Baotian BT49QT-21B1 User manual

BT49QT-21B1 MODEL
SERVICE MANUAL

BT49QT-21B1 MODEL SPARE PARTS NAME：
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CONTENTS
SUMMARY 1
CHAPTER ONE MAINTENANCE OF THE MOTORCYCLE
Ⅰ. ITEMS OF MAINTENANCE 2
Ⅱ. PERIODIC MAINTENANCE SCHEDULE AND MAINTENANCE LOCATIONS 2
Ⅲ. MAINTENANCE SPECIFICATIONS 5
Ⅳ. THROTTLE ACTUATION INSPECTION 6
Ⅴ. AIR FILTER INSPECTION AND CLEANING 7
Ⅵ. BR A K E B L O C K S I N S P E CT I O N 7
Ⅶ. BRAKE SYSTEM INSPECTION, ADJUSTMENT AND REPLACEMENT 8
Ⅷ. FRONT AND REAR SHOCK ABSORBER INSPECTION 9
Ⅸ. FRONT WHEEL AND REAR WHEEL INSPECTION 10
Ⅹ. STEERING STEM INSPECTION 11
CHAPTER TWO MAINTENANCE INFORMATION
Ⅰ. FRAME NUMBER AND ENGINE NUMBER LOCATION 12
Ⅱ. PRECAUTIONS IN OPERATION 12
Ⅲ. SPECIFIED TORQUES 13
CHAPTER THREE BODY TROUBLESHOOTING
SECTION ONE BODY COMMON TROUBLES AND TROUBLE DETECTION 15
SECTION TWO DETAILED DESCRIPTIONS OF BODY PARTS TROUBLES
Ⅰ. FRONT WHEEL SERVICE 18
Ⅱ. FRONT BRAKE SERVICE ( DISK BRAKE ) 20
Ⅲ. FRONT SHOCK ABSORBER SERVICE 23
Ⅳ. FRONT FORK SERVICE 23
Ⅴ. HANDLEBAR SERVICE 25
Ⅵ. REAR WHEEL SERVICE 26
Ⅶ. REAR BRAKE SERVICE 27
Ⅷ. REAR SHOCK ABSORBER SERVICE 28

1
SUMMARY
This 2-stroke scooter BT49QT-21B1 is with low weight, enough power, low oil
consumption and good operating performance.
This manual is for maintenance men to repair and maintain BT49QT-21B1 and it is
also useful when maintain other models.
This manual holds the latest technical information. We reserve the right to amend the
data, instructions and specifications without advice.
The technical specifications of BT49QT-21B1:
Size and weight:
Length × width × height 1940×720×1150 Unloading weight 100kg
Wheel space 1300 Max. mass 254 kg
Front tire pressure 225KPa Fuel tank capacity 4.5±0.5L
Rear tire pressure 225KPa Max. speed 45Km/h
Engine:
Type 139QMA-A Lubricate method Pressure spray
Stroke 4 Lubricant brand SAE15W/40SF
Cylinder diameter × driving
distance
39mm × 41.4mm Gasoline brand 90# or above
Cylinder capacity 49cm
3
Clutch type Automatic acentric
Compression ratio 10.7±0.1:1 Transmission type Nonpolar
Max torque:
N.m/(r/min) 3.88/6500 Starting method Electric/kick starting
Max power output:
kw/(r/min) 3.15/8500 Ignition method CDI
Idling speed: r/min 1900±100 Cooling system Forced air-cooled
Electric system:
Battery 12V 6AH Turning signal light 10W,12V
Headlight 35/35W,12V Position light 5W,12V
Taillight/brake light 5/21W,12V Fuse specification 10A

