarte

r

wire to battery. Wait for
5 minutes, then connect
a hose to fuel enriching
circuit and then blow
the hose with mouth.

Remove auto bystarte

r

connecting wire and
check if bypass fuel
line is clogged.

Check carburetor gaske

t

for air leaks.

Check carburetor ai

r

screw adjustment.

Correct timing

Incorrect timing

Correctly adjusted

Incorrectly adjusted

No air leak

Air leaks

Good spark

Weak or inter-

mittent spark

Not clogged

Clogged

1. GENERAL INFORMATION

1-35

ATV 50

POOR PERFORMANCE (AT HIGH SPEED)

c Faulty CDI unit
d Loose A.C.G. stator
e Faulty A.C. generator

c Empty fuel tank
d Clogged fuel tube or filter
e Clogged charcoal canister

c Clean and unclog

c Broken auto bystarter wire
d Faulty auto bystarter

c Faulty auto bystarter

Inspection/Adjustment Symptom Probable Cause

Clogged

Not clogged

Check ignition timing.

Connect auto bystarte

r

wire to battery. Wait for
5 minutes, then connect
a hose to fuel enriching
circuit and then blow
the hose with mouth.

Remove auto bystarte

r

connecting wire and
check if bypass fuel
line is clogged.

Check carburetor jets
for clogging.

Check auto fuel valve
for fuel supply.

Correct timing

Incorrect timing

Fuel flows freely

Fuel flow restricted

Not clogged

Clogged

Not clogged

Clogged

1. GENERAL INFORMATION

1-36

ATV 50

CLUTCH, DRIVE AND DRIVEN PULLEYS

c Worn or slipping drive belt
d Broken ramp plate
e Broken driven face spring
f Separated clutch lining
g Damaged driven pulley shaft splines
h Damaged final gear
i Seized final gear

c Broken shoe spring
d Clutch outer and clutch weight stuck
eSeized pivot

c Worn or slipping drive belt
d Worn weight rollers
e Seized drive pulley bearings
f Weak driven face spring
g Worn or seized driven pulley bearings

c Worn or slipping drive belt
d Worn weight rollers
e Worn or seized driven pulley bearings

c Oil or grease fouled drive belt
d Worn drive belt
e Weak driven face spring
f Worn or seized driven pulley bearings

STEERING HANDLEBAR DOES NOT TRACK STRAIGHT

(Front and rear tire pressures are normal)

c Steering stem nut too tight
d Broken steering steel balls

c Excessive wheel bearing play
d Bent rim
e Loose axle nut

c Misaligned front and rear wheels
d Bent front fork

Engine starts but motor­cycle does not move

Engine lacks power a

t

start of a grade (poor
slope performance)

Steering is heavy

Front or rear wheel is
wobblin

g

Symptom

Symptom

Probable Cause

Probable Cause

Engine lacks power a

t

high speed

There is abnormal noise
or smell while running

Motorcycle creeps o

r

engine starts but soon
stops or seems to rush
out (Rear wheel rotates
when engine idles)

Steering handlebar pulls
to one side

1. GENERAL INFORMATION

1-37

ATV 50

POOR SUSPENSION PERFORMANCE

(Front and rear tire pressures are normal)

c Weak shock spring
d Excessive load
e Shock damper oil leaking

c Bent fork tube or shock rod
d Fork slider and tube binding

c Fork tube and spring binding
d Fork slider and tube binding

POOR BRAKE PERFORMANCE

(Adjust brake according to standards)

c Worn brake linings
d Worn brake cam contacting area on

brake shoes

e Worn brake cam
f Worn brake drum

c Worn brake linings
d Foreign matter on brake linings
e Rough brake drum contacting area

c Sluggish or elongated brake cables
d Brake shoes improperly contact

brake drum

e Water and mud in brake system
f Oil or grease on brake linings

c Faulty brake master cylinder
d Faulty brake caliper
e Oil or grease on brake disk
f Deformed brake disk
g Leaking brake fluid tube

Suspension is too soft

Brake squeaks

Symptom

Symptom

Probable Cause

Probable Cause

Suspension is too hard

Suspension is noisy

Brake performance is

poor

Index mark on brake

p

anel aligns with wea

r

indicator arrow

Expanding
Brake

Hydraulic
Brake

1. GENERAL INFORMATION

1-38

ATV 50

Faulty

OIL METER

1. Motor oil indicator light does not come on when there is no motor oil (Ignition switch ON)

c Burned out fuse
d Weak or dead battery
e Faulty ignition switch
f Loose or disconnected

connector

g Broken wire harness

cBurned out bulb

c Loose wire connector
d Broken wire harness
e Incorrectly connected wire

c Faulty float
d Broken or shorted wire in

meter

2. Motor oil is sufficient but the indicator light remains on (Ignition switch ON)

c Loose or disconnected

connector

d Broken wire harness
e Incorrectly connected wire

c Faulty float
d Broken or shorted wire in

meter

c Damaged oil tank
d Foreign matters in oil tank

Inspection/Adjustment

Symptom

Inspection/Adjustment

Probable Cause

Symptom Probable Cause

Signals operate
properly

Signals dim, remai

n

on or don‘t operate

Bulb lights

Bulb does not light

Good

Faulty

Remove oil meter and
check operation of
indicator light by
moving float

Check connectors fo

r

p

roper connection.

Good

Good

Faulty

Remove oil meter and
check operation of
indicator light by
moving float

Check connectors for

p

roper operation.

Connect indicator ligh

t

bulb to battery for bulb
ins

p

ection.

Check battery circuit by
operating turn signals.

Good

Faulty

Float up = Light off
Float down = Light on

Float up = Light off
Float down = Light on

1. GENERAL INFORMATION

1-39

ATV 50

FUEL GAUGE

1. Pointer does not register correctly (Ignition switch ON)

c Burned out fuse
d Weak or dead battery
e Faulty ignition switch
f Loose or disconnected

connector

g Broken wire harness

c Faulty float

c Broken or shorted fuel unit

wire

c Loose or disconnected

connector

d Incorrectly connected

connector

c Broken or shorted wire in

fuel gauge

2. Pointer fluctuates or swings (Ignition switch ON)

c Burned out fuse
d Weak or dead battery
e Faulty ignition switch
f Loose or disconnected

connector

g Broken wire harness

c Poor contact in fuel unit

c Insufficient damping oil in

fuel gauge

c Loose or disconnected

connector

c Broken or shorted wire in

fuel gauge

Inspection/Adjustment

Inspection/Adjustment

Symptom

Symptom

Signals operate

prop

erl

y

Signals operate

prop

erl

y

Signals dim, remai

n

on or don‘t operate

Signals dim, remai

n

on or don‘t operate

Pointer does no

t

move

Pointer does no

t

move

Good

Good

Pointer moves

Pointer moves

Pointer moves

Pointer does no

t

move in accord­ance with floa

t

Faulty

Faulty

Pointer does no

t

move

Pointer moves in
accordance with
floa

t

Probable Cause

Probable Cause

Remove fuel unit and
check operation of

p

ointer by moving floa

t

up and down.

