KEEWAY QJ50T-21U Maintenance Manual

Motorcycle QJ50T-21U

Maintenance Manual

Qianjiang Motor Corporation Ltd.

Contents

Contents ....................................................................................................................................................................... 2

Preface ......................................................................................................................................................................... 5

Preparing Documents........................................................................................................................................... 6

Inspection/Adjustment ....................................................................................................................................... 38

Inspection and Maintenance of Electrical System ..................................................................................................... 51

I. Battery/Charging System........................................................................................................................................ 54

1.1 Preparing Documents ................................................................................................................................... 54

1.2 Failure diagnosis .......................................................................................................................................... 55

1.3 Battery ......................................................................................................................................................... 56

1.4 Charging System .......................................................................................................................................... 57

1.5 Voltage/Current Regulator ........................................................................................................................... 58

1.6 Magnetor charging coil ................................................................................................................................ 59

1.7 Magnetor Lighting Coil ............................................................................................................................... 59

II. Ignition System ..................................................................................................................................................... 62

2.1 Preparing Documents ................................................................................................................................... 62

2.2 Failure Diagnosis ......................................................................................................................................... 63

2.3 Ignition System Check ................................................................................................................................. 64

2.4 CDI Group ................................................................................................................................................... 65

2.5 Ignition Coil ................................................................................................................................................. 66

2.6 Trigger ......................................................................................................................................................... 67

III. Startup System ..................................................................................................................................................... 69

3.1 Preparing documents ................................................................................................................................... 69

3.2 Failure diagnosis .......................................................................................................................................... 70

3.3 Startup Motor ............................................................................................................................................... 70

3.4 Starter Relay ................................................................................................................................................ 72

IV. Bulbs/Switches/Meters ........................................................................................................................................ 75

4.1 Preparing documents ................................................................................................................................... 75

4.2 Failure Diagnosis ......................................................................................................................................... 75

4.3 Replacement of Headlamp Bulbs ................................................................................................................ 75

4.4 Replacement of front steering lamp bulbs ................................................................................................... 76

4.5 Replacement of tail lamp bulbs ................................................................................................................... 76

4.6 Meter ............................................................................................................................................................ 77

4.7 Main Switch ................................................................................................................................................. 77

4.8 Horn ............................................................................................................................................................. 78

4.9 Handlebar Switch......................................................................................................................................... 78

Inspection and Maintenance of the Chassis ............................................................................................................... 79

5. Brake ...................................................................................................................................................................... 82

5.1 Maintenance Instruction .............................................................................................................................. 82

5.2 Failure Diagnosis ......................................................................................................................................... 82

5.3 Front Disc Brake .......................................................................................................................................... 83

5.4 Rear Drum Brake ......................................................................................................................................... 85

6. Body ...................................................................................................................................................................... 88

7. Front Wheel / Front Suspension ............................................................................................................................ 92

7.1 Preparing Documents ................................................................................................................................... 92

7.2 Failure Diagnosis ......................................................................................................................................... 92

7.3 Front Wheel ................................................................................................................................................. 93

7.4 Steering Handle ........................................................................................................................................... 95

7.5 Front Fork .................................................................................................................................................... 96

8. Rear Wheel/Rear Suspension............................................................................................................................... 100

8.1 Preparing Documents ................................................................................................................................. 100

8.2 Failure Diagnosis ....................................................................................................................................... 100

8.3 Rear Wheel ................................................................................................................................................ 101

8.4 Rear Absorber ............................................................................................................................................ 102

9.Fuel Tank/Seat ...................................................................................................................................................... 106

9.1 Preparing Documents ................................................................................................................................. 106

9.29.2 Failure Diagnosis .................................................................................................................................. 106

9.3 Fuel Tank/Seat ........................................................................................................................................... 107

10. Removal and Installation of Motor .................................................................................................................... 109

10.1 Preparation Documents ............................................................................................................................ 109

10.2 Failure Diagnosis ..................................................................................................................................... 109

10.3 Disassembly of Motor .............................................................................................................................. 110

10.4 Installation ............................................................................................................................................... 111

Inspection and Maintenance of Engine .................................................................................................................... 112

11.Lubricaiting System ............................................................................................................................................ 114

11.1 Preparation Documents ............................................................................................................................ 114

11.2 Failure Diagnosis ..................................................................................................................................... 114

11.3 Fuel Pump ................................................................................................................................................ 115

12. Carburetor .......................................................................................................................................................... 118

12.1 Preparing Documents ............................................................................................................................... 118

