wheel YAMAHA YZ250F 2008 Owner's Manual

4-47
KICK SHAFT AND SHIFT SHAFT
INSTALLING THE SHIFT GUIDE
AND SHIFT LEVER ASSEMBLY
1. Install:• Spring "1"
• Pawl pin "2"
•Pawl "3"To shift lever "4".
Apply the engine oil on the spring,
pawl pin and pawl.
2. Install:• Shift lever assembly "1"
To shift guide "2".
3. Install: • Shift lever assembly "1"
• Shift guide "2"
• The shift lever assembly is installed
at the same time as the shift guide.
• Apply the engine oil on the bolt
(segment) shaft.
4. Install:• Bolt (shift guide) "1" INSTALLING THE SHIFT SHAFT
1. Install:
•Roller "1"
•Collar "2"
• Torsion spring "3"
• Shift shaft "4"
Apply the engine oil on the roller and
shift shaft.
2. Install:• Shift pedal "1"
• Bolt (shift pedal) "2"
When installing the shift pedal onto
the shift shaft, be sure that the center
of the shift pedal is about 0 mm (0 in)
"a" above the top of the footrest.
INSTALLING THE KICK SHAFT
ASSEMBLY
1. Install:• Kick gear "1"
•Washer "2"
•Circlip "3"
• Ratchet wheel "4"
• Spring "5"
•Washer "6"
•Circlip "7" To kick shaft "8".
• Apply the molybdenum disulfide oil
on the inner circumferences of the
kick gear and ratchet wheel.
• Align the punch mark "a" on the
ratchet wheel with the punch mark
"b" on the kick shaft.
2. Install:• Torsion spring "1"To kick shaft "2".
Make sure the stopper "a" of the tor-
sion spring fits into the hole "b" on the
kick shaft.
3. Install:• Spring guide "1"
Slide the spring guide into the kick
shaft, make sure the groove "a" in the
spring guide fits on the stopper of the
torsion spring.
4. Install:
• Kick shaft assembly "1"
• Washer "2"
• Apply the molybdenum disulfide grease on the contacting surfaces
of the kick shaft stopper "a" and kick
shaft ratchet wheel guide "3".
• Apply the engine oil on the kick shaft.
• Slide the kick shaft assembly into
the crankcase and make sure the
kick shaft stopper "a" fits into the
kick shaft ratchet wheel guide.
Bolt (shift guide): 10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (shift pedal):12 Nm (1.2 m•kg, 8.7
ft•lb)

4-50
CDI MAGNETO
REMOVING THE ROTOR
1. Remove:• Nut (rotor) "1"
• Washer "2"Use the rotor holding tool "3".
2. Remove: • Rotor "1"Use the flywheel puller "2".
When installing the flywheel puller,
turn it counterclockwise.
CHECKING THE CDI MAGNETO
1. Inspect:• Rotor inner surface "a"
• Stator outer surface "b"
Damage
→Inspect the crankshaft
runout and crankshaft bearing.
If necessary, replace CDI magne-
to and/or stator.
CHECKING THE WOODRUFF KEY
1. Inspect: • Woodruff key "1"Damage
→Replace. INSTALLING THE CDI MAGNETO
1. Install:
•Stator "1"
• Screw (stator) "2"
• Apply the sealant on the grommet of the CDI magneto lead.
• Tighten the screws using the T30 bit.
2. Install:
• Woodruff key "1"
•Rotor "2"
• Clean the tapered portions of the crankshaft and rotor.
• When installing the woodruff key, make sure that its flat surface "a" is
in parallel with the crankshaft center
line "b".
• When installing the rotor, align the keyway "c" of the rotor with the
woodruff key.
3. Install:•Washer "1"
• Nut (rotor) "2"
Use the rotor holding tool "3". 4. Connect:
• CDI magneto leadRefer to "CABLE ROUTING DIA-
GRAM" section in the CHAPTER
2.
5. Install: • Dowel pin
• Gasket (left crankcase cover)
• Left crankcase cover "1"
• Hose guide (cylinder head breath-er hose) "2"
• Bolt (left crankcase cover)
Tighten the bolts in stage, using a
crisscross pattern.
Rotor holding tool:
YU-1235/90890-01235
Flywheel puller: YM-1189/90890-01189
Screw (stator):
10 Nm (1.0 m•kg,
7.2ft•lb)
YAMAHA Bond No. 1215
(ThreeBond
® No. 1215):
90890-85505
Nut (rotor): 56 Nm (5.6 m•kg, 40
ft•lb)
Rotor holding tool: YU-1235/90890-01235
Bolt (left crankcase cov-
er):10 Nm (1.0 m•kg, 7.2
ft•lb)