2
CHAPTER ONE MAINTENANCE OF THE MOTORCYCLE
Ⅰ
ⅠⅠ
Ⅰ. ITEMS OFMAINTENANCE
When the motorcycle is used, parts loose and mechanical wear inevitably occur to
varied extents. Neglecting of timely maintenance not only reduces its mechanical
function, economic performance, stability and durability, but also threatens the safety
of the motorcycle and the rider. Correct and timely maintenance of the motorcycle is
necessary. Items of maintenance refer to the parts and positions for maintenance.
Different items of maintenance are affected in different intervals and in different
manners.
1. Running-in Maintenance
This is the maintenance at the end of the first 1000km and is an all-round inspection
of motorcycle. A newly-bought motorcycle or a motorcycle fresh from an overhaul
might be severely overheated as a result of severe friction between the moving parts
which might be imperfect in finishing or fitting. Neglecting in use might lead to
damage of the friction surfaces and might threaten the performance, and the service
life of the motorcycle. Please observe the following points:
Restrict the speed in speed range specified in the instruction manual.
Restrict the load to 2/3 of the maximum load and ride in fairly good road
conditions.
Restrict the length of riding time to avoid long-time running of the engine.
Replace engine oil at short intervals so that metal chips caused in the running-
in period can be discharged. It is recommended to replace engine oil for 3 times
during the running-in period.
2. Routine Maintenance
Routine maintenance is the basis of all kinds of maintenances. It refers to the daily
maintenance, including cleaning, inspecting and common troubleshooting.
3. Periodic Maintenance
This maintenance is to restore normal performance of the motorcycle. The
maintenance is classified into first-grade periodic technical maintenance and second-
grade periodic technical maintenance (also known as items of maintenance) according
to different mileages. Generally speaking, a first-grade maintenance is effected after
the initial 4000km and a second-grade maintenance is effected every 8000km. As the
service time extends, maintenance intervals should be shortened accordingly.
Ⅱ
ⅡⅡ
Ⅱ. PERIODIC MAINTENANCE SCHEDULE AND MAINTENANCE LOCATIONS
After a period of using (one day, one month or half a year, for example) or a certain
mileage (1000km, 4000km, 8000km, for example), an all-round maintenance
operation should be effected, including comprehensive inspection, adjustment,
tightening, lubrication, cleaning or replacement. The specific regulation made
according to time intervals or mileages is known as maintenance interval. The
motorcycle maintenance schedule is as follows.

3
1. Maintenance Schedule Maintenance Schedule
time
item Mileage 1000km
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000
Engine oil New R
300km R R R R R R R R R R R
Engine oil
strainer C C
Gasoline
strainer R
Gear oil Note 4 New R
300km R R
Throttle play A A A A
Carburetor I I C
Air filter Note 3,
4 I R R
Spark plug Clean every 3000km, replace when necessary
Brake system I I I I I I I I I I I I
Drive belt I
Suspension I I I
Tire I I I
Steering rod
bearing I I I
Screws and
bolts of parts I I
Rear brake
cam C
Notes:
1. I: Inspect and when necessary, clean, lubricate, supplement, modify or replace.
A: adjust; C: clean; R: replace; T: tighten.
2. Effect periodic maintenance according to the instructions in the user’s manual.
3. When the mileage exceeds the range specified in the schedule, repeat the
maintenance.
4. In dusty or rainy conditions, inspection and replacement should be effected
earlier.
5. In heavy load, long distance or rainy conditions, replacement should be
effected earlier.

4
2. Maintenance locations

5
Ⅲ
ⅢⅢ
Ⅲ. MAINTENANCE SPECIFICATIONS
The basic methods of motorcycle maintenance include inspection, adjustment,
tightening, lubrication, cleaning, supplementing and replacement, which constitute the
main elements of maintenance.
1. Inspection
Inspection refers to basic inspecting operations in accordance with items and
requirements specified in the user’s manual, including inspection with
instruments or with eyes for abnormalities in machine parts, directly
comparing related data and aligning with tools and gauges.
2. Adjustment
Adjustment refers to inspection-based adjustment and rectification of some
specified machine parts, including adjustment of machine part plays and
rectification of misfittings and deformations so as to restore correct positions,
forms and plays.
3. Tightening
Tightening refers tightening of bolts, screws and nuts of machine parts with
tools so as to avoid loosening of machine parts and to obtain specified
tightening torques.
4. Cleaning
Cleaning is needed where call for cleanliness and tidiness. Cleaning
operations include all the means and measures taken to remove dust,
contamination, metal chips, oily stains and carbon deposits that might lead to
pipe clogging or reduction in motorcycle performance. Cleaning measures are
washing, carbon deposit removing, rubbing, cleaning and clearing.
5. Lubrication
In order to facilitate smooth and easy running of moving machine parts,
including swinging parts, reciprocating parts, sliding parts and vibrating parts,
to reduce scuffing, abrasion, deformation and to reduce friction, it is
necessary to coat or spray these parts with a lubricant. Different lubricants
and lubricating methods are required for different machine parts with
different functions. Application of lubricants to machine parts is known as
lubrication.
6. Replenishing, supplement and replacement
These operations refer to addition of oil, lubricants, cooling water, electrolyte,
fuel and replacement of damaged parts with new ones and replacement of
denatured oils with new oils.