Check battery circuit by
operating turn signals.

Check operation of

p

ointer by opening and
shorting fuel unit
terminal on wire
harness side.

Check connectors for

p

roper connection.

Remove fuel unit and
check operation of

p

ointer by moving floa

t

up and down.

Check battery circuit by
operating turn signals
and horn.

Move float up and
down rapidly (1 round
/sec.) to check the
operation of pointer.

Check connectors for

p

roper connection.

1. GENERAL INFORMATION

1-40

ATV 50

STARTER MOTOR

1. Starter motor won‘t turn

c Burned out fuse
d Weak or dead battery
e Faulty stop switch
f Loose or disconnected

connector

g Broken or shorted ignition

switch wire

c Faulty or weak battery

c Poor starter button connection
d Faulty starter relay
e Loose or disconnected

connector

c Faulty starter motor
c Faulty wire harness

2. Starter motor turns slowly or idles

c Weak or dead battery

c Loose or disconnected

connector

d Faulty starter relay

c Seized cylinder
c Broken or shorted starter

motor cable

d Faulty starter pinion

3. Starter motor does not stop turning

c Faulty starter pinion
c Starter relay shorted or stuck

closed

Inspection/Adjustmen

t

Inspection/Adjustmen

t

Inspection/Adjustmen

t

Sympto

m

Sympto

m

Sympto

m

Signals operate
properly

Signals operate

prop

erl

y

Signals dim, remain
on or don‘t o

p

erate

Signals dim, remai

n

on or don‘t operate

Stoplight does no

t

come on

Starter motor turns

Turns easily

Not stopped

Stoplight comes on

Starter does not turn

Hard to turn

Stopped

Relay operates
properly

Starter moto

r

turns slowly

Probable Cause

Probable Cause

Probable Cause

Relay does no

t

operate

Starter moto

r

turns normally

Check operation of
stop switch by
a

pplying

brake.

Check battery circui

t

by operating turn
si

g

nals.

Check battery circui

t

by operating turn
si

g

nals.

Turn ignition switch
OFF.

Check operation of
starter relay by
depressing starter

b

utton.

Connect starte

r

motor directly to
battery.

Connect starte

r

motor directly to
battery.

Rotate crankshaft.

2. FRAME COVERS/EXHAUST MUFFLER

2-0

ATV 50

2

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

FRAME COVERS/EXHAUST MUFFLER

__________________________________________________________________________________

SERVICE INFORMATION------------------------------------------------ 2- 1
TROUBLESHOOTING----------------------------------------------------- 2- 1
FRAME COVERS (MX’ER 50)------------------------------------------- 2- 3
HEADLIGHT REMOVAL (MX’ER 50)--------------------------------- 2- 5
FASTENER REMOVAL -------------------------------------------------- 2- 7
FRAME COVERS (MXU 50 REVERSE/MXU 50)-------------------- 2- 8
EXHAUST MUFFLER REMOVAL (MX’ER 50)---------------------- 2- 15
EXHAUST MUFFLER REMOVAL
(MXU 50 REVERSE/MXU 50) ------------------------------------------- 2- 16

2

2. FRAME COVERS/EXHAUST MUFFLER

2-1

ATV 50

SERVICE INFORMATION

GENERAL INSTRUCTIONS

• When removing frame covers, use special care not to pull them by force because the cover joint
claws may be damaged.

• Make sure to route cables and harnesses according to the Cable & Harness Routing.

TORQUE VALUES

Exhaust muffler lock bolt 3.3 kgf-m (33 N-m, 24 lbf-ft)
Exhaust muffler joint lock nut 1.2 kgf-m (12 N-m, 9 lbf-ft)

TROUBLESHOOTING

Noisy exhaust muffler

• Damaged exhaust muffler

• Exhaust muffler joint air leaks

Lack of power

• Caved exhaust muffler

• Exhaust muffler air leaks

• Clogged exhaust muffler

2. FRAME COVERS/EXHAUST MUFFLER

2-2

ATV 50

MX’ER 50

2. FRAME COVERS/EXHAUST MUFFLER

2-3

ATV 50

FRAME COVERS (MX’ER 50)

SEAT REMOVAL

Pull the lever backward, then pull up the
seat at the rear.
Remove the seat.

LEFT AND RIGHT REAR FENDER
REMOVAL

Remove seven screws and two bolts
attaching the left rear fender.

Remove seven screws and two bolts
attaching the right rear fender.

Remove the left rear fender under bolt.
Remove the left rear fender.

Remove the two bolts under right rear
fender.
Remove the right rear fender.

Sea

t

Screws

Frame Ri

ght

Cove

r

Bol

t

Bol

t

Leve

r

During removal, do not pull the joint
claws forcedly to avoid damage.

＊

Bol

t

Bol

t

2. FRAME COVERS/EXHAUST MUFFLER

2-4

ATV 50

FRONT COVERS REMOVAL

Remove the two screws on the front cover.

Remove the left and right front fender under
bolt.
Remove the front cover.

FRONT FENDER REMOVAL

Remove screws attaching the left and right
front fender.
Remove the left and right front fender.

Bolts

Screws

Front Cove

r

Screws

Right Front Cove

r

Screws

Left Front Cove

r

During removal, be careful not to
damage the joint claws.

＊

2. FRAME COVERS/EXHAUST MUFFLER

2-5

ATV 50

FLOOR BOARD COVER REMOVAL

Remove the four bolts on the floorboard
cover.
Remove the floorboard cover.

HEADLIGHT REMOVAL
(MX’ER 50)

Remove the headlight connector wire.
Remove the two bolts on the headlight.

Bolts

Bol

t

s

Floor Board

2. FRAME COVERS/EXHAUST MUFFLER

2-6

ATV 50

MXU 50 REVERSE/MXU 50

2. FRAME COVERS/EXHAUST MUFFLER

2-7

ATV 50

FASTENER REMOVAL AND
REINSTALLATION

REMOVAL

Depress the head of fastener center piece {.
Pull out the fastener.

INSTALLATION

Let the center piece stick out toward the
head so that the pawls | close.

Insert the fastener into the installation hole.

Push in the head of center piece until it
becomes flush with the fastener outside
face.

To prevent the pawl | from damage,
insert the fastener all the way into the
installation hole

＊

2. FRAME COVERS/EXHAUST MUFFLER

2-8

ATV 50

FRAME COVERS (MXU 50
REVERSE/MXU 50)

SEAT

REMOVAL
Pull the lever (1) backward, then pull up the
seat at the rear.
Remove the seat.

