YAMAHA YZ250F 2008 Owners Manual

5-19
FRONT FORK
CHECKING THE BASE VALVE
1. Inspect:• Base valve "1"Wear/damage
→Replace.
Contamination
→Clean.
• O-ring "2" Wear/damage
→Replace.
• Piston metal "3" Wear/damage
→Replace.
• Spring "4"
Damage/fatigue
→Replace base
valve.
• Air bleed screw "5"
Wear/damage
→Replace.
CHECKING THE COLLAR
1. Inspect: • Piston metal "1"Wear/damage
→Replace.
CHECKING THE FORK SPRING
1. Measure: • Fork spring free length "a"Out of specification
→Replace.
CHECKING THE INNER TUBE
1. Inspect: • Inner tube surface "a"Score marks
→Repair or replace.
Use #1,000 grit wet sandpaper.
Damaged oil lock piece
→Re-
place.
• Inner tube bends
Out of specification
→Replace. Use the dial gauge "1".
The bending value is shown by one
half of the dial gauge reading.
Do not attempt to straighten a bent
inner tube as this may dangerous-
ly weaken the tube.
CHECKING THE OUTER TUBE
1. Inspect:
• Outer tube "1"
Score marks/wear/damage
→Re-
place.
CHECKING THE ADJUSTER
1. Inspect: • Adjuster "1"
• O-ring "2"Wear/damage
→Replace.
ASSEMBLING THE FRONT FORK
1. Wash the all parts in a clean sol- vent.
2. Stretch the damper assembly ful- ly.
3. Fill: • Front fork oil "1"To damper assembly.
• Be sure to use recommended fork oil. If other oils are used,
they may have an excessively ad-
verse effect on the front fork per-
formance.
• Never allow foreign materials to enter the front fork.
4. After filling, pump the damper as- sembly "1" slowly up and down
(about 200 mm (7.9 in) stroke)
several times to bleed the damper
assembly of air.
Be careful not to excessive full stroke.
A stroke of 200 mm (7.9 in) or more
will cause air to enter. In this case, re-
peat the steps 2 to 4.
5. Measure:
• Oil level (left and right) "a"Out of specification
→ Adjust.
Fork spring free length:
454 mm (17.9 in)
<Limit>: 449 mm (17.7
in)
Inner tube bending limit:0.2 mm (0.008 in)
Recommended oil: Suspension oil "S1"
Oil capacity: 199 cm
3 (7.00 Imp oz,
6.73 US oz)
Standard oil level: 145-148 mm (5.71-5.83
in)
From top of fully
stretched damper as-
sembly.

5-20
FRONT FORK
6. Tighten:• Locknut "1"
Fully finger tighten the locknut onto
the damper assembly.
7. Loosen:• Compression damping adjuster "1"
• Loosen the compression damping adjuster finger tight.
• Record the set position of the ad- juster (the amount of turning out the
fully turned in position).
8. Install:• Base valve "1"To damper assembly "2".
First bring the damper rod pressure to
a maximum. Then install the base
valve while releasing the damper rod
pressure.
9. Check:• Damper assemblyNot fully stretched
→ Repeat the
steps 2 to 8.
10. Tighten: • Base valve "1"
Hold the damper assembly with the
cap bolt ring wrench "2" and use the
cap bolt wrench "3" to tighten the base valve with specified torque.
11. After filling, pump the damper as-
sembly "1" slowly up and down
more than 10 times to distribute
the fork oil.
12. While protecting the damper as- sembly "1" with a rag and com-
pressing fully, allow excessive oil
to overflow on the base valve
side.
Take care not to damage the damp-
er assembly.
13. Allow the overflowing oil to es-
cape at the hole "a" in the damper
assembly.
14. Check: • Damper assembly smooth move-
ment
Tightness/binding/rough spots