6
IV. THROTTLE ACTUATION INSPECTION
Inspect throttle grip for easy and smooth
movement.
Inspect throttle free travel.
Free travel: 2-6mm
The main adjusting position is beside the
carburetor.
Remove rear luggage box cover.
Adjust by loosening the fastening nut and
turning the adjusting nut.
Fine adjustment is effected on the side of
the throttle grip.
Effected adjustment is by removing the
dust cover, loosening the tightening nut and
turning the adjusting nut.

7
Ⅴ
ⅤⅤ
Ⅴ. AIR FILTER INSPECTION AND CLEANING
After a certain mileage, dust and impurities will gather in air filter case and strainer,
which will clog strainer pores and reduce inlet of air and thus lead to excessive
concentration of mixed gas and reduce the performance of engine. That’s why the
strainer must be cleaned every 2000-3000km and in dusty or rainy conditions strainer
must be cleaned or replaced earlier.
Remove 5 tightening screws of air filter.
Remove strainer cover.
Take out the foam strainer.
Immerse foam strainer in gasoline and
wash it to remove dust and impurities by
gripping and pressing.
Press gasoline out of the foam.
Soak the cleaned foam with engine oil,
press out or throw out engine oil to leave it
moist with oil.
Mount.
VI. BRAKE BLOCKS INSPECTION
Grip the brake lever and check the wear
& tear indicator on the brake blocks. If the
indicator nearly touched brake disc, the
brake blocks must be replaced with new
ones.
cleaning gripping gasoline soaking gripping
¢ Û
¢ Ú
¢ Ù
¢ Ù--- wear & tear indicator
¢ Ú--- brake disc
¢ Û--- brake blocks

8
VII. BRAKE SYSTEM INSPECTION, ADJUSTMENTAND REPLACEMENT
1. Front brake (disk brake)
Remove the bolts linking brake caliper
and front shock absorber.
Remove brake caliper.
* Do not pull brake lever when brake
caliper is removed so as to prevent jamming
of brake block.
If brake block is jammed, pry it with
screwdriver and push piston back into
caliper.
Brake Block Replacement:
Brake block must be replaced when it is
worn to the limit of use.
* It is not necessary to remove brake oil
pipe when replacing brake block.
* Brake block must be replaced as a set.
Remove the brake block pins.
Take out the old brake blocks and mount
a set of new brake blocks.
Effect mounting in an order reversed to
that of dismounting.
Brake Disc Inspection:
Inspect brake disc thickness.
Limit of use: 3.0mm
Inspect brake disc angularity.
Limit of use: 0.3mm

9
2. Rear Brake
Inspect rear brake lever free travel.
Free travel: 10-20mm
Turn adjusting nut to effect adjustment
when free travel exceeds limit.
VIII. FRONT AND REAR SHOCK ABSORBER INSPECTION
1. Front Shock Absorber
Tighten front brake lever, press front
shock absorber up and down and inspect
actuation.
Inspect front shock absorber to see if
there is leakage of oil and if there is damage
or loosening.
2. Rear Shock Absorber
Press rear shock absorber to inspect
actuation. Inspect rear shock absorber to see
if there is oil leakage and if there is damage
or loosening in machine parts.
Lift rear wheel, press rear wheel right and
left to inspect if engine suspension lug
buffer bush is loose.