12.2 Failure Diagnosis ..................................................................................................................................... 118

12.3 Carburetor Disassembly ........................................................................................................................... 119

12.4 Installation and Adjustment ..................................................................................................................... 121

13. Cylinder Cover .................................................................................................................................................. 123

13.1 Preparing Documents ............................................................................................................................... 123

13.2 Failure Diagnosis ..................................................................................................................................... 123

13.3 Cylinder Cover......................................................................................................................................... 123

13.4 Cylinder Cover Check ............................................................................................................................. 124

13.5 Installation of Cylinder Cover ................................................................................................................. 124

14. Cylinder Block and Piston ................................................................................................................................. 126

14.1 Preparing Documents ............................................................................................................................... 126

14.2 Failure Diagnosis ..................................................................................................................................... 127

14.3 Cylinder Block ......................................................................................................................................... 127

14.4 Piston ....................................................................................................................................................... 128

14.5 Piston Installation .................................................................................................................................... 130

15. Drive Face/Clutch/Driven Wheel/Kickstart Mechanism ................................................................................... 133

15.1 Preparing Documents ............................................................................................................................... 133

15.2 Failure Diagnosis ..................................................................................................................................... 133

15.3 Left Crankcase Cover .............................................................................................................................. 134

15.4 Drive Face ................................................................................................................................................ 134

15.5 Clutch/Driven Wheel ............................................................................................................................... 136

15.6 Breakdown of Clutch and Driven Wheel ................................................................................................. 137

15.7 Installation ............................................................................................................................................... 140

15.8 Kickstart Mechanism ............................................................................................................................... 141

16. Decelerator ......................................................................................................................................................... 143

16.1 Preparing Documents ............................................................................................................................... 143

16.2 Failure Diagnosis ..................................................................................................................................... 143

16.3 Gearbox ................................................................................................................................................... 143

16.4 Installation ............................................................................................................................................... 144

17. Crankcase........................................................................................................................................................... 146

17.1 Preparing Documents ............................................................................................................................... 146

17.2 Failure Diagnosis ..................................................................................................................................... 146

17.3 Crankcase ................................................................................................................................................. 147

17.4 Installation ............................................................................................................................................... 149

Inspection and Maintenance of Exhaust Emission System ...................................................................................... 150

18. Exhaust Emission & Control System................................................................................................................. 151

18.1 Warranty on the Exhaust Emission & Control System ............................................................................ 151

18.2 Instructions on Periodic Maintenance ...................................................................................................... 151

18.3 Mechanical Function of the Exhaust Control System .............................................................................. 152

18.4 Catalytic Conversion System ................................................................................................................... 152

18.5 Measures when the idle speed emission value exceeds the standard (Two-Stroke) ................................ 154

Preface

This maintenance manual is used for operating and maintaining Motorcycle

QJ50T-21U

Preparing Documents include all necessary instructions and statements. Please

carefully read this manual before operation.

Inspection & Adjustment states how to check and adjust your motorcycle. All

safety rules and maintenance regulations shall be carried out from the beginning of

periodic inspection.

Except for Chapter I, the rest chapters explain the disassembly/ assembly/

inspection of engine, entire motorcycle and electrical parts.

Breakdown drawing, systematic drawing, failure analysis and statements are

contained at the first part of each chapter.

Please note that photos, pictures or instructions are for your reference only. The

actual object may differ from this mentioned here. We will not make notification for

any discrepancy.

KEEWAY Motor Corporation Ltd.

Preparing Documents

General Safety Maintenance Rules

Specification Table Failure Diagnosis

General Safety

Carbon monoxide

Engine must be started up in a well-ventilated place, not in a closed area.

Note

Exhaust gas contains poisonous carbon monoxide, which may cause unconsciousness or even death of human.

Start up engine in an open place. The exhaust cleaning system shall be adopted if engine is started up in a closed

area.

Petrol

Ventilation is required for working places. Fire is strictly forbidden in any working place or where petroleum is

stored.

Battery

Battery emits explosive gas. Therefore, it shall be far away from fire sources, naked flame or smoking places.

Make sure good ventilation during charging.

Battery contains sulfuric acid (electrolyte). It will burn your skin or eyes when contacted. Therefore, wear

protective clothing and mask.

——Clean with fresh water immediately if electrolyte splashes on the skin.

——Clean with fresh water at least for 15 minutes immediately and then go to the doctor if electrolyte splashes

on eyes.

