Fork YAMAHA YZ250F 2003 User Guide

3 - 4
INSP
ADJ
PRE-OPERATION INSPECTION AND MAINTENANCE
EC320000
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating
condition.
Before using this machine, check the following points.
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
CoolantCheck that coolant is filled up to the radiator cap.
Check the cooling system for leakage.P.3-5 ~ 9
FuelCheck that a fresh gasoline is filled in the fuel tank. Check the
fuel line for leakage.P.1-13
Engine oilCheck that the oil level is correct. Check the crankcase and
frame oil line for leakage.P.3-13 ~ 16
Gear shifter and clutchCheck that gears can be shifted correctly in order and that the
clutch operates smoothly.P.3-9
Throttle grip/HousingCheck that the throttle grip operation and free play are correctly
adjusted. Lubricate the throttle grip and housing, if necessary.P.3-10
Brakes Check the play of front brake and effect of front and rear brake. P.3-24 ~ 30
Drive chainCheck drive chain slack and alignment. Check that the drive
chain is lubricated properly.P.3-31 ~ 33
WheelsCheck for excessive wear and tire pressure. Check for loose
spokes and have no excessive play.P.3-41 ~ 42
SteeringCheck that the handlebar can be turned smoothly and have no
excessive play.P.3-42 ~ 43
Front forks and rear shock
absorberCheck that they operate smoothly and there is no oil leakage. P.3-33 ~ 40
Cables (wires)Check that the clutch and throttle cables move smoothly. Check
that they are not caught when the handlebars are turned or
when the front forks travel up and down.—
Exhaust pipeCheck that the exhaust pipe is tightly mounted and has no
cracks.P.4-3
Rear wheel sprocket Check that the rear wheel sprocket tightening bolt is not loose. P.3-31
Lubrication Check for smooth operation. Lubricate if necessary. P.3-44
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P.1-18
Lead connectorsCheck that the CDI magneto, CDI unit, and ignition coil are con-
nected tightly.P.1-6
SettingsIs the machine set suitably for the condition of the racing course
and weather or by taking into account the results of test runs
before racing? Are inspection and maintenance completely
done?P.7-1 ~ 22

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INSP
ADJ
FRONT BRAKE PAD INSPECTION AND REPLACEMENT
Loosen the pad pin 2.
Remove the brake hose holder 3 and
brake caliper 4 from the front fork.
Remove the pad pin and brake pads 5.
Connect the transparent hose 6 to the
bleed screw 7 and place the suitable con-
tainer under its end.
Loosen the bleed screw and push the
brake caliper piston in.
CAUTION:
Do not reuse the drained brake fluid.
Tighten the bleed screw.
T R..
Bleed screw:
6 Nm (0.6 m • kg, 4.3 ft • lb)
Install the brake pads 8 and pad pin.
NOTE:
Install the brake pads with their projec-
tions a into the brake caliper recesses b.
Temporarily tighten the pad pin at this
point.
Install the brake hose holder 9 and brake
caliper 0 and tighten the pad pin A.
NOTE:
Fit the brake hose holder cut c over the
projection d on the front fork and clamp the
brake hose.
T R..
Bolt (brake caliper):
23 Nm (2.3 m • kg, 17 ft • lb)
Pad pin:
18 Nm (1.8 m • kg, 13 ft • lb)

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INSP
ADJ
FRONT FORK INSPECTION
3. Adjust:
Drive chain slack
Drive chain slack adjustment steps:
Loosen the axle nut 1 and locknuts 2.
Adjust the drive chain slack by turning the
adjusters 3.
To tighten → Turn the adjuster 3 coun-
terclockwise.
To loosen → Turn the adjuster 3 clock-
wise and push wheel forward.
Turn each adjuster exactly the same
amount to maintain correct axle alignment.
(There are marks a on each side of the
drive chain puller alignment.)
NOTE:
Turn the adjuster so that the drive chain is in
line with the sprocket, as viewed from the
rear.
CAUTION:
Too small drive chain slack will overload
the engine and other vital parts; keep the
slack within the specified limits.
Tighten the axle nut while pushing down
the drive chain.
T R..
Axle nut:
125 Nm (12.5 m • kg, 90 ft • lb)
Tighten the locknuts.
T R..
Locknut:
16 Nm (1.6 m • kg, 11 ft • lb)
EC36C000
FRONT FORK INSPECTION
1. Inspect:
Front fork smooth action
Operate the front brake and stroke the
front fork.
Unsmooth action/oil leakage → Repair
or replace.

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INSP
ADJFRONT FORK OIL SEAL AND DUST SEAL CLEANING/
FRONT FORK INTERNAL PRESSURE RELIEVING/
FRONT FORK REBOUND DAMPING FORCE ADJUSTMENT
EC36D001
FRONT FORK OIL SEAL AND DUST SEAL
CLEANING
1. Remove:
Protector
Dust seal 1
NOTE:
Use a thin screw driver, and be careful not to
damage the inner fork tube and dust seal.
2. Clean:
Dust seal a
Oil seal b
NOTE:
Clean the dust seal and oil seal after every
run.
Apply the lithium soap base grease on the
inner tube.
FRONT FORK INTERNAL PRESSURE
RELIEVING
NOTE:
If the front fork initial movement feels stiff dur-
ing a run, relieve the front fork internal pres-
sure.
1. Elevate the front wheel by placing a suit-
able stand under the engine.
2. Remove the air bleed screw 1 and
release the internal pressure from the
front fork.
3. Install:
Air bleed screw
EC36H002
FRONT FORK REBOUND DAMPING FORCE
ADJUSTMENT
1. Adjust:
Rebound damping force
By turning the adjuster 1.
Stiffer a → Increase the rebound damp-
ing force. (Turn the adjuster 1 in.)
Softer b → Decrease the rebound damp-
ing force. (Turn the adjuster 1 out.)
T R..1 Nm (0.1 m · kg, 0.7 ft · lb)