→
Repeat the steps 2 to 13. 15. Install:
• Dust seal "1"
• Stopper ring "2"
•Oil seal "3"
• Oil seal washer "4"
• Slide metal "5" To inner tube "6".
• Apply the fork oil on the inner tube.
• When installing the oil seal, use vi-
nyl seat "a" with fork oil applied to
protect the oil seal lip.
• Install the oil seal with its manufac- ture's marks or number facing the
axle holder side.
16. Install:• Piston metal "1"
Install the piston metal onto the slot
on inner tube.
Base valve: 29 Nm (2.9 m•kg, 21 ft•
lb)
Cap bolt wrench:
YM-01500/90890-01500
Cap bolt ring wrench: YM-01501/90890-01501

5-21
FRONT FORK
17. Install:• Outer tube "1"To inner tube "2".
18. Install: • Slide metal "1"
• Oil seal washer "2"To outer tube slot.
Press the slide metal into the outer
tube with fork seal driver "3".
19. Install:
•Oil seal "1"
Press the oil seal into the outer tube
with fork seal driver "2".
20. Install:• Stopper ring "1"
Fit the stopper ring correctly in the
groove in the outer tube.
21. Install:• Dust seal "1"
Apply the lithium soap base grease
on the inner tube.
22. Check:• Inner tube smooth movementTightness/binding/rough spots

→
Repeat the steps 15 to 21.
23. Measure: • Distance "a"Out of specification
→ Turn into
the locknut.
24. Install: •Collar "1"
• Fork spring "2"To damper assembly "3".
Install the collar with its larger dia.
end "a" facing the fork spring.
25. Install:• Damper assembly "1"To inner tube "2".
To install the damper assembly
into the inner tube, hold the inner
tube aslant. If the inner tube is held
vertically, the damper assembly
may fall into it, damaging the valve
inside.
26. Loosen:• Rebound damping adjuster "1"
• Loosen the rebound damping ad-
juster finger tight.
• Record the set position of the ad- juster (the amount of turning out the
fully turned in position).
27. Install:• Push rod "1"
• Copper washer "2"
•Adjuster "3"
To damper assembly "4".
• While compressing the inner tube "5", set the cap bolt ring wrench "7"
between the inner tube and locknut
"6".
• Fully finger tighten the adjuster onto the damper assembly.
Fork seal driver: YM-A0948/90890-01502
Fork seal driver: YM-A0948/90890-01502
Distance "a":
16 mm (0.63 in) or more
Between the damper
assembly "1" bottom
and locknut "2" bot-
tom.
Cap bolt ring wrench:YM-01501/90890-01501

5-22
FRONT FORK
28. Inspect:• Gap "a" between the adjuster "1" and locknut "2".
Out of specification
→ Retighten
and readjust the locknut.
If the adjuster is installed out of spec-
ification, proper damping force can-
not be obtained.
29. Tighten: • Adjuster (locknut) "1"
Hold the locknut "2" and tighten the
adjuster with specified torque.
30. Install:•Adjuster "1"
To inner tube. 31. Fill:
• Front fork oil "1"From outer tube top.
Never fail to make the oil amount
adjustment between the maximum
and minimum amount and always
adjust each front fork to the same
setting. Uneven adjustment can
cause poor handling and loss of
stability.
• Be sure to use recommended fork oil. If other oils are used,
they may have an excessively ad-
verse effect on the front fork per-
formance.
• Never allow foreign materials to enter the front fork.
32. Install:
• Damper assembly "1"To outer tube.
Temporarily tighten the damper as-
sembly.
33. Install:
• Protector guide "1" INSTALLING THE FRONT FORK
1. Install:
• Front fork "1"
• Temporarily tighten the pinch bolts (lower bracket).
• Do not tighten the pinch bolts (up- per bracket) yet.
2. Tighten:• Damper assembly "1"
Use the cap bolt ring wrench "2" to
tighten the damper assembly with
specified torque.
3. Adjust:• Front fork top end "a"
Gap "a" between the ad-
juster and locknut:
0.5–1.0 mm (0.02–0.04
in)
Adjuster (locknut): 29 Nm (2.9 m•kg, 21
ft•lb)
Adjuster: 55 Nm (5.5 m•kg, 40
ft•lb)
Recommended oil:Suspension oil "S1"
Standard oil amount: 330 cm
3 (11.6 Imp oz,
11.2 US oz)
Extent of adjustment: 300–375 cm
3
(10.6–13.2 Imp oz,10.1–
12.7 US oz)
Damper assembly:30 Nm (3.0 m•kg, 22
ft•lb)
Cap bolt ring wrench: YM-01501/90890-01501
Front fork top end (stan-
dard) "a": 5 mm (0.20 in)