Electrolyte is poisonous. Drink a large quantity of fresh water, milk, milk of magnesia (laxative antacid) or mineral

oil if electrolyte is swollen accidently. Then go to the doctor. It shall be unreachable for children.

Do not remove the battery during commissioning. Otherwise, it may cause damage to inner parts of the vehicle.

Maintenance Rules

Metric tools are preferable for the maintenance of this motorcycle.

Improper tools may cause damage.

Clean up the surface of components or assembly parts before

removing or opening the shield for maintenance, which can

prevent dirt from falling into the engine, chassis or braking

system.

Wash and dry parts with air compressor after disassembly and before measurement of attrition value.

Solvent or oil can easily damage aging rubber articles. Check rubber before reassembly and replace rubber if

necessary.

套：boot

When loosening assembly parts, please start from outside to

inside. Small assembly parts shall be loosened first.

Complex assembly parts, such as gearbox, shall be stored in proper order for facilitating installation in the future.

Please specially note important connections before disassembly.

Replace parts which will not be in use before disassembly.

Bolts and screws with different length shall be separately used for

different assembly parts and shields, and they shall be correctly

mounted. Insert a bolt into a hole to check whether it is proper if

you are confused.

Fill the groove with grease before mounting an oil seal. Check

whether the oil seal is smooth or damaged during assembly.

When installing a hose (fuel, vacuum or cooling agent), insert its

end into the bottom of the connector so that the hose clip can

properly fix the connector. Rubber or plastic dirt-proof boot shall

be mounted at the original design position.

槽：groove 夹子：clip 接头：connector

During dismantling ball bearings, one or two (inside & outside)

bearing rollers shall be supported by tools. Ball bearings may be

damaged during disassembly and have to be replaced if only one

roller (either inside or outside) is imposed with force.

以上两例都会使轴承破裂：Bearings will be broken under either

occasion as mentioned.

Loose cables threaten electrical safety. Check each cable after

it is clamped to another for electrical safety;

Wire clamps are not allowed to bend towards welding point;

Bind cables at the designated place;

Do not deploy cables at the end of frame or at sharp point;

Do not deploy cables at the end of bolts or screws;

Cable deployment shall be far from heat source and where

cables may be clamped during moving;

Cables along the handlebar shall be neither too tight nor too

loose, and do not interface with any neighboring parts at

steering positions;

Cables shall be properly deployed without twist or knot;

Check whether the connector jacket is damaged and whether

the connector is over-stretched before mounting connectors;

Adopt adhesive tape or hosepipe to protect cables if they are

positioned at sharp point or corner;

Bind cables with tape after repairing;

Control cables shall not be bent or twisted. Clumsy operation

may be caused in light of damaged control cables.

Identification

1. The identification number of motorcycle is marked at the

frame ① : ;BBB941E?????????. The frame sign and the

anti-refitting sticker are fixed at the back of the frame. Take the

view from the back of the frame, the frame sign is fixed at the left ②and the on the right③. The frame sign is fixed with rivets

and the anti-refitting sticker is sticked with glue.

Fig. 1-1

2．The engine serial number① is printed on the shell of

crankcase. See fig. 1-2. The engine serial number is set like: KW1E40QMB-4*口口口口口口口口*.

Fig. 1-2

Significant Notes

1. Please apply valid Qianjiang parts and accessories. Any part or accessory not in accordance with the design

specification of Qianjiang Company may cause damage to engine.

2. Only metric tools are valid for maintenance and repair. Metric screws, bolts and nuts can not be exchanged with

imperial fasteners.

3. New gaskets, O-rings, cotter pins and locking pieces shall be applied for re-assembly.

4. Bolts with large diameter or positioned inside shall be fastened first and then diagonally screw down until

reaching required torque, otherwise there is special instruction.

5. Wash disassembled parts with cleanser. Lubricate all sliding surface before assembly.

6. Check whether all the parts and accessories are correctly mounted and operated after assembly.

7. Clean and remove oil before measurement. Add recommended lubricant to the lubricating areas during assembly.

8. Apply lubricant to the surface of engine and driving system if they are dismantled for long-term storage, which

can prevent rust and dirt.

Special Tools

Special tools refer to tools which are specially designed for assembling or disassembling some motorcycle

parts on special positions. Applicable special tools are necessary for precise adjustment and installation. With them,

parts and accessories can be mounted safely, reliably and rapidly, which improves efficiency and saves energy.

1．Tools for repairing the engine

Special tools are required for properly disassembling/assembling some engine parts.

