2004 YAMAHA YZ125LC Fork

CHAPTER 4
ENGINE
SEAT, FUEL TANK AND SIDE
COVERS.....................................................4-1
EXHAUST PIPE AND SILENCER..............4-3
RADIATOR..................................................4-4
CARBURETOR AND REED VALVE...........4-7
CYLINDER HEAD , CYLINDER AND
PISTON.....................................................4-17
CLUTCH AND PRIMARY DRIVEN
GEAR.......................................................4-30
KICK AXLE, SHIFT SHAFT AND
PRIMARY DRIVE GEAR...........................4-38
YPVS GOVERNOR...................................4-46
WATER PUMP..........................................4-49
CDI MAGNETO.........................................4-53
ENGINE REMOVAL..................................4-57
CRANKCASE AND CRANKSHAFT.........4-62
TRANSMISSION, SHIFT CAM AND
SHIFT FORK.............................................4-69
CHAPTER 5
CHASSIS
FRONT WHEEL AND REAR WHEEL........5-1
FRONT BRAKE AND REAR BRAKE.......5-10
FRONT FORK...........................................5-26
HANDLEBAR............................................5-39
STEERING................................................5-46
SWINGARM..............................................5-51
REAR SHOCK ABSORBER.....................5-59
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1-1
GEN
INFO
DESCRIPTION
EC100000
GENERAL INFORMATION
EC110000
DESCRIPTION
1Clutch lever
2“ENGINE STOP” button
3Front brake lever
4Throttle grip
5Radiator cap
6Fuel tank cap
7Kick starter
8Fuel tank
9Radiator
0Coolant drain bolt
qCheck bolt (Transmission oil level)
wRear brake pedal
eValve joint
rFuel cock
tAir cleaner
yDrive chain
uShift pedal
iStarter knob
oFront fork
NOTE:
9The machine you have purchased may differ
slightly from those shown in the following.
9Designs and specifications are subject to
change without notice.
5XE-9-30-1A 4/16/03 10:22 AM Page 2

1-8
GEN
INFO
SPECIAL TOOLS
Part number Tool name / How to use IIIustration
YU-24460-01, 90890-01325Radiator cap testerYU-24460-01 90890-01325
YU-33984, 90890-01352 AdapterYU-33984 90890-01352
These tools are used for checking the cooling
system.
YU-33975, 90890-01403 Ring nut wrench
YU-33975 90890-01403
This tool is used when tighten the steering ring nut
to specification.
YM-01442, 90890-01442 Fork seal driver
YM-01442 90890-01442
This tool is used when install the fork oil seal.
YM-01494, 90890-01494 Damper rod holder
YM-01494 90890-01494
Use this tool to remove and install the damper rod.
YU-3112-C, 90890-03112 Yamaha pocket tester
YU-3112-C 90890-03112
Use this tool to inspect the coil resistance,
output voltage and amperage.
YM-91042, 90890-04086 Clutch holding tool
YM-91042 90890-04086
This tool is used to hold the clutch when removing
or installing the clutch boss securing nut.
YM-34487 Dynamic spark tester
YM-34487 90890-06754
90890-06754 Ignition checker
This instrument is necessary for checking the igni-
tion system components.
ACC-QUICK-GS-KT Quick gasket
®ACC-QUICK-GS-KT 90890-85505
90890-85505 YAMAHA Bond No. 1215
This sealant (Bond) is used for crankcase mating
surface, etc.
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1-16
GEN
INFO
TORQUE-CHECK POINTS
EC1A0013
TORQUE-CHECK POINTS
Frame construction Frame to rear frame
Combined seat and tank Fuel tank to frame
Engine mounting Frame to engine
Engine bracket to engine
Engine bracket to frame
Steering Steering shaft to Steering shaft to frame
handlebar Steering shaft to handle crown
Handle crown to handlebar
Suspension Front Steering shaft to Front fork to handle crown
front fork Front fork to under bracket
Rear For link type Assembly of links
Link to frame
Link to shock absorber
Link to swingarm
Rear Installation of shock Shock absorber to frame
absorber
Rear Installation of swingarm Tightening of pivot shaft
Wheel Installation of wheel Front Tightening of front axle
Tightening of axle holder
Rear Tightening of rear axle
Wheel to sprocket
Brake Front Caliper to front fork
Brake disc to wheel
Tightening of union bolt
Master cylinder to handlebar
Tightening of air bleeder
Rear Brake pedal to frame
Brake disc to wheel
Tighening of union bolt
Master cylinder to frame
Tightening of air bleeder
Fuel system Fuel tank to fuel cock
NOTE:
Concerning the tightening torque, refer to “
MAINTENANCE SPECIFICATIONS” section in
the CHAPTER 2.