4-62
TRANSMISSION, SHIFT CAM AND SHIFT FORK
REMOVING THE TRANSMISSION
1. Remove:• Main axle "1"
•Drive axle "2"
•Shift cam
• Shift fork 3
• Shift fork 2
• Shift fork 1
• Remove assembly with the collar "3" installed to the crankcase.
• Remove assembly carefully. Note
the position of each part. Pay partic-
ular attention to the location and di-
rection of shift forks.
• Remove the main axle, drive axle, shift cam and shift fork all together
by tapping lightly on the transmis-
sion drive axle with a soft hammer.
CHECKING THE 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.
CHECKING THE BEARING
1. Inspect: • Bearing "1"
Rotate inner race with a finger.
Rough spot/seizure
→Replace. CHECKING THE SHIFT FORK,
SHIFT CAM AND SEGMENT
1. Inspect:
• Shift fork "1"
Wear/damage/scratches
→Re-
place.
2. Inspect: • Shift cam "1"
• Segment "2"Wear/damage
→Replace.
3. Check: • Shift fork movement
Unsmooth operation
→Replace
shift fork.
For a malfunctioning shift fork, re-
place not only the shift fork itself but
the two gears each adjacent to the
shift fork.
INSTALLING THE TRANSMISSION
1. Install: • 5th pinion gear (24T) "1"
• 3rd pinion gear (20T) "2"
•Collar "3"
• 4th pinion gear (22T) "4"
• 2nd pinion gear (16T) "5"To main axle "6".
Apply the molybdenum disulfide oil
on the inner and end surface of the idler gear and on the inner surface of
the sliding gear, then install.
2. Install:
• 2nd wheel gear (28T) "1"
• 4th wheel gear (27T) "2"
• 3rd wheel gear (29T) "3"
• 5th wheel gear (25T) "4"
• 1st wheel gear (30T) "5"
• O-ring "6" To drive axle "7".
• Apply the molybdenum disulfide oil on the inner and end surface of the
idler gear and on the inner surface
of the sliding gear, then install.
• Apply the lithium soap base grease on the O-ring.
3. Install:
• Washer "1"
• Circlip "2"
• Be sure the circlip sharp-edged cor-ner "a" is positioned opposite side
to the washer and gear "b".
• Install the circlip with its ends "c" settled evenly on the spline crests.

4-63
TRANSMISSION, SHIFT CAM AND SHIFT FORK
4. Install:•Collar "1"
• Apply the lithium soap base grease on the oil seal lip.
• When installing the collar into the crankcase, pay careful attention to
the crankcase oil seal lip.
5. Install:• Shift fork 1 (L) "1"
• Shift fork 2 (C) "2"
• Shift fork 3 (R) "3"
•Shift cam "4"To main axle and drive axle.
• Apply the molybdenum disulfide oil on the shift fork grooves.
• Mesh the shift fork #1 (L) with the 4th wheel gear "5" and #3 (R) with
the 5th wheel gear "7" on the drive
axle.
• Mesh the shift fork #2 (C) with the 3rd pinion gear "6" on the main ax-
le.
6. Install:• Transmission assembly "1"
To left crankcase "2".
Apply the engine oil on the bearings
and guide bars.
7. Check:• Shifter operation
• Transmission operationUnsmooth operation
→Repair.