5-23
FRONT FORK
4. Tighten:• Pinch bolt (upper bracket) "1"
• Pinch bolt (lower bracket) "2"
Tighten the lower bracket to speci-
fied torque. If torqued too much, it
may cause the front fork to mal-
function.
5. Install:• Protector "1"
• Bolt (protector) "2"
6. Adjust: • Rebound damping force
Turn in the damping adjuster "1" fin-
ger-tight and then turn out to the orig-
inally set position.
7. Adjust:
• Compression damping force
Turn in the damping adjuster "1" fin-
ger-tight and then turn out to the orig-
inally set position.Pinch bolt (upper brack-
et): 21 Nm (2.1 m•kg, 15
ft•lb)
Pinch bolt (lower brack-
et): 21 Nm (2.1 m•kg, 15
ft•lb)
Bolt (protector): 5 Nm (0.5 m•kg, 3.6
ft•lb)

5-24
HANDLEBAR
HANDLEBAR
REMOVING THE HANDLEBAROrder Part name Q'ty Remarks Number plate Remove the band only.
1 Hot starter cable 1 Disconnect at the lever side.
2 Hot starter lever holder 1
3 Clutch cable 1 Disconnect at the lever side.
4 Clutch lever holder 1
5 Engine stop switch 1
6 Brake master cylinder 1 Refer to removal section.
7 Throttle cable cap 1
8 Throttle cable #1 (pulled) 1 Disconnect at the throttle side.
9 Throttle cable #2 (pushed) 1 Disconnect at the throttle side.
10 Right grip 1 Refer to removal section.
11 Tube guide 1
12 Collar 1
13 Left grip 1 Refer to removal section.
14 Handlebar upper holder 2
15 Handlebar 1
16 Handlebar lower holder 2

5-25
HANDLEBAR
REMOVING THE BRAKE MASTER
CYLINDER
1. Remove:• Brake master cylinder bracket "1"
• Brake master cylinder "2"
• Do not let the brake master cylin-
der hang on the brake hose.
• Keep the brake master cylinder
cap side horizontal to prevent air
from coming in.
REMOVING THE GRIP
1. Remove:•Grip "1"
Blow in air between the handlebar or
tube guide and the grip. Then remove
the grip which has become loose.
CHECKING THE HANDLEBAR
1. Inspect:• Handlebar "1"
Bends/cracks/damage
→Re-
place.
Do not attempt to straighten a bent
handlebar as this may dangerous-
ly weaken the handlebar.
INSTALLING THE HANDLEBAR
1. Install: • Handlebar lower holder "1"
• Washer "2"
• Nut (handlebar lower holder) "3"
• Install the handlebar lower holder with its side having the greater dis- tance "a" from the mounting bolt
center facing forward.
• Apply the lithium soap base grease on the thread of the handlebar low-
er holder.
• Installing the handlebar lower hold- er in the reverse direction allows the
front-to-rear offset amount of the
handlebar position to be changed.
• Do not tighten the nut yet.
2. Install:
• Handlebar "1"
• Handlebar upper holder "2"
• Bolt (handlebar upper holder) "3"
• The handlebar upper holder should be installed with the punched mark
"a" forward.
• Install the handlebar so that the marks "b" are in place on both
sides.
• Install the handlebar so that the pro- jection "c" of the handlebar upper
holder is positioned at the mark on
the handlebar as shown.
• First tighten the bolts on the front side of the handlebar upper holder,
and then tighten the bolts on the
rear side.
3. Tighten:
• Nut (handlebar lower holder) "1"
4. Install: • Left grip "1"Apply the adhesive to the handle-
bar "2".
• Before applying the adhesive, wipe off grease or oil on the handlebar
surface "a" with a lacquer thinner.
• Install the left grip to the handlebar
so that the line "b" between the two
arrow marks faces straight upward.
Bolt (handlebar upper
holder): 28 Nm (2.8 m•kg, 20
ft•lb)
Nut (handlebar lower
holder):
34 Nm (3.4 m•kg, 24
ft•lb)