5XE-9-30-1B 3/24/03 11:06 PM Page 10

1-17
GEN
INFO
CLEANING AND STORAGE
EC1B0000
CLEANING AND STORAGE
EC1B1000
CLEANING
Frequent cleaning of your machine will enhance
its appearance, maintain good overall perfor-
mance, and extend the life of many components.
1. Before washing the machine, block off the
end of the exhaust pipe to prevent water
from entering. A plastic bag secured with a
rubber band may be used for this purpose.
2. If the engine is excessively greasy, apply
some degreaser to it with a paint brush. Do
not apply degreaser to the chain, sprockets,
or wheel axles.
3. Rinse the dirt and degreaser off with a gar-
den hose; use only enough pressure to do
the job.
cC
Excessive hose pressure may cause water
seepage and contamination of wheel bear-
ings, front forks, brakes and transmission
seals. Many expensive repair bills have re-
sulted from improper high pressure deter-
gent applications such as those available
in coin-operated car washers.
4. After the majority of the dirt has been hosed
off, wash all surfaces with warm water and a
mild detergent. Use an old toothbrush to
clean hard-to-reach places.
5. Rinse the machine off immediately with
clean water, and dry all surfaces with a soft
towel or cloth.
6. Immediately after washing, remove excess
water from the chain with a paper towel and
lubricate the chain to prevent rust.
7. Clean the seat with a vinyl upholstery clean-
er to keep the cover pliable and glossy.
8. Automotive wax may be applied to all paint-
ed or chromed surfaces. Avoid combination
cleaner-waxes, as they may contain abra-
sives.
9. After completing the above, start the engine
and allow it to idle for several minutes.
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2-2
SPECGENERAL SPECIFICATIONS
Carburetor:
Type/Manufacturer TMXχ
38SS/MIKUNI
Spark plug:
Type/Manufacturer BR9EG/NGK (resistance type)
Gap 0.5~0.6 mm (0.020~0.024 in)
Clutch type: Wet, multiple-disc
Transmission:
Primary reduction system Gear
Primary reduction ratio 64/19 (3.368)
Secondary reduction system Chain drive
Secondary reduction ratio 49/13 (3.769)
Transmission type Constant mesh, 5-speed
Operation Left foot operation
Gear ratio: 1st 30/13 (2.308)
2nd 28/15 (1.867)
3rd 29/19 (1.526)
4th 24/19 (1.263)
5th 25/23 (1.087)
Chassis:USA, ZA, AUS, NZEUROPE,CDN
Frame type Semi double cradle←
Caster angle 25.6° 25.4°
Trail 108 mm (4.25 in) 104 mm (4.09 in)
Tire:
Type With tube
Size (front) 80/100-21 51M
Size (rear) 100/90-19 57M
Tire pressure (front and rear) 100 kPa (1.0 kgf/cm2, 15 psi)
Brake:
Front brake type Single disc brake
Operation Right hand operation
Rear brake type Single disc brake
Operation Right foot operation
Suspension:
Front suspension Telescopic fork
Rear suspension Swingarm (link type monocross suspension)
Shock absorber:
Front shock absorber Coil spring/oil damper
Rear shock absorber Coil spring/Gas, oil damper
Wheel travel:
Front wheel travel 300 mm (11.8 in)
Rear wheel travel 315 mm (12.4 in)
Electrical:
Ignition system CDI magneto