INSTALLATION
To install the seat, align the tabs on the seat

with the grommets on the frame and press
the seat down until it locks.

FRONT CARGO RACK

REMOVAL/INSTALLATION
Remove the two mounting bolts.

Mounting Bolts

2. FRAME COVERS/EXHAUST MUFFLER

2-9

ATV 50

Remove the two mounting bolts from the
front cargo rack right/left side under the
front fender, remove the front cargo rack.

Installation is in the reverse order of
removal.

FRONT CARRIER

REMOVAL/INSTALLATION
Remove front cargo rack (see page 2-8).
Disconnect the right and left signal light

connectors. (ON ROAD)
Remove the bolts from the right/left
headlight case.

Remove the four mounting bolts from the
front carrier right/left side, then remove the
front carrier.

Installation is in the reverse order of
removal.

Mounting Bolts

Bolts

Right/Left Signal Light Connectors

Mounting Bolts

2. FRAME COVERS/EXHAUST MUFFLER

2-10

ATV 50

REAR CARGO RACK

REMOVAL/INSTALLATION
Remove the two bolts under the rear fender.

Remove the two mounting bolts and two
mounting nuts from the rear cargo rack
right/left side under the rear fender.

Installation is in the reverse order of
removal.

RIGHT/LEFT FOOTBOARD

REMOVAL/INSTALLATION

Remove 9 fasteners, 4 mounting bolts and
the right footboard.

Bolts

Mounting Bolts

Mounting Bolts

Fasteners Fasteners

Mounting Nuts

2. FRAME COVERS/EXHAUST MUFFLER

2-11

ATV 50

Remove 9 fasteners, 4 mounting bolts and
the left footboard.

Installation is in the reverse order of
removal.

RIGHT/LEFT SIDE COVER

REMOVAL/INSTALLATION
Open the seat (see page 2-8).
Remove the right/left footboard (see page 2-

10).

Remove the two bolts, fastener and right
side cover.

Remove the two bolts, fastener and left side
cover.

Installation is in the reverse order of
removal.

During removal, do not pull the joint
claws forcedly to avoid damage.

＊

During removal, do not pull the joint
claws forcedly to avoid damage.

＊

Mounting Bolts

Fasteners Fasteners

Fastener Bolts

Bolts Fastene

r

2. FRAME COVERS/EXHAUST MUFFLER

2-12

ATV 50

FRONT CENTER COVER

REMOVAL/INSTALLATION
Remove the front cargo rack (see page 2-8).

Remove the two screws on the front cover,
two screws under the front cover and front
center cover.

Installation is in the reverse order of
removal.

HANDLEBAR COVER

REMOVAL/INSTALLATION
Remove the front center cover (see page 2-

12).

Disconnect the fuel tank breather hose from
the handlebar cover.

Remove the two screws and raise the
handlebar cover.

Disconnect the ignition switch connectors.

Disconnect the instrument connector, then
remove the handlebar cover and instrument.

Installation is in the reserve order of
removal.

During removal, do not pull the joint
claws forcedly to avoid damage.

＊

Screws

Screws

Screws ignition switch connectors

instrument Connectors

Fuel Tank Breather Hose

Push

2. FRAME COVERS/EXHAUST MUFFLER

2-13

ATV 50

FUEL TANK COVER

REMOVAL/INSTALLATION

Remove the four screws and two nuts from
the fuel tank cover.

Remove the fuel tank cap by turning it
counterclockwise and fuel tank seal, then
remove the fuel tank cover.

Installation is in the reverse order of
removal.

MXU 50 REVERSE:

Remove the bolt and then remove the drive
select lever grip.

FRONT FENDER

REMOVAL/INSTALLATION
Remove front carrier (see page 2-9), front

center cover (see page 2-12), fuel tank cover
(see page 2-13) and right/left side cover (see
page 2-10).

Disconnect the right and left headlight
connectors.

Put on the fuel tank cap after removing
the cover to prevent dust, mud, etc. from
entering the fuel tank

＊

Fuel Tank Cap Nuts

Screws Screws

Bol

t

Headlight Connectors

Drive Select Lever Grip

2. FRAME COVERS/EXHAUST MUFFLER

2-14

ATV 50

REAR FENDER

REMOVAL/INSTALLATION
Remove seat(see page 2-8), battery(see page

15-5 ), rear cargo rack (see page 2-10) and
right/left footboard (see page 2-10).

Remove one bolt and one nut, then remove
the oil tank.

Remove the three bolts from the rear fender.

Raise the rear fender and pass the
fuse/battery cables/start relay through out
the rear fender

Disconnect the rear right and left signal
light connectors.

Installation is in the reserve order of
removal.

Bol

t

Nu

t

Bolts

Connecto

r

2. FRAME COVERS/EXHAUST MUFFLER

2-15

ATV 50

EXHAUST MUFFLER (MX’ER

50)

REMOVAL

Remove the two nuts attaching the exhaust
muffler.
Remove the two nuts attaching the exhaust
pipe.

Remove the exhaust muffler lock bolts.
Remove the exhaust muffler and them
remove exhaust pipe.
When installing, first install the exhaust
pipe onto the engine and then install the
exhaust muffler.

Torque:

Exhaust muffler lock bolt:

3.3 kgf-m (33 N-m, 24 lbf-ft)

Exhaust muffler joint lock nut:

1.2 kgf-m (12 N-m, 9 lbf-ft)

Bol

t

Bol

t

Muffle

r

Exhaust Pipe

Gaske

t

Gaske

t

NutsNut

s

Be sure to install a new exhaust muffle

r

gasket.

＊

2. FRAME COVERS/EXHAUST MUFFLER

2-16

ATV 50

EXHAUST MUFFLER (MXU 50
REVERSE/MXU 50)

REMOVAL

Remove the two nuts attaching the exhaust
pipe and cylinder head.

Remove the two bolts attaching the exhaust
muffler, then remove the exhaust muffler.

Inspect the gasket.
If the exhaust gas leaks, the gasket should

be replaced.

Install by reversing the removal sequence.

Torque:

Exhaust muffler lock bolt:

3.3 kgf-m (33 N-m, 24 lbf-ft)

Exhaust muffler joint lock nut:

1.2 kgf-m (12 N-m, 9 lbf-ft)

Bol

t

Bol

t

Nut

s

Gaske

t

Be sure to install a new exhaust gasket.