10
IX. FRONT WHEELAND REAR WHEEL INSPECTION
Wheel Rim Inspection:
Inspect wheel rim, remove rust stains and rubber chips.
Deformation and fissures are causes of air leakage. Do not use wheel rims in the
following cases:
Bruise of wheel rim face contacting tire bead ring exceeds 0.5mm in depth and
1.0mm in width.
Tire Inspection:
Inspect if there is fissure or iron nail in the tire.
In one of the following conditions, tires must be replaced instead of repair.
Puncture of tire by a foreigner matter 6mm in diameter or tire fissure.
Layered tire.
Chunking of tread
Damaged tire bead
Broken tire bead or other tire bead damages
Broken tire cord
Damage due to forced dismounting
Fissure extending to frame
Abnormal inner lining
Tire groove wear: front wheel <0.8mm, rear wheel < 0.8mm.
Punctured or otherwise damaged tire flank
Inspect tire pressure by means of a tire pressure gauge
* Tire pressure should be inspected when the motorcycle is in a cold state.
Specified pressure Unit: kPa
Front wheel 225
Rear wheel 225
Tire Specifications:
Front wheel 110/70-12
Rear wheel 110/70-12

11
Inspect if front wheel nut is loose.
Inspect if rear wheel nut is loose.
If loose, tighten them to specified torques.
Torques: front wheel nut 60N·m
rear wheel nut 120N·m
X. STEERING STEM INSPECTION
Swing handlebar right and left to see if
there is interference such as wire or other
things.
Turn front wheel to see that handlebar is
easy in operation.
In case of any difficulty in operation,
inspect steering stem bearing assembly.

12
CHAPTER TWO MAINTENANCE INFORMATION
I. FRAME NUMBER AND ENGINE NUMBER LOCATION
II. PRECAUTIONS IN OPERATION
Removed washers, 0-rings, elastic retaining rings and split pins must be
replaced with new ones.
When mounting bolts, nuts and screws, proceed from trial tightening, from
larger diameters to smaller diameters and inner ones to outer ones in a
diagonally order. Tighten them to specific torques.
Parts and greases must be those made by our factory or recommended by our
factory.
Special operations must be effected with special tools or specified universal
tools.
Removed parts must be rubbed or cleaned before they are inspected or
measured. They must be coated on the sliding faces before mounting.
They must be greased at the specified positions with designated or equivalent
greases.
Parts must be tightened and their performances inspected at their positions
when mounted.
The battery’s negative terminal must be disconnected before operation.
Make sure that tools such as wrenches are not in contact with the frame.
At the completion of operations, reconfirm correct connections and fastenings.
The positive terminal must be connected first in case of a removed battery.
Connected terminals must be coated with lubricant.
The terminals must be completely covered with caps.
When a fuse is burnt, inspect the cause and replace the fuse with a fuse of
equivalent capacity.
At the completion of operation, completely cover terminals with caps.
When removing connectors with locks, they must be unlocked before operation.
When removing connectors, the connectors proper must be held instead of
pulling their wires.
Before connecting connectors, confirm that they are free from breakage,
bending, over length or loosening.

13
Connectors must be inserted home.
When connecting connectors with locks, confirm that their locks are fastened.
Confirm that the wires are not loose.
Confirm that connectors’ plastic sleeves completely cover the connectors
without fail.
Before connecting the connectors, confirm that their sleeves are free from
breakage and their terminals are not oversized.
Connector plugs must be fully inserted.
Confirm that plastic sleeves completely cover the terminals.
Plastic sleeves should not be placed with the open side up.
Wire bunch bands should be fixed at the specified position of motorcycle frame.
Wire clamps must correctly keep wires in place.
Avoid welding stains of welded clamps when clamping wires.
Wire bunches must be fixed away from turning or moving parts.
Do not damage the covering of wire bunches.
In case of wire bunch defects, remedy it with insulating bands.
Wire bunches must not be covered with mounted parts.
Do not twist or bend cables by force. Deformed or damaged cables would
result in poor rotation or damage.
Ⅲ
ⅢⅢ
Ⅲ. SPECIFIED TORQUES
Torques at important positions and standard torques of other positions are as
follows:
SPECIFIED TORQUES
Frame:
Designations of tightening positions Number
Thread
specification
Torques:
N·m
Engine suspension lug mounting nut 1 M10 45
Engine mounting nut 1 M10 45
Front axle nut 1 M12 60
Rear axle nut 1 M16 120
Rear shock absorber upper mounting bolt 1 M10 40
Rear shock absorber lower mounting bolt 1 M8 25
Front shock absorber upper lock bolt 2 M10 40
Steering stem lock nut 1 M25 70
Handlebar mounting nut 1 M10 45
Upper bearing top 1 M25 2.5
Exhaust muffler connector nut 2 M6 12
Exhaust muffler mounting bolt 2 M8 35