2
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2-5
SPECMAINTENANCE SPECIFICATIONS
Part to be tightened Thread size Q'tyT ightening torqueNm m•kg ft•lb
Spark plug M14 ×1.25 1 20 2.0 14
Cylinder head (nut) M 8 ×1.25 5 28 2.8 20
(stud) M 8 ×1.25 5 13 1.3 9.4
Cylinder (nut) M 8 ×1.25 4 30 3.0 22
(stud) M10 ×1.25 4 13 1.3 9.4
Power valve:
Cover M 5 ×0.8 4 4 0.4 2.9
Link lever M 4 ×0.7 1 4 0.4 2.9
Holder (power valve) M 5 ×0.8 4 8 0.8 5.8
Push rod M 5 ×0.8 1 5 0.5 3.6
Thrust plate M 5 ×0.8 1 4 0.4 2.9
Governor fork M 4 ×0.7 2 5 0.5 3.6
Housing M 5 ×0.8 4 5 0.5 3.6
Impeller M 8 ×1.25 1 14 1.4 10
Water pump housing cover M 6 ×1.0 4 10 1.0 7.2
Coolant drain bolt M 6 ×1.0 1 10 1.0 7.2
Radiator M 6 ×1.0 6 10 1.0 7.2
Radiator panel M 6 ×1.0 2 10 1.0 7.2
Radiator hose clamp M 6 ×1.0 8 1 0.1 0.7
Air filter element M 6 ×1.0 1 2 0.2 1.4
Carburetor joint M 6 ×1.0 4 10 1.0 7.2
Air filter case M 6 ×1.0 4 8 0.8 5.8
Air filter guide clamp M 5 ×0.8 1 1 0.1 0.7
Read valve M 3 ×0.5 6 1 0.1 0.7
Crankcase M 6 ×1.0 12 14 1.4 10
Crankcase cover (right) M 6 ×1.0 8 10 1.0 7.2
Crankcase cover (left) M 6 ×1.0 5 5 0.5 3.6
Chain cover M 6 ×1.0 2 5 0.5 3.6
Bearing plate cover M 6 ×1.0 3 10 1.0 7.2
Holder M 6 ×1.0 1 10 1.0 7.2
Oil check bolt M 6 ×1.0 1 10 1.0 7.2
Oil drain bolt M12 ×1.5 1 20 2.0 14
Kick starter M 6 ×1.0 1 10 1.0 7.2
Cluch cover M 6 ×1.0 6 10 1.0 7.2
Primary drive gear M10 ×1.25 1 55 5.5 40
Clutch boss M16 ×1.0 1 80 8.0 58
Clutch spring M 6 ×1.0 5 10 1.0 7.2
Push lever axle M 6 ×1.0 1 7 0.7 5.1
Drive sprocket M16 ×1.0 1 65 6.5 47
Shift pedal M 6 ×1.0 1 12 1.2 8.7
Bearing plate cover (shift cam) M 6 ×1.0 2 10 1.0 7.2
Shift guide M 6 ×1.0 2 10 1.0 7.2
Stopper lever M 6 ×1.0 1 10 1.0 7.2
Segment M 8 ×1.25 1 30 3.0 22
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2-7
SPECMAINTENANCE SPECIFICATIONS
EC212201
CHASSIS
Item Standard Limit
Steering system:
Steering bearing type Taper roller bearing…
Front suspension:
Front fork travel 300 mm (11.8 in)…
Fork spring free length 479 mm (18.9 in) 474 mm (18.7 in)
Spring rate, STD K=4.0 N/mm…
(0.408 kg/mm, 22.8 lb/in)
Optional spring/Spacer Yes…
Oil capacity 662 cm
3…
(23.3 Imp oz, 22.38 US oz)
Oil level 125 mm (4.92 in)…
105~135 mm (4.13~5.31 in)…
(From top of outer tube with inner tube
and damper rod fully compressed
without spring.)
Oil grade Suspension oil “01”…
Inner tube outer diameter 48 mm (1.89 in)…
Front fork top end 5 mm (0.20 in)…
Rear suspension: USA, CDN, ZA
EUROPE
AUS, NZ
Shock absorber travel
132 mm (5.20 in)←…
Spring free length
260 mm (10.24 in) 275 mm (10.83 in)…
Fitting length
248 mm (9.76 in)265 mm (10.43 in)…

240.5~258.5 mm 255.5~273.5 mm…
(9.47~10.18 in)
(10.06~10.77 in)
Spring rate, STD K=44.0 N/mm K=Approx.…
(4.50 kg/mm, 46.0 N/mm
252.0 lb/in) (4.70 kg/mm,
263.2 lb/in)
Optional spring Yes←…
Enclosed gas pressure 1,000 kPa ←…
(10 kg/cm
2,
142 psi)
Swingarm:
Swingarm free play limit
End…
1.0 mm (0.04 in)
Side clearance…
0.2~0.9 mm
(0.008~0.035 in)
5XE-9-30-2A 5/10/03 1:57 PM Page 8