＊

3. INSPECTION/ADJUSTMENT

3-0

ATV 50

3

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

INSPECTION/ADJUSTMENT

__________________________________________________________________________________

SERVICE INFORMATION------------------------------------------------ 3- 1
MAINTENANCE SCHEDULE-------------------------------------------- 3- 2
FUEL LINE/THROTTLE OPERATION/AIR CLEANER ------------ 3- 3
SPARK PLUG/LUBRICATION SYSTEM------------------------------ 3- 5
CARBURETOR IDLE SPEED -------------------------------------------- 3- 7
CYLINDER COMPRESSION/FINAL REDUCTION GEAR OIL--- 3- 8
DRIVE BELT/BRAKE SHOE/BRAKE SYSTEM --------------------- 3-10
HEADLIGHT AIM---------------------------------------------------------- 3-12
STEERING SYSTEM INSPECTION------------------------------------- 3-13
TOE-IN ADJUSTMENT --------------------------------------------------- 3-14
WHEELS/TIRES ------------------------------------------------------------ 3-15
DRIVE CHAIN SLACK ADJUSTMENT-------------------------------- 3-16
CABLE INSPECTION AND LUBRICATION-------------------------- 3-18
FRONT/REAR SUSPENSION LUBRICATION ----------------------- 3-18

3

3. INSPECTION/ADJUSTMENT

3-1

ATV 50

SERVICE INFORMATION

GENERAL

！ WARNING

•Before running the engine, make sure that the working area is well-ventilated. Never run the
engine in a closed area. The exhaust contains poisonous carbon monoxide gas which may
cause death to people.

•Gasoline is extremely flammable and is explosive under some conditions. The working area
must be well-ventilated and do not smoke or allow flames or sparks near the working area or
fuel storage area.

SPECIFICATIONS

ENGINE
Throttle grip free play : 1～4 mm (0.04 - 0.16 in)
Spark plug gap : 0.6～0.7 mm (0.024 – 0.028 in)
Spark plug: Standard : NGK: BR8HAS

Idle speed : 1800±100rpm
Gear oil capacity (MXU 50/MX’ER 50):
At disassembly : 0.12 liter (0.11 lmp qt, 0.13 Us qt)
At change : 0.09 liter (0.08 lmp qt, 0.1 Us qt)
Gear oil capacity (MXU 50 REVERSE):
At disassembly : 0.3 liter (0.26 lmp qt, 0.32 Us qt)
At change : 0.25 liter (0.22 lmp qt, 0.26 Us qt)
Cylinder compression: 1200 kPa (12 kgf/cm²,170 psi)
Ignition timing:
MXU 50/MX’ER 50: BTDC 22°/2000rpm
MXU 50 REVERSE: BTDC 13.5°/1500rpm

CHASSIS
Front brake free play: 10～20 mm (0.4 – 0.8 in)
Rear brake free play: 10～20 mm (0.4 – 0.8 in)

TIRE PRESSURE

MX’ER 50 (1 Rider) MXU 50 REVERSEMXU 50 (1 Rider)

Front 33 kPa (0.33 kgf/cm², 4.7 psi) 28 kPa (0.28 kgf/cm², 3.9 psi)

Rear 33 kPa (0.33 kgf/cm², 4.7 psi) 28 kPa (0.28 kgf/cm², 3.9 psi)

TIRE SIZE:
MX’ER 50:

Front: 20*7-8
Rear : 22*10-8

MXU 50 REVERSE/MXU 50

Front: 21*7-10
Rear : 22*10-10

3. INSPECTION/ADJUSTMENT

3-2

ATV 50

TORQUE VALUES

Front wheel nut 70 N-m (7 kgf-m, 50 lbf-ft)
Rear wheel nut 70 N-m (7 kgf-m, 50 lbf-ft)

MAINTENANCE SCHEDULE

This chapter includes all information necessary to perform recommended inspections and
adjustments. These preventive maintenance procedures, if followed, will ensure more reliable
vehicle operation and a longer service life. The need for costly overhaul work will be greatly
reduced. This information applies to vehicles already in service as well as new vehicles that are
being prepared for sale. All service technicians should be familiar with this entire chapter.

• In the interest of safety, we recommend these items should be serviced only by an authorized
KYMCO motorcycle dealer.

3. INSPECTION/ADJUSTMENT

3-3

ATV 50

FUEL LINE

Check the fuel tubes and replace any parts,
which show signs of deterioration, damage
or leakage.

THROTTLE OPERATION

Check the throttle to swing for smooth
movement.
Measure the throttle to swing free play.

Free Play: 1～4 mm (0.04 - 0.16 in)

Minor adjustment is made with the
adjusting nut at the throttle to swing above.
Slide the rubber cover out and adjust by
loosening the lock nut and turning the
adjusting nut.

AIR CLEANER

AIR CLEANER REPLACEMENT

Remove five screws on the air cleaner case
cover and the cover.

Check the element and replace it if it is
excessively dirty or damaged.

Do not smoke or allow flames or sparks
in your working area.

＊

Lock Nu

t

Adjusting Nu

t

Fuel Filte

r

Fuel tube

Screws

Air Cleaner Case Cove

r

3. INSPECTION/ADJUSTMENT

3-4

ATV 50

CLEAN AIR FILTER ELEMENT

Wash the element gently, but thoroughly in
solvent.

Squeeze the excess solvent out of the
element and let dry.

Apply the engine oil.
Squeeze out the excess oil.

CHANGE INTERVAL

More frequent replacement is required when
riding in unusually dusty or rainy areas.

Use parts cleaning solvent only. Neve

r

use gasoline or low flash point solvents
which may lead to a fire or explosion.

＊

Air Cleaner Elemen

t

Do not twist or wring out the foa

m

element. This could damage the foam
material.

＊

The element should be wet but not
dripping.

＊

3. INSPECTION/ADJUSTMENT

3-5

ATV 50

Gap, Wear, and Fouling Deposits

SPARK PLUG

Remove the spark plug
Check the spark plug for wear and fouling
deposits.
Clean any fouling deposits with a spark
plug
cleaner or a wire brush.
Specified Spark Plug: NGK-BR8HAS

Measure the spark plug gap.
Spark Plug Gap:

0.6～0.7 mm (0.024 – 0.028)

LUBRICATION SYSTEM

《Oil Filter Cleaning》
Disconnect the oil tube at the oil pump side
and allow oil to drain into a clean container.
Remove the tube clip at the oil tank side and
disconnect the oil tube.

Remove the oil filter.

Cracks, Damage

Washer Deformation

When installing, first screw in the spar

k

plug by hand and then tighten it with a
spark plug wrench.

＊

Clip

Oil Filte

r

3. INSPECTION/ADJUSTMENT

3-6

ATV 50

Clean the oil filter screen with compressed
air.

Install the oil filter in the reverse order of
removal and fill the oil tank with specified
oil up to the proper level.

Bleed air from the oil pump and oil lines.

《Oil Pump Condition》

Open the throttle valve fully and check that
the index mark on the pump body aligns
with the aligning mark on the oil pump

control lever.
Reference tip alignment within 1mm of

index mark on open side is acceptable.
Start and idle the engine, then slowly open

the throttle to increase engine rpm and
check the operation of the oil pump control

lever.
If adjustment is necessary, adjust the oil
pump control cable by loosening the control

cable lock nut and turning the adjusting nut.
After adjustment, tighten the lock nut.