14
Standard Torques:
Designations Torques: N·m
Bolt, nut M5 5
Bolt, nut M6 10
Bolt, nutM8 21.5
Bolt, nut M10 35
Bolt, nut M12 55
Screw M5 4
Screw M6 9
Flange bolt, nut M6 12
Flange bolt, nut M8 27
Flange bolt, nut M10 40

15
CHAPTER THREE BODY TROUBLESHOOTING
SECTION ONE BODY COMMON TROUBLES AND TROUBLE DETECTION
Body part common troubles and possible causes are as follows:
Troubles Causes Details (reference)
Over tightening of handlebar
adjusting nut
Handlebar rotation
not easy (strenuous
turning or unstable
tightness) Steering stem over worn Refer to “Front Fork
Service”
Incorrect mounting of brake cable or
tachometer cable Refer to “Handlebar
Service”, “Front
Fork Service”
Remarkable deformation of steering
stem due to outside impact
Over tightening of steering stem top
ball bearing retainer
Damaged or broken ball bearing
Refer to “Front Fork
Service”
Heavy steering stem
turning
Reduced tire air
Refer to “Front
Wheel Service”,
“Rear Wheel
Service”
Imbalance of right and left shock
absorbers
Refer to “Front
Shock Absorber
Service”
Bent front fork Refer to “Front Fork
Service”
Deflected steering
stem
Bent front tire, deflected tire Refer to “Front
Wheel Service”
Normal wear of brake lining
Hardened brake block or dusty block
Excessive front brake and rear brake
Damaged brake cable
Brake cam rotation not easy
Worn brake block
Drum brake failure
Worn or slotted brake drum bore
Refer to “Brake
System Inspection,
Adjustment and
Replacement”, “Rear
Brake Service”
Bent brake lever
Air in hydraulic
device
Leakage in hydraulic
device
Disk brake failure Feeble brake
lever
Clogged hydraulic
passage
Refer to “Brake
System Inspection,
Adjustment and
Replacement”,
“Front Brake
Service”

16
Chart continued
Troubles Causes Details (reference)
Inadequate liquid
Contaminated brake
block and brake disc
Bent or deformed
brake disc
Contaminated brake
caliper
Worn seal ring of
brake caliper piston
Viscous or worn
brake caliper piston
Inability of brake
caliper normal
sliding
Worn main cylinder
piston seal ring
Viscous or worn
main cylinder piston
Feeble brake
lever
Contaminated main
cylinder
Clogged narrow
brake system
Clogged narrow
liquid passage
Viscous worn brake
caliper
Inability of brake
caliper normal
sliding
Worn seal ring of
brake caliper piston
Stiff brake
lever
Viscous or worn
main cylinder piston
Contaminated brake
block and brake disc
Bent or deformed
brake disc
Inability of brake
caliper normal
sliding
Disk brake failure
Resisted
braking
Wheel not adjusted
straight
Refer to “Brake
System Inspection,
Adjustment and
Replacement”,
“Front Brake
Service”

17
Chart continued
Troubles Causes Details (reference)
Hardened brake block surface or
dusty block
Uneven or slotted brake block
surface
Serious wear of brake block lining
Abnormal braking
sound
Serious slots inside brake drum
Refer to “Rear Brake
Service”
Steering stem rotation not easy Refer to “Front Fork
Service”
Bent shock absorber
Shock absorber oil leakage Refer to “Front Shock
Absorber Service”
Bent front axle, incorrect wheel
mounting
Roundness error of wheel rim
Deformation of wheel rim
Deviation of
motorcycle direction
(inclining to roadside)
Inadequate tire pressure
Refer to “Front Wheel
Service”
Deformed wheel rim
Loose front wheel bearing
Poor tire
Front wheel oscillation
Poor axle locking
Refer to “Front Wheel
Service”
Soft front shock
absorber Spring fatigue Refer to “Front Shock
Absorber Service”
Deformed wheel rim
Rear wheel oscillation Poor wheel Refer to “Rear Wheel
Service”
Soft rear shock
absorber Spring fatigue Refer to “Rear Shock
Absorber Service”