Table and drawing (1-1, 1-2) of special tools for disassembling/assembling engine parts are as follows:

Table 1-1

Name

Remark

Special socket spanner

Clutch clamp holder

Flywheel puller

Feeler gauge

Bearing disassembly tools

Bearing assembly tools

Oil seal remover

Handle for dismantling tools

Piston pin pulling device

Piston pin pliers

Socket spanner for spark plug

Clutch thickness measuring device

Cylinder diameter measuring device

Dial indicator

Used for assembling/disassembling bolts for flywheels, Fig. 1-3

Fig. 1-4

Fig. 1-5

Fig. 1-6

Fig. 1-7

Fig. 1-8

Fig. 1-9

Fig. 1-10

Fig. 1-11

Fig. 1-12

Fig. 1-13

Fig. 1-14

Fig. 1-15

Measuring the inner diameter of piston pin, Fig. 1-16

Table 1-2 (continued)

Fig.1-3 Fig.1-4

Fig.1-5 Fig.1-6 厚度规（塞尺）：feeler gauge

Fig.1-7 Fig.1-8

Fig.1-9 Fig.1-10

①handle

Fig.1-11 Fig.1-12

①pliers ②piston

Fig.1-13 Fig.1-14

Fig.1-15 Fig.1-16

2．Tools for repairing the chassis

Table and drawing (1-17, 1-18) of ordinary tools and special tools for disassembling/assembling chassis parts are

as follows:

Table 1-17

Name

Remark

Torque spanner

Inner hexagon spanner

Socket spanner

Micrometer

Magnetic rack, V-block

Dial indicator

Vernier calipers

Circlip pliers

Screwdriver with striking cap

Tool for assembling oil seal of front fork

Tool for hammering seal of front fork

Steering nut spanner

Fig. 1-19

Fig. 1-20

Fig. 1-21

Fig. 1-22

Fig. 1-23

Fig. 1-24

Fig. 1-25

Fig. 1-26

Fig. 1-27

Fig. 1-28

Fig. 1-29

Fig. 1-30

(1) Ordinary tools for repairing the chassis

Table 1-18 (continued)

Fig.1-19 Fig.1-20

1. socket head 2. crank handle 3. ratchet spanner

Fig.1-21 Fig.1-22

Fig.1-23 Fig.1-24

Fig.1-25 Fig.1-26

Fig.1-27 Fig.1-28

（2）Special tools for repairing the chassis: tool for hammering seal of front fork

Fig.1-29

（3）Steering nut spanner

Fig.1-30

3．Tools for electric parts

Table and drawings (1-31, 1-32) of special tools for testing electric parts are as follows:

Table 1-31

Name

Remark

Multimeter

Ignition tester

Fig. 1-33

Fig. 1-34

Table 1-32 (continued)

Fig.1-33

Fig.1-34

Specification（QJ50T-21U）

Model

QJ50T-21U

Engine

Engine type

QJ1 E40 QMB -4

Length mm

1840

Fuel type

Unleaded petrol

（92/95）

Width mm

695

No. of

cylinder

Height mm

1140

ID × stroke

49.2×39.2

Wheelbase mm

1270

Total

displacement

50cc

Weight kg

(Curb weight)

Forward

shaft

Startup

Electric/kick

Backshaft

Cooling

Wind

Total

Lubrication

Divided

Tyre

Size

Front outer

tyre

120/70-12

Front rim

3.50×12

Air filter

e4 3XG

Rear outer

tyre

130/70-12

Rear rim

3.50×12

Capacity of

gasoline

tank

5.0L±0.2L

gear

Clutch

Dry centrifugal

clutch

Carburetor

type

IIF-45

Variable speed gear

Transmission

Stepless

Belt transmission

Performance

Idle speed

-rpm

1800±100rpm/min

Transmission

Belt transmission

Max. torque

4.55N.m/5200rpm

Electric devices

Battery

capacity/type

12V-3AH/

dry-charged

Max. Hp

2.63kW/5500rpm

Magnetor

capacity

89.6W/5000rpm

Compression

ratio

6.9：1

Spark plug

BR8HSA（NGK）

Max. speed

45km/h

Spark plug

gap

0.6-0.7mm

Braking

system

Dia. of front

brake disc

(mm)

φ190mm

Ignition

CDI

I.D. of rear

brake drum

(mm)

φ110mm

QJ50T-21U

N Y N Y Y N Y

Failure Diagnosis

Diagnosis on failure or difficulty in starting engine

Failure or difficulty in starting

Check ignition system

Remove the spark plug and check whether there is

carbon fouling between electrode.