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INSP
ADJFRONT FORK COMPRESSION DAMPING FORCE
ADJUSTMENT
STANDARD POSITION:
This is the position which is back by the spe-
cific number of clicks from the fully turned-in
position.
CAUTION:
Do not force the adjuster past the minimum
or maximum extent of adjustment. The
adjuster may be damaged.
WARNING
Always adjust each front fork to the same
setting. Uneven adjustment can cause poor
handling and loss of stability.
Extent of adjustment
Maximum Minimum
Fully turned in
position20 clicks out (from
maximum posi-
tion)
Standard position:
13 clicks out
EC36J001
FRONT FORK COMPRESSION DAMPING
FORCE ADJUSTMENT
1. Remove:
Rubber cap
2. Adjust:
Compression damping force
By turning the adjuster 1.
Stiffer a → Increase the compression
damping force. (Turn the adjuster 1
in.)
Softer b → Decrease the compression
damping force. (Turn the adjuster 1
out.)

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INSP
ADJ
REAR SHOCK ABSORBER INSPECTION
Extent of adjustment
Maximum Minimum
Fully turned in
position20 clicks out
(from maximum
position)
STANDARD POSITION:
This is the position which is back by the spe-
cific number of clicks from the fully turned-in
position.
* For EUROPE
CAUTION:
Do not force the adjuster past the minimum
or maximum extent of adjustment. The
adjuster may be damaged.
WARNING
Always adjust each front fork to the same
setting. Uneven adjustment can cause poor
handling and loss of stability.
3. Install:
Rubber cap
T R..
Standard position:
12 clicks out
* 10 clicks out
EC36K000
REAR SHOCK ABSORBER INSPECTION
1. Inspect:
Swingarm smooth action
Abnormal noise/unsmooth action →
Grease the pivoting points or repair the
pivoting points.
Damage/oil leakage → Replace.

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INSP
ADJ
STEERING HEAD INSPECTION AND ADJUSTMENT
2. Inspect:
Bearing free play
Exist play → Replace.
EC36U013
STEERING HEAD INSPECTION AND
ADJUSTMENT
1. Elevate the front wheel by placing a suit-
able stand under the engine.
2. Check:
Steering stem
Grasp the bottom of the forks and gen-
tly rock the fork assembly back and
forth.
Free play → Adjust steering head.
3. Check:
Steering smooth action
Turn the handlebar lock to lock.
Unsmooth action → Adjust steering ring
nut.
4. Adjust:
Steering ring nut
Steering ring nut adjustment steps:
Remove the number plate.
Remove the handlebar and handlebar
upper bracket.
Loosen the steering ring nut 1 using the
steering nut wrench 2.
Steering nut wrench:
YU-33975/90890-01403

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ENGCRANKCASE AND CRANKSHAFT
CRANKCASE BEARING
Extent of removal:1 Crankcase bearing removal
Extent of removal Order Part name Q’ty Remarks
CRANKCASE BEARING
REMOVAL
Preparation for removal Transmission
Shift cam and shift forkRefer to “TRANSMISSION, SHIFT
CAM AND SHIFT FORK” section.
1 Oil seal 2
2 Bearing 10 Refer to “REMOVAL POINTS”.
1

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ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H0000
TRANSMISSION, SHIFT CAM AND SHIFT FORK
Extent of removal:1 Shift fork, shift cam, main axle and drive axle removal
Extent of removal Order Part name Q’ty Remarks
TRANSMISSION, SHIFT CAM
AND SHIFT FORK REMOVAL
Preparation for removal Engine Refer to “ENGINE REMOVAL” section.
Separate the crankcase. Refer to “CRANKCASE AND CRANK-
SHAFT” section.
1 Main axle 1
Refer to “REMOVAL POINTS”. 2 Drive axle 1
3 Shift cam 1
4 Shift fork 3 1
5 Shift fork 2 1
6 Shift fork 1 1
7 Collar 1
1

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ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H3000
REMOVAL POINTS
EC4H3230
Transmission
1. Remove:
Main axle 1
Drive axle 2
Shift cam
Shift fork 3
Shift fork 2
Shift fork 1
NOTE:
Remove assembly with the collar 3 installed
to the crankcase.
Remove assembly carefully. Note the posi-
tion of each part. Pay particular attention to
the location and direction of shift forks.
Remove the main axle, drive axle, shift cam
and shift fork all together by tapping lightly
on the transmission drive axle with a soft
hammer.
EC4H4000
INSPECTION
EC4H4200
Gears
1. Inspect:
Matching dog a
Gear teeth b
Shift fork groove c
Wear/damage → Replace.
2. Inspect:
O-ring 1
Damage → Replace.
3. Check:
Gears movement
Unsmooth movement → Repair or
replace.
EC4H4600
Bearing
1. Inspect:
Bearing 1
Rotate inner race with a finger.
Rough spot/seizure → Replace.