5-26
HANDLEBAR
5. Install:•Right grip "1"
•Collar "2"Apply the adhesive on the tube
guide "3".
• Before applying the adhesive, wipe
off grease or oil on the tube guide
surface "a" with a lacquer thinner.
• Install the grip to the tube guide so that the grip match mark "b" and
tube guide slot "c" form the angle as
shown.
6. Install:•Collar "1"
• Grip cap cover "2"
• Throttle grip "3"
Apply the lithium soap base grease
on the throttle grip sliding surface.
7. Install:
• Throttle cables "1"To tube guide "2".
Apply the lithium soap base grease
on the throttle cable end and tube
guide cable winding portion.
8. Install:
• Throttle cable cap "1"
• Screw (throttle cable cap) "2"
After tightening the screws, check
that the throttle grip "3" moves
smoothly. If it does not, retighten
the bolts for adjustment.
9. Install:• Grip cap cover "1"
• Cover (throttle cable cap) "2"
10. Install: • Brake master cylinder "1"
• Brake master cylinder bracket "2"
• Bolt (brake master cylinder brack-et) "3"
• Install the bracket so that the arrow mark "a" faces upward.
• First tighten the bolt on the upper
side of the brake master cylinder
bracket, and then tighten the bolt on
the lower side.
11. Install:• Engine stop switch "1"
• Clutch lever holder "2"
• Bolt (clutch lever holder) "3"
• Hot starter lever holder "4"
• Bolt (hot starter lever holder) "5"
•Clamp "6"
• The engine stop switch, clutch lever holder and clamp should be in-
stalled according to the dimensions
shown.
• Pass the engine stop switch lead in
the middle of the clutch lever hold-
er.
12. Install:• Clutch cable "1"
• Hot starter cable "2"
Apply the lithium soap base grease
on the clutch cable end and hot start-
er cable end.
Screw (throttle cable
cap): 4 Nm (0.4 m•kg, 2.9
ft•lb)
Bolt (brake master cylin-
der bracket): 9 Nm (0.9 m•kg, 6.5
ft•lb)
Bolt (clutch lever holder):
4 Nm (0.4 m•kg, 2.9
ft•lb)
Bolt (hot starter lever
holder): 4 Nm (0.4 m•kg, 2.9
ft•lb)

5-27
HANDLEBAR
13. Adjust:• Clutch lever free playRefer to "ADJUSTING THE
CLUTCH CABLE FREE PLAY"
section in the CHAPTER 3.
• Hot starter lever free play Refer to "ADJUSTING THE HOT
STARTER LEVER FREE PLAY"
section in the CHAPTER 3.

5-28
STEERING
STEERING
REMOVING THE STEERINGOrder Part name Q'ty Remarks TIGHTENING STEPS:
ŒTighten ring nut. 38 Nm (3.8 m•kg, 27 ft•lb)
ΠLoosen it one turn.
Œ Retighten it. 7 Nm (0.7 m•kg, 5.1 ft•lb)
Hold the machine by placing the suitable stand
under the engine. Refer to "HANDLING NOTE".
Number plate Refer to "SEAT, FUEL TANK AND SIDE
COVERS" section in the CHAPTER 4.
Handlebar Refer to "HANDLEBAR" section.
Front fender
1 Steering stem nut 1
2 Front fork 2 Refer to "FRONT FORK" section.
3 Upper bracket 1
4 Steering ring nut 1 Refer to removal section.
5 Lower bracket 1
6 Bearing race cover 1
7 Upper bearing 1
8 Lower bearing 1 Refer to removal section.