Sparkover test for spark plug

Eliminate carbon fouling

Weak spark or no spark between electrode

Large blue or bluish purple spark between electrode

Screw off spark plug cap and conduct

sparkover test for high-voltage line

Check whether ignition is timely conducted

with an ignition timing lamp

Large blue spark

Weak spark or no spark

Check whether spark plug and cap are in

good condition

Check power

supply for ignition

Check whether short circuit or open circuit occurs to ignition coil

Check whether short circuit or open circuit occurs inside the ignition system

Check whether CDI ignition device is in good condition

Check the compression pressure of cylinder with pressure gauge

Check whether there is gasoline in the fuel tank

Normal

compression

pressure

Insufficient

compression

pressure

Add

gasoline

Non-contact ignition system for electromagnetic motor

1. Check whether short

circuit or open circuit occurs to ignition coil

2. Check whether short

circuit or open circuit occurs to trigger coil

1. Check whether CDI

ignition device is in good condition

2. Check whether

flywheels and trigger coil are loosened

Loosen drain screws of the carburetor and check whether there is gasoline in the overflow pipe

Dry electrode of spark plug

Check whether there is oil

spillover in the carburetor

1. Check whether the

float needle valve and the valve seat are firmly combined

2. Check whether the

conical surface of float needle valve is abrasive as stepped.

3. Check whether the

carburetor float is broken

4. Check whether the

carburetor float is too low

Check whether air filter is blocked

Flameout shortly after startup

Continue to work

after startup

The carburetor is blocked

inside or the float is too high

Startup device of

carburetor (startup &

enrichment system) is at fault

1. Check leakage on outer

connections of the engine.

2. Check whether the piston

ring is seized in the groove or whether it has enough elasticity.

3. Check abrasion of the piston

ring and the cylinder.

1. Check whether the

air vent in fuel tank cover is blocked.

2. Check whether the

fuel filter and the fuel switch are blocked.

3. Check whether the

fuel switch works normally.

4. Check whether the

oil hole of the carburetor is blocked.

5. Check whether the

carburetor float is too high.

Remove spark

plug and check

Y N Y N Y N N Y Y

Diagnosis on engine overheating

Engine overheating

Check whether operation is correct

1. Check whether gasoline grade is

improper or gasoline is stored for a long time

2. Check whether the engine works

at high speed for a long time or with overload during driving

Check cooling system

Air-cooled engine

Check whether heat sink is spotted or there is too much oil stain

Clean

Check whether cooling fan or air director is damaged (forcedly air-cooled engine)

Inspection & solution

Check whether ignition is timely conducted with an ignition timing lamp

1. Check whether

CDI ignition device is in good condition

2. Check whether

flywheels and trigger coil are loosened

Check whether clutch is slipping

Slipping clutch

Solution to slipping

clutch

Remove the spark plug; check the colors of spark plug insulators and judge the proportion of mixed combustible gas based on abnormity

The spark plug insulators are black; the exhaust muffler emits black smoke or causes backfire if the engine works at low speed; bad acceleration property; instable idle speed; flameout probability; it works normally at high speed.

The spark plug insulators are brown

The spark plug insulators are white; the engine may intermit during acceleration; the carburetor generates backfire; insufficient power of engine

Mixed combustible gas

is too dense.

1. Check whether the air filter is

blocked.

2. Check whether the startup device for

carburetor (startup & enrichment system) works normally.

3. Check whether the carburetor float is

too low.

Normal combustible gas mixture

Check whether the cylinder outlet or the exhaust muffler is blocked due to accumulated carbon fouling.

Check the lubrication system

Mixed combustible gas is diluted.

Lubrication system of the two-stroke engine

1. Check whether the

fuel switch works normally.

2. Check whether the

carburetor float is too high.

3. Check whether the

measuring jets and drill ways in the carburetor are blocked.

1. Check fuel level in the

crankcase.

2. Check whether fuel in the

crankcase has low viscosity or is dirty.

3. Check whether the fuel filter

is blocked.

4. Check whether the fuel pump

works normally.

5. Check whether the lubricant

channel is blocked.

Diagnosis on power shortage of engine

Power shortage of engine

Raise the main kickstand and suspend wheels; rotate

wheels with hands

Flexible rotating of wheels

Inflexible rotating of wheels

Check tyre pressure

1. Check whether there is

braking drag.

2. Check whether wheel

bearing is excessively abraded or damaged.