If the oil pump is not synchronized
properly,
the following will occur:

• Excessive white smoke or hard starting

due to pump control lever excessively open

• Seized piston due to pump control lever

insufficiently open.

Control Aligning Mark

Filter Screen

Adjusting Nu

t

• Connect the oil tubes securely.

• Install the tube clip at the oil tank side

and also install the clip to the lower oil
tube that goes to the oil pump.

• Check for oil leaks.

＊

Adjust oil pump control cable after the
throttle grip free play is adjusted.

＊

Reference tip alignment within 1mm of
index mark on open side is acceptable.
However, the aligning mark on the
control lever must never be on the
closed side of the index mark, otherwise
engine damage will occur because of
insufficient lubrication.

＊

Lock Nu

t

3. INSPECTION/ADJUSTMENT

3-7

ATV 50

CARBURETOR IDLE SPEED

Warm up the engine before this operation.
Start the engine and connect a tachometer.
Turn the throttle stop screw to obtain the
specified idle speed.

Idle Speed: 1800±100 rpm
When the engine misses or run erratic,

adjust the air screw.

《Ignition Apparatus》

Remove the A.C. generator fan cover.
(Ö8-3)

Remove the four bolts attaching the fan and
then remove the fan.

Warm up the engine and check the ignition
timing with a timing light.

When the engine is running at the specified
rpm, the ignition timing is correct if the “F”
mark on the flywheel aligns with the index
mark on the crankcase within ±1.5°.

Ignition Timing:
MX’ER 50: 22°±1.5°BTDC/2000rpm
MXU 50 REVERSE/MXU 50:

13.5°±1.5°BTDC/1500rpm

Throttle Stop Screw

AirScrew

Bolts

Index Mark

“F” Mark

• The engine must be warm for accurate
idle speed inspection and adjustment.

＊

The CDI ignition timing is not adjust­able. If the timing is incorrect, check
the CDI unit, ignition coil and A.C.
generator and replace any faulty parts.

＊

3. INSPECTION/ADJUSTMENT

3-8

ATV 50

CYLINDER COMPRESSION

Warm up the engine before compression
test.
Remove the spark plug.
Insert a compression gauge.
Open the throttle valve fully and push the
starter button to test the compression.

Compression:

1200kPa (12kgf/cm²,170psi)

If the compression is low, check for the
following:

- Leaky valves

- Valve clearance too small

- Leaking cylinder head gasket

- Worn piston rings

- Worn piston/cylinder
If the compression is high, it indicates that

carbon deposits have accumulated on the
combustion chamber and the piston head.

FINAL REDUCTION GEAR OIL

MXU 50/MX’ER 50: Gear Oil Lever

The gear oil level shall be at the oil check
bolt hole. If the oil level is low, add the
specified oil to the proper level.
Specified Gear Oil: SAE10W90#

Install and tighten the oil check bolt.
Torque: 1.3 kgf-m (13 N-m, 9.4 lbf-ft)
Start the engine and check for oil leaks.

Compression Gauge

Oil Check Bol

t

MXU 50/MX’ER 50

3. INSPECTION/ADJUSTMENT

3-9

ATV 50

GEAR OIL CHANGE

Remove the oil filler bolt.
Removes the oil drains bolt and drain the oil
thoroughly.
Install the oil drain bolt.
Torque: 1.3 kgf-m (13 N-m, 9.4 lbf-ft)

Fill with the recommended oil.

Specified Gear Oil: SAE10W90#
Oil Capacity:

MXU 50/MX’ER 50
At disassembly:

0.12 liter (0.11 lmp qt,0.13 Us qt)

At change: 0.09 liter (0.08 lmp qt,0.1 Us qt)

MXU 50 REVERSE
At disassembly:

0.3 liter (0.26 lmp qt,0.32 Us qt)

At change:

0.25 liter (0.22 lmp qt,0.26 Us qt)

Reinstall the oil filler bolt and check for oil
leaks.
Torque: 1.3 kgf-m (13N-m, 9.4 lbf-ft)

Oil Drain Bolt/ Sealing Washe

r

Oil Filler Bol

t

MXU 50/MX’ER 50

Oil Drain Bolt/ Sealing Washe

r

MXU 50 REVERSE

Oil Fille

r

Bol

t

Make sure that the sealing washer is in
good condition.

＊

3. INSPECTION/ADJUSTMENT

3-10

ATV 50

DRIVE BELT

Remove the left crankcase cover.
Inspect the drive belt for cracks, scaling,
chipping or excessive wear.
Measure the V-belt width

Service limit: 16.5mm (0.7 in)
Replace the drive belt if out of specification.

BRAKE SHOE

Replace the brake shoes if the arrow on the
wear indicator plate aligns with the punch
mark on the brake panel when the brake is
fully applied.

BRAKE SYSTEM

FRONT BRAKE

Measure the front brake lever free play.
Free Play: 10～20 mm (0.4 – 0.8 in)
Adjust if out of specification.

Wear Indicato

r

Punch Mark

Drive Bel

t

3. INSPECTION/ADJUSTMENT

3-11

ATV 50

Adjust brake lever free play:
Loosen the lock nuts.
Turn the adjusters in or out until the

specified free play is obtained.
Turning adjusters in that the free play is

increased.
Turning adjusters out that the free play is

decreased.

The difference between both clearances
should be 2 mm (0.08 in)or less when front
brake is applied.

Tighten the lock nuts.

REAR BRAKE (drum brake)

Measure the rear brake lever free play.
Free Play: 10～20 mm (0.4 – 0.8 in)

If the free play do not fall within the limit,
adjust by turning the adjusting nut.

Adjusting Nu

t

Lock Nuts

Ad

j

usters

Make sure that the brake does not drag
after adjusting.

＊

3. INSPECTION/ADJUSTMENT

3-12

ATV 50

HEADLIGHT AIM

MX’ER 50:

Turn the ignition switch ON and start the
engine.
Turn on the headlight switch.

Adjust the headlight aim by turning the
headlight aim adjusting screw.

MXU 50 REVERSE/MXU 50:

Turn the ignition switch ON and start the
engine.
Turn on the headlight switch.
Adjust the headlight aim by turning the
headlight aim adjusting screws.

Adjusting Screw

Adjust Screws

3. INSPECTION/ADJUSTMENT

3-13

ATV 50

STEERING SYSTEM
INSPECTION

Place the machine on a level place.
Check the steering column bushings and

bearings:
Move the handlebar up and down, and/or

back and forth.
Replace the steering column bushings and

or bearings if excessive play

Check the tie-rod ends
Turn the handlebar to the left and/or right

until it stops completely, then slightly move
the handlebar from left to right.

Replace the tie-rod ends if tie-rod end has
any vertical play.