3. Check whether the middle

sleeve of hub is missed or too short.

Low pressure

Normal pressure

Check whether air leakage occurs to tyre valve and whether tyre is pierced or broken

Remove the spark plug and block the threaded hole with finger; press the startup button or step on the kick-start lever

Touch with your fingers and you can feel fierce air rushing out with puffing sound.

Touch with your fingers and you can not feel fierce air rushing out.

Normal compression pressure of cylinder

Insufficient compression pressure of cylinder

1. Check leakage on outer

connections of the engine.

2. Check whether the piston

ring is ruptured or seized in the groove or whether it has enough elasticity.

3. Check abrasion of the

piston ring and the cylinder.

Start the engine and slowly accelerate; observe the rotation speed change of engine.

The rotation speed of engine rises as it slowly accelerates.

The rotation speed of engine does not rise as it slowly accelerates.

1. 1. Check whether the clutch is slipping.

2. Check whether the driving belt is

excessively abraded.

3. Check whether the centrifugal roller of

driving pulley is excessively abraded.

4. Check whether the conical surface of

driving wheels and friction wheels is excessively abraded or abraded to be groove.

5. Check whether the conical surface of

driven wheels and moving driven wheels is excessively abraded or abraded to be groove.

6. Check whether the raceway on the inner

surface of friction wheels is excessively abraded or pressed to be concave.

1. 1. Check whether the fuel supply

system works normally.

2. Check whether the carburetor, air

filter and exhaust muffler are blocked.

3. Check whether the vacuum

diaphragm of plunger valve of carburetor is cracked or broken.

1. Check whether CDI

ignition device is in good condition

2. Check whether

flywheels and trigger coil are loosened

Check whether ignition is timely conducted with an ignition timing lamp.

Y N Y N N Y Y N Y

Diagnosis on abnormal idle speed of engine

Abnormal idle speed of engine

High idle speed

No idle speed

Unstable idle speed

Check compression pressure of cylinder

Check whether the carburetor throttle is completely closed with your hand.

Check whether ignition is timely conducted with an ignition timing lamp.

Insufficient compression

Normal compression pressure

1. Check leakage on

outer connections of the engine.

2. Check whether the

piston ring is ruptured or seized in the groove or whether it has enough elasticity.

3. Check abrasion of

the piston ring and the cylinder.

Adjust the idle speed of carburetor.

Check

whether idle jet is too big.

Check whether the steel wire rope of accelerator control cable is flexible when being pulled and whether the throttle valve spring is too soft.

1. Check whether

CDI ignition device is in good condition

2. Check whether

flywheels and trigger coil are loosened

Idle speed after adjustment

No idle speed after adjustment

The air adjusting screws of the carburetor or the adjusting screws of throttle valve are improperly

Check whether the carburetor idle jet, idle fuel way and air path are blocked.

Clean and clear

Check whether carburetor float is too high.

Adjust the float height to standard value.

1. Check whether the heat insulator of carburetor is

cracked.

2. Check whether the fixing nuts of carburetor are

loosened.

3. Check whether the negative pressure pipe of fuel

switch is broken.

4. Check whether air leakage occurs to reed valve.

Adjust the electrode gap.

Check the proportion of mixed combustible gas.

Check wheth er the electr ode gap of spark plug is too small.

Y N Y N Y

Diagnosis on excessive fuel consumption of engine

Excessive fuel

consumption of engine

Check whether operation is correct

Raise the main kickstand and rotate wheels with hands

1. Check whether the motorcycle

runs with overload or not at economical speed or at low gear.

2. Check whether petrol grade is

proper.

Inflexible rotating of wheels

Flexible rotating of wheels

1. Check whether

there is braking drag.

2. Check whether

wheel bearing is seriously abraded or damaged.

3. Check whether

the middle sleeve of hub is missed or too short.

Check tyre pressure

Low pressure

Normal pressure

Inflate as required

Check whether oil leakage occurs in fuel tank, fuel switch, fuel pipe or carburetor.

Solve problems based on actual situation

Check the proportion of mixed combustible gas.

Normal combustible gas mixture

Mixed combustible

gas is too dense.

Mixed combustible gas is diluted.

Check whether the idle speed of engine is too high.

1. Check whether the air

filter is blocked.

2. Check whether the

carburetor float is too low.

3. Check whether the main

measuring jet of carburetor is too big.

1. Check whether the

carburetor is blocked inside.

2. Check whether the

carburetor float is too high.

Check and adjust the carburetor.