Raise the front end of the machine so that
there is no weight on the front wheels.

Check ball joints and/or wheel bearings.
Move the wheels lately back and forth.
Replace the front arms and/or wheel

bearings if excessive free play.

Tie-rod Ends

3. INSPECTION/ADJUSTMENT

3-14

ATV 50

TOE-IN ADJUSTMENT

Place the machine on a level place.
Measure the toe-in
Adjust if out of specification.
Toe-in measurement steps:
Mark both front tire tread centers.
Raise the front end of the machine so that

there is no weight on the front tires.
Fix the handlebar straight ahead.
Measure the width A between the marks.
Rotate the front tires 180 degrees until the

marks come exactly opposite.
Measure the width B between the marks.
Calculate the toe-in using the formula given

below.
Toe-in = B－A
Toe-in: 0～10mm ( 0 – 0.4 in)
If the toe-in is incorrect, adjust the toe-in

Adjust the toe-in step:

Mark both tie-rods ends.
This reference point will be needed during
adjustment.
Loosen the lock nuts (tie-rod end) of both
tie-rods
The same number of turns should be given
to both tie-rods right and left until the
specified toe-in is obtained, so that the
lengths of the rods will be kept the same.

Torque: 3 kgf-m (30 N-m, 22 lbf-ft)

• Be sure that both tie-rod are turned the
same amount. If not, the machine will
drift tight or left even though the
handlebar is positioned straight which
may lead to mishandling and accident.

• After setting the toe-in to specification,
run the machine slowly for some
distance with hands placed lightly on
the handlebar and check that the
handlebar responds correctly. If not,
turn either the right or left tie-rod
within the toe-in specification.

＊

A

B

Tie-rod

Tie-rod End Nuts

3. INSPECTION/ADJUSTMENT

3-15

ATV 50

WHEELS/TIRES

Check the tires for cuts, imbedded nails or
other damages.
Check the tire pressure.

TIRE PRESSURE

Front/Rear (1 Rider)

MX’ER 50 0.33 kgf/cm² (33 kPa, 4.7 psi)
MXU 50 0.28 kgf/cm² (28 kPa, 3.9 psi)

TIRE SIZE
MXU 50 REVERSE/MXU50:
Front: 21*7-10
Rear: 22*10-10

MX’ER 50:
Front: 20*7-8
Rear: 22*10-8

Check the front axle nut for looseness.
Check the rear axle nut for looseness.
If the axle nuts are loose, tighten them to the
specified torque.

Torque:
Front : 7 kgf-m (70 N-m, 50 lbf-ft)
Rear : 7 kgf-m (70 N-m, 50 lbf-ft)

WHEEL INSPECTION

Inspect the tire surfaces.
Replace if wear or damage.
Tire wear limit: 3 mm (0.1 in)

Front Axle Nu

t

Tire pressure should be checked when
tires are cold.

＊

RearAxle Nu

t

It is dangerous to ride with a worn out
tire. When a tire wear is out of
specification, replace the tire
immediately.

＊

3. INSPECTION/ADJUSTMENT

3-16

ATV 50

Inspect the wheel.
Replace if damage or bends
Always balance the wheel when a tire or

wheel has been changed or replaced.

DRIVE CHAIN SLACK
ADJUSTMENT

Before checking and/or adjusting, rotate the
rear wheels several revolutions and check
slack at several points to find the tightest
point. Check and/or adjust the chain slack
with the rear wheels in this “tightest”
position.

Place the machine on a level place.

Check drive chain slack.
Adjust if out of specification.
Drive chain slack: 10-20 mm (0.4 – 0.8 in)

Adjust drive chain slack:
Elevate the rear wheels by placing a suitable

stand under the rear of frame.

Loosen four bolts attaching rear axle hub.

• Never attempt even small repairs to the
wheel.

• Ride conservatively after installing a
tire to allow it to seat itself properly on
the rim.

＊

Too little of chain slack will overload the
engine and other vital parts; keep the

＊

Wheels should be on the ground without

＊

Support the machine securely so there is

＊

Bolts

3. INSPECTION/ADJUSTMENT

3-17

ATV 50

Turn the adjuster in or out until the
specified slack is obtained.

Turn in: Slack is increased.
Turn out: Slack is decreased.

Tighten four bolts attaching rear axle hub to
the specification. While pushing up or down
on the chain to zero slack.

Torque: 7 kgf-m (70 N-m, 50 lbf-ft)

Tighten the adjuster.
Torque: 2.2 kgf-m (22 N-m, 16 lbf-ft)

Adjuste

r

Adjuste

r

Bolts

3. INSPECTION/ADJUSTMENT

3-18

ATV 50

CABLE INSPECTION AND
LUBRICATION

Inspect the cable sheath.
Replace if damage.
Check the cable operation.
Lubricate or replace if unsmooth operation.

LEVER LUBRICATION

Lubricate the pivoting parts of each lever.

FRONT/REAR SUSPENSION
LUBRICATION

Inject grease into the nipples using a grease
gun until slight over flow is observed from
the thrust covers.

N

ipple

Damaged cable sheath may cause
corrosion and interfere with the cable
movement. An unsafe condition may
result so replace such cable as soon as
possible.

＊

Wipe off the excess grease.

＊

Hold cable end high and apply several
drops of lubricant to cable.

＊

4. LUBRICATION SYSTEM

4-0

ATV 50

4

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

LUBRICATION SYSTEM

__________________________________________________________________________________

SERVICE INFORMATION ................................................................ 4-2

TROUBLESHOOTING ....................................................................... 4-2

OIL PUMP REMOVAL....................................................................... 4-3

OIL PUMP INSPECTION................................................................... 4-3

OIL PUMP INSTALLATION ............................................................. 4-4

OIL PUMP BLEEDING....................................................................... 4-5

OIL TANK ........................................................................................... 4-6

4

4. LUBRICATION SYSTEM

4-1

ATV 50

LUBRICATION SYSTEM

4. LUBRICATION SYSTEM

4-2

ATV 50

SERVICE INFORMATION

GENERAL INSTRUCTIONS

• Use care when removing and installing the oil pump not to allow dust and dirt to enter the engine
and oil line.

• Do not attempt to disassemble the oil pump.

• Bleed air from the oil pump if there is air between the oil pump and oil line.

• If the oil is disconnected, refill the oil line with motor oil before connecting it.

SPECIFICATIONS

• Recommended Motor Oil: SAE20W20# 2-stroke Motor Oil

• Oil Capacity : 1 liter (0.88 lmp qt, 1.06 Us qt)

Light comes on : 0.25 liter (0.22 lmp qt, 0.27 Us qt)

TROUBLESHOOTING

Excessive white smoke or carbon deposits on spark plug

• Oil pump not properly synchronized (excessive oil)

• Poor quality oil

Engine overheating

• Oil pump not properly adjusted (insufficient oiling)

• Poor quality oil

Seized piston

• No oil in tank or clogged oil line

• Oil pump not properly adjusted (insufficient oiling)

• Air in oil line

• Faulty oil pump

Oil not flowing out of tank to engine

• Clogged oil tank cap breather hole

• Clogged oil filter

4. LUBRICATION SYSTEM

4-3

ATV 50

OIL PUMP REMOVAL

Disconnect the oil pump control cable from
the pump body.
Disconnect the oil inlet line from the oil
pump.
Then, disconnect the oil outlet line.

Remove the oil pump control cable plate
bolt.
Remove the oil pump from the crankcase.

OIL PUMP INSPECTION

Remove the oil pump and inspect the
following items:

• Weakened O-ring

• Damage to crankcase mating surface

• Damage to pump body

• Control lever operation

• Oil leaks through oil seals

• Worn or damaged pump pinion

Do not allow foreign matters to enter the
crankcase. Before removing the oil
pump, clean the oil pump and crankcase
surfaces.

＊

Oil Outlet Line

Oil Inlet Line

Control Cable

Oil Pump

Control Cable plate

O-ring

Gea

r

Control Leve

r

Do not disassemble the oil pump which
cannot be used after disassembly.

＊

Before disconnecting the oil line, clip
the oil line to avoid oil flowing out and
then plug the oil line after it is
disconnected.

＊

Bol

t

4. LUBRICATION SYSTEM

4-4

ATV 50

Oil Pump Driven Gea

r

Bolts

Nut

OIL PUMP INSTALLATION

Install the oil pump onto the crankcase.

Install the oil pump control cable plate.
Connect the oil inlet line and oil outlet line
properly.
Connect the oil pump control cable.
Bleed air from the oil pump.

• Lubricate the O-ring with grease or
engine oil before installation.

• Make sure that the oil pump is inserted
into the crankcase.

• Apply molybdenum disulfide or
grease to the pump pinion.

＊

Grease or Engine Oil

Control Cable

Oil Outlet Line

Oil Inlet Line

4. LUBRICATION SYSTEM

4-5

ATV 50

OIL PUMP BLEEDING

OIL INLET LINE/OIL PUMP BLEEDING

Fill the oil tank with recommended oil.
Place a shop towel around the oil pump.
Disconnect the oil inlet line from the oil
pump and clip it.
Fill the oil pump with oil by squirting clean
oil through the joint. (About 3cc, 0.003 lmp
qt, 0.003 Us qt)
Fill the oil line with oil and connect it to the
oil pump.

OIL OUTLET LINE BLEEDING

1. Disconnect the oil outlet line and bend it
into U shape. Force air out of the tube
by filling it with oil.

2. Start the engine and allow it to idle with
the oil control lever in the fully open
position. Visually check the oil flow.

3. If there is no oil flowing out within 1
minute, bleed air from the oil inlet line
and oil pump.

Oil Outlet Line

• Air in the oil lines will block oil flow

and result in severe engine damage.

• Bleed air from the oil lines and oil

pump whenever the oil lines or pump
have been removed or there is air in
the oil lines.

＊

Bleed air from the oil inlet line first,
then bleed air from the oil outlet line.

＊

• Never run the engine in a closed area.

• Do not increase the engine speed at

will.

＊

Oil Pump

Oil Outlet Line

4. LUBRICATION SYSTEM

4-6

ATV 50

Pump Cove

r

Dowel Pin

OIL TANK

OIL TANK REMOVAL

Remove the seat. (Ö2-3 or 2-8)
Remove the oil meter connector.
Remove the one bolt and one nut from the
oil tank. (see page 2-14)
Disconnect the oil inlet line.
Drain the oil inside the oil tank into a clean
container.
Remove the oil tank.
The installation sequence is the reverse of
removal.

• Connect the oil line properly.

• Bleed air from the oil pump after

installation.

• The oil tube clip (at the oil tank side)
must be locked from inside of the oil
tube joint.

＊

Wire Connecto

r

5. FUEL SYSTEM

5-0

ATV 50

5

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

FUEL SYSTEM

__________________________________________________________________________________

SERVICE INFORMATION------------------------------------------------ 5- 2
TROUBLESHOOTING----------------------------------------------------- 5- 2
THROTTLE VALVE DISASSEMBLY/CARBURETOR REMOVAL-- 5- 3
AUTO BYSTARTER ------------------------------------------------------- 5- 6
FLOAT/FLOAT VALVE/JETS/FLOAT CHAMBER------------------ 5- 8
CARURETOR INSTALLATION ----------------------------------------- 5-11
AIR SCREW ADJUSTMENT --------------------------------------------- 5-12
REED VALVE --------------------------------------------------------------- 5-13
FUEL TANK ----------------------------------------------------------------- 5-14
FUEL VALVE REMOVAL------------------------------------------------ 5-15
AIR CLEANER -------------------------------------------------------------- 5-15

5

5. FUEL SYSTEM

5-1

ATV 50

5. FUEL SYSTEM

5-2

ATV 50

SERVICE INFORMATION

GENERAL INSTRUCTIONS

•When working with gasoline, keep away from sparks and flames..

•Note the locations of O-rings when disassembling and replace them with new ones during

assembly.

•All cables, fuel lines and wires must be routed and secured at correct locations.

•Bleed air from the oil lines whenever they are disconnected.

SPECIFICATIONS

ATV 50
Venturi dia. 14 mm (0.56 in)
Identification number PB
Float level 8.6 mm (0.34 in)
Main jet # 80
Slow jet # 38S
Air screw opening 2 ± 1/2
Idle speed 1800±100 rpm
Throttle grip free play 1～4 mm (0.04 – 0.16 in)

SPECIAL TOOL

Float level gauge

TROUBLESHOOTING

Engine does not start Lean mixture

• No fuel in tank • Clogged fuel jets • Faulty float valve

• Too much fuel getting to cylinder • Clogged fuel cap vent • Float level too low

• Clogged fuel filter • Clogged fuel filter • Clogged air cleaner

• Clogged air cleaner • Bent, kinked or restricted fuel line

Engine idles roughly, stalls or runs poorly Rich mixture

• Incorrect idle speed • Clogged air cleaner • Faulty float valve

• Ignition malfunction • Intake air leaks • Float level too high

• Compression too low • Fuel contaminated • Clogged air jets

• Incorrectly adjusted air screw • Faulty reed valve

• Incorrect float level • Clogged fuel jets

5. FUEL SYSTEM

5-3

ATV 50

THROTTLE VALVE DIS­ASSEMBLY/CARBURETOR
REMOVAL

Loosen the carburetor cap and remove the
throttle valve.

Disconnect the throttle cable from the
throttle valve.

Remove the throttle valve spring, carburetor
cap and rubber seal.