Check whether ignition is timely conducted with an ignition timing lamp

Check whether the driving belt of clutch is slipping.

Check the ignition system.

Diagnosis on dense bluish white smoke from the exhaust muffler of the two-stroke engine

Diagnosis on difficulty in transmission shift

The exhaust muffler of the two-stroke engine emits dense bluish white smoke.

Check whether the fuel level in the crankcase exceeds the upper limit.

Excessive fuel filling into the crankcase. Drain out the excessive part and make sure the fuel level is not over the upper limit.

1. Check whether the cylinder, the piston and the

piston ring are excessively abraded.

2. Check whether the piston ring has enough

elasticity or whether it is seized in the groove.

3. Check whether piston ring joint is staggered.

Difficulty in Transmission Shift

Start the engine and check whether the idle speed is too high.

Re-adjustment

Check whether it is coordinated when shifting

Check whether the clutch is completely released Improve operation

Check whether the gearshift shaft is deformed or the gearshift arm is deformed or excessively abrasive

1. Check whether the free stroke of the

clutch grip is between 10mm~20mm.

2. Check the balanced elasticity of clutch

spring.

3. Check whether the tooth-shaped groove

of the drive hub and the driven hub is abraded to be jagged.

4. Check whether the driven disc of the

clutch is bent or deformed.

5. Check whether components of the clutch

lever are excessively abrasive.

Replace

1. Check whether the groove of the gearshift

cam is excessively abrasive or damaged.

2. Check whether the fork hole is

excessively abrasive.

3. Check whether the fork is deformed.

4. Check whether the fork shaft is deformed

or excessively abrasive.

Start up the engine and remove the dipstick when it works at high speed. Check whether there is smoke from the fuel filler.

N Y N Y N

Y N N

Diagnosis on transmission gear skip shift

Diagnosis on clutch slipping

Clutch slipping

Automatic shoe-type centrifugal & dry clutch is slipping.

Check whether the shoe-type friction plate is excessively abraded.

Replace the whole set of clutch shoes

Clean and remove oil stain

Check whether the contact surface area between shoe-type friction plate and friction disc is beyond 70%.

Check whether the contact surface between shoe-type friction plate and friction disc is excessively abraded.

Repair or replace clutch shoes

Check whether the shoe-type friction plate is spotted with oil stain.

Transmission gear

skip shift

Check whether the positioning wheel spring is ruptured or lacks elasticity.

Replacement

Disassemble crankcase and check whether the engagement depth for each gear is in accordance with requirements.

Proper depth in engaging

Insufficient depth in engaging

Check whether the engaging end of the cam claw on the engaged gear face is abraded to be conical or largely circular, and whether the groove on the corresponding gear face is abraded to be trumpet-shaped.

Check whether the shift fork is excessively abraded or deformed.

Replace gear

Check whether the spline teeth of main shaft/countershaft and the spline groove in the clash gear are

Replace shift fork

1. Check whether shift fork hole and shift

shaft are abraded.

2. Check whether the gap between shift fork

pin/gearshift shaft and cam groove is too big.

3. Check whether the installation of

N Y Y N N

Diagnosis on malfunction of hydraulic disc brake

Diagnosis on malfunction of drum brake

Malfunction of hydraulic disc brake

Check the level of brake fluid inside the brake fluid reservoir.

The level of brake fluid is below the lower limit of the reservoir.

The level of brake fluid is beyond the lower limit of the reservoir.

Add brake fluid until it is beyond the lower limit; check whether there is oil leakage in brake caliper, brake hose and hose joints.

Do you have "sponge" feeling when operating brake lever?

There is air left in the oil passage of brake system.

Check whether the abrasion of brake friction plate reaches limit mark and whether the brake disc is excessively abraded.

Replace brake friction plate and brake disc.

Malfunction of drum

brake

Check whether the free stroke of brake lever is within 10mm ~ 20mm or whether the free stroke of brake pedal is within 20mm ~ 30mm.

Readjustment

Separate the brake arm and the steel wire rope of brake control cable; check the brake arm with hands.

The brake arm works flexibly but you can feel resistance when griping the lever.

The brake arm works inflexibly.

The indication arrow on the brake cam points to or beyond the sign “▽” on the brake hub cover.

The indication arrow on the brake cam does not align with the sign “▽” on the brake hub cover.

The steel wire rope of brake control cable is inflexible when pulling.

1. Check whether the curved surface of

brake cam is excessively abraded.