Carburetor Cap

Throttle Valve

Rubber Seal

Carburetor Cap

Spring

5. FUEL SYSTEM

5-4

ATV 50

Remove the jet needle by removing the
needle clip.
Check the jet needle and throttle valve for
wear or damage.

THROTTLE VALVE INSTALLA-TION

Install the jet needle on the throttle valve and
secure with the needle clip.

Install the rubber seal on the throttle cable
and then install the carburetor cap and
throttle valve spring.

Connect the throttle cable to the throttle
valve.

N

eedle Retaine

r

2nd Notch (STD)

Throttle Valve

Jet Needle

Needle Clip

Carburetor Cap

Rubber Seal

Throttle Valve Spring

Throttle Valve

Throttle Cable

5. FUEL SYSTEM

5-5

ATV 50

Install the throttle valve by aligning the
groove in the throttle valve with the throttle
stop screw.

Tighten the carburetor cap.
After installation, perform the following
adjustments and inspections.

• Throttle cable free play (Ö3-3)

• Idle speed adjustment (Ö3-7)

CARBURETOR REMOVAL

Remove the air cleaner by removing the air
cleaner band screw and attaching bolts.
Disconnect the fuel tube.
Loosen the drain bolt to drain fuel from the
carburetor.
Disconnect the auto bystarter wire
connector.

Groove

Carburetor Cap

Drain Bol

t

Throttle Cable

Fuel Tube

Band

Bystarte

r

5. FUEL SYSTEM

5-6

ATV 50

Remove the two carburetor lock nuts.
Remove the carburetor.

AUTO BYSTARTER

AUTO BYSTARTER INSPECTION

Measure the resistance between the auto
bystarter wire terminals.
Resistance:5Ω (10 minutes minimum after

stopping the engine)

If the resistance exceeds 5Ω, replace the auto
bystarter with a new one.

After the engine stops for 30 minutes,
connect a hose to the fuel enriching circuit
and blow the hose with mouth.
If air cannot be blown into the hose
(clogged), the auto bystarter is faulty.
Replace it with a new one.

Nut

s

5. FUEL SYSTEM

5-7

ATV 50

Connect the auto bystarter yellow wire to the
battery positive (+) terminal and green/ black
wire to the battery negative (-) terminal and
wait 5 minutes.
Connect a hose to the fuel enriching circuit
and blow the hose with mouth.
If air can be blown into the hose, the auto
bystarter is faulty and replace it with a new
one.

AUTO BYSTARTER REMOVAL

Remove the auto bystarter cover.
Remove the two auto bystarter set plate
screws to remove the auto bystarter.

Check the auto bystarter valve and needle for
wear or damage.
Check the O-ring for wear or damage.

Auto Bystarte

r

Screws

O-ring

Set Plate

Bystarter Valve

Bystarter Needle

5. FUEL SYSTEM

5-8

ATV 50

AUTO BYSTARTER INSTALLATION

Install the auto bystarter into the carburetor
body until it bottoms..
Install the set plate and then tighten the two
screws.

FLOAT/FLOAT VALVE/JETS
FLOAT CHAMBER

Remove the two float chamber screws and
the float chamber.

Remove the screw and O-ring.
Remove the float pin, float and float valve.

Auto Bystarte

r

Floa

t

O-ring

Set Plate

Float Pin

Screws

Screws

5. FUEL SYSTEM

5-9

ATV 50

FLOAT/FLOAT VALVE INSPECTION

Inspect the float for damage or fuel inside
the float.
Check the float valve seat for wear or
damage.

JETS/SCREWS REMOVAL

Before removing the throttle stop screw or
air screw, record the number of rotations
until it seats lightly. Then, remove them.

Remove the main jet and needle jet holder.

CARBURETOR PASSAGES CLEANING

Blow compressed air through all passages of
the carburetor body with an air gun.

Float Valve

Float Sea

t

Main Je

t

Throttle Stop Screw

Air Screw

Do not force the air screw against its
seat to prevent damage.

＊

5. FUEL SYSTEM

5-10

ATV 50

FLOAT CHAMBER ASSEMBLY

Install the main jet and needle jet holder.
Install the air screw and throttle stop screw

according to the rotations recorded.

Install the float valve, float and float pin.
Tighten the float screw securely.

FLOAT LEVEL INSPECTION

Slightly tilt the carburetor and measure the
float level with the float valve just
connecting the float arm.

Float Level: 8.6 mm (0.34 in)
Replace the float if the level is out of the

specified level range.
Install the O-ring.
Check the operation of the float and install
the float chamber.
Tighten the screws.

Air Screw

Throttle Stop Screw

N

eedle Jet holde

r

Float Pin

Main Je

t

If the air screw must be replaced, be
sure to perform the air screw adjustment
again.

＊

5. FUEL SYSTEM

5-11

ATV 50

CARBURETOR INSTALLATION

Check the carburetor insulator and O-ring
for wear or damage.

Install the carburetor and insulator onto the
intake manifold and tighten the two lock
nuts.

Connect the fuel tube and auto bystarter wire
connector.

Install the carburetor cap. (Ö5-3)
Install the fuel tube
Install the air cleaner onto the carburetor and
tighten the band screw.

O-rings

Insulato

r

N

uts

When installation, do not allow foreign
particles to enter the carburetor.

＊

Route the auto bystarter wire correctly
and properly.

＊

Fuel TubeCarburetor Cap

Band

5. FUEL SYSTEM

5-12

ATV 50

AIR SCREW ADJUSTMENT

Turn the air screw clockwise until it seats
lightly and back it to the specification given.

Start the engine and turn the air screw in or
out slowly to obtain the highest engine
speed.

Turn the throttle stop screw to obtain the
specified idle speed.

Idle Speed: 1800±100 rpm
Air Screw Opening: 2 ± 1/2 turns

Slightly increase the engine speed and make
sure that the engine does not miss or run
erratic.

If the adjustment of the air screw within the
range of ±1/2 turn makes no difference to the
engine performance, check other related
items.

Air Screw

Throttle Stop Screw

Do not force the air screw against its
seat to prevent damage.

＊

5. FUEL SYSTEM

5-13

ATV 50

REED VALVE

REMOVAL

Remove the four intake manifold bolts and
gasket.
Remove the reed valve and gasket.

INSPECTION

Check the reed valve for damaged or weak
reeds.
Check the reed valve seat for cracks, damage
or clearance between the seat and reed.
Replace the valve if necessary.

INSTALLATION

Install the reed valve in the reverse order of
removal.

Bolts

Reeds

Intake Manifold

Reed Valve Sea

t

Reed Stoppe

r

Do not disassemble or bend the ree

d

stopper. To do so can cause loss of
engine power and engine damage. If any
of the stopper, reed or valve seat is
faulty, replace them as unit.

＊

Install a new gasket with the gasket
indentation aligned with the reed valve.
After installation, check for intake air
leaks.

＊