2. Check whether the friction plate of brake shoe is excessively abraded.

3. Check whether the inner diameter of brake hub is excessively abraded.

1. Check whether the piston surface of master brake pump and the wall of oil tank

are excessively abraded or damaged.

2. Check whether the piston cup of master brake pump is damaged, cracked or aged.

3. Check whether the seal of brake caliper is damaged, cracked or aged.

4. Check whether the piston surface of brake caliper and the wall of oil tank are

excessively abraded or damaged.

The moving part of brake cam is rusty or blocked by something.

1. Check whether the friction surface

of brake shoe is spotted with oil stain.

2. Check whether the contact surface area of the friction plate of brake shoe and the brake hub is less than 70%.

Diagnosis on battery charging failure

Battery charging

failure

Resistance value lower than standard value

Short circuit of charging coil

Infinite resistance

value

Resistance value in accordance with standard value

Open circuit of charging coil or output conductor.

Set the multimeter to DC voltage 0V~20V; measure the voltage between the conductor terminal (connector to battery) (normally red wire or red/white wire) and the negative pole.

Bad connection or open circuit between the electromagnetic motor and the rectifier or the rectifier regulator

No voltage

Voltage available

Open circuit between the connector and the battery.

Check whether the rectifier or the rectifier regulator is broken down with an ohm meter.

Remove the connector between the conductor bundle of electromagnetic motor and the cable assembly; measure the resistance between the output conductor terminals of charging coil and check whether it is in accordance with the standard.

Connect power to the connector between the conductor bundle of electromagnetic motor and the cable assembly; cut off the connector between the

Measure the resistance between the output conductor terminals of charging coil of the connector and check whether it is in accordance with the standard.

Y N Y

Diagnosis on insufficient battery charging

Insufficient battery

Check whether the brake lamp is always light.

Adjust or replace the brake lamp switch.

Leakage current smaller than the required.

Leakage current larger than the required (normally it shall be no more than 1mA).

Check whether the charging coil of the magnetor is short-circuit.

Short circuit between the rectifier or the rectifier regulator or the battery and the ignition switch

Replace the charging coil

1. Check whether the battery electrolyte is

enough.

2. Check whether the battery electrolyte is

diluted.

3. Check whether the battery electrode plates

are vulcanized or short-circuit.

Set the ignition switch to “OFF”; remove the negative cable from the battery; connect the negative electrode of the ammeter to the battery negative terminal and the positive electrode to the positive terminal; check current leakage.

Riding-style motorcycle

Motorcycle scooter

Y N Y

Diagnosis on starter motor failure in rotation

The electric horn does not make sound or makes weak sound; the steering lamp emits weak light.

The electric horn makes loud sound and the steering lamp emits bright light.

Battery power shortage or bad contact of conductor joint

Grip the brake lever (motor scooter), or make the transmission at neutral gear, or grip the clutch lever; press the startup button.

Starter motor failure in

rotation

Turn the ignition switch; press the horn or turn the

steering lamp switch.

Press the startup button and there is no joint sound from starter relay.

Press the startup button and there is joint sound from starter relay.

Disassemble the connector of starter relay from the cable assembly; use two lead wires to connect the battery with two down-leads of the starter relay coil.

Use screwdriver or large-diameter lead wire to short-circuit the battery terminal on the starter relay and the starter motor terminal.

The starter relay works normally after connection

The starter motor works normally after short circuit.

The starter motor does not work after connection, and there is no sound from starter relay.

The starter motor does not work after short circuit.

Open circuit or short circuit of starter relay coil.

Check the inner circuit of the electric starting control system

Contacts of starter relay are burnt or damaged.

Disassemble the starter motor and check:

1. whether the carbon brush is

excessively abraded;

2. whether the carbon brush spring

is ruptured or lacks elasticity;

3. whether the armature

commutator is excessively abraded;

4. whether open circuit or short

circuit occurs to the armature coil.

1. Check whether the

contact of starting button is in good condition.

2. Check whether the

commutation diode is damaged.

3. Check whether the

neutral gear switch works normally.

4. Check whether open

circuit or short circuit occurs to the inner circuit of electric starting control system.

Check whether the contact of starting button is bad.

Grip the brake lever and check whether the brake lamp is light.

Bad contact inside the brake lamp switch or open circuit of its auxiliary circuit.

Repair or replace starting button

Open circuit or short circuit inside the electric starting control system

+ 126 hidden pages

KEEWAY QJ50T-21U Maintenance Manual

Specifications and Main Features

Frequently Asked Questions

User Manual