5-1
FRONT WHEEL AND REAR WHEEL
CHASSIS
FRONT WHEEL AND REAR WHEEL
REMOVING THE FRONT WHEELOrder Part name Q'ty Remarks Hold the machine by placing the suitable stand
under the engine. Refer to "HANDLING NOTE".
1 Bolt (axle holder) 4 Only loosening.
2 Nut (front wheel axle) 1
3 Front wheel axle 1
4 Front wheel 1
5Collar 2
6 Oil seal 2
7 Bearing 2 Refer to removal section.
8Brake disc 1
5

5-2
FRONT WHEEL AND REAR WHEEL
REMOVING THE REAR WHEELOrder Part name Q'ty Remarks Hold the machine by placing the suitable stand
under the engine. Refer to "HANDLING NOTE".
1 Nut (rear wheel axle) 1
2 Rear wheel axle 1
3 Drive chain puller 2
4 Rear wheel 1 Refer to removal section.
5Collar 2
6 Rear wheel sprocket 1
7 Oil seal 2
8 Circlip 1
9 Bearing 2 Refer to removal section.
10 Brake disc 1

5-3
FRONT WHEEL AND REAR WHEEL
HANDLING NOTE
Support the machine securely so
there is no danger of it falling over.
REMOVING THE REAR WHEEL
1. Remove:• Wheel "1"
Push the wheel forward and remove
the drive chain "2".
REMOVING THE WHEEL BEARING
1. Remove:• Bearing "1"
Remove the bearing using a general
bearing puller "2".
CHECKING THE WHEEL
1. Measure:• Wheel runout
Out of limit
→ Repair/replace.
2. Inspect: • BearingRotate inner race with a finger.
Rough spot/seizure
→ Replace.
Replace the bearings, oil seal and
wheel collar as a set.
CHECKING THE WHEEL AXLE
1. Measure:• Wheel axle bendsOut 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
axle.
CHECKING THE BRAKE DISC
1. Measure: • Brake disc deflection (only rear
brake disc)
Use the dial gauge "1".
Out of specification
→ Inspect
wheel runout.
If wheel runout is in good condi-
tion, replace the brake disc.
2. Measure: • Brake disc thickness "a"
Out of limit
→ Replace. INSTALLING THE FRONT WHEEL
1. Install:
• Bearing (left) "1"
•Spacer "2"
• Bearing (right) "3"
•Oil seal "4"
• Apply the lithium soap base grease on the bearing and oil seal lip when
installing.
• Use a socket that matches the out- side diameter of the race of the
bearing.
• Left side of bearing shall be in- stalled first.
• Install the oil seal with its manufac-
ture's marks or numbers facing out-
ward.
Do not strike the inner race of the
bearing. Contact should be made
only with the outer race.
2. Install:• Brake disc "1"
Wheel runout limit:
Radial "1": 2.0 mm
(0.08 in)
Lateral "2": 2.0 mm
(0.08 in)
Wheel axle bending limit:0.5 mm (0.020 in)
Brake disc deflection lim-
it: Rear:
: 0.15 mm
(0.006 in)
Brake disc thickness: Front:3.0 mm (0.12 in)
: 2.5 mm (0.10
in)
Rear:
4.0 mm (0.16 in)
: 3.5 mm (0.14
in)

5-4
FRONT WHEEL AND REAR WHEEL
• Bolt (brake disc) "2"
Tighten the bolts in stage, using a
crisscross pattern.
3. Install:•Collar "1"
• Apply the lithium soap base grease on the oil seal lip.
• Install the collars with their projec- tions "a" facing the wheel.
4. Install:• Wheel
• Install the brake disc "1" between
the brake pads "2" correctly.
5. Install:• Wheel axle "1"
Apply the lithium soap base grease
on the wheel axle.
6. Install:• Nut (wheel axle) "1" 7. Tighten:
• Bolt (axle holder) "1"
Before tightening the bolt, fit the
wheel axle to the axle holder by strok-
ing the front fork several times with
the front brake applied.
INSTALLING THE REAR WHEEL
1. Install:
• Bearing (right) "1"
•Circlip "2"
•Spacer "3"
• Bearing (left) "4"
• Oil seal "5"
• Apply the lithium soap base grease on the bearing and oil seal lip when
installing.
• Install the bearing with seal facing
outward.
• Use a socket that matches the out- side diameter of the race of the
bearing.
• Right side of bearing shall be in- stalled first.
• Install the oil seal with its manufac- ture's marks or numbers facing out-
ward.
Do not strike the inner race of the
bearing. Contact should be made
only with the outer race.
2. Install:• Brake disc "1"
• Bolt (brake disc) "2"
Tighten the bolts in stage, using a
crisscross pattern.
3. Install:• Rear wheel sprocket "1"
• Bolt (rear wheel sprocket) "2"
• Washer (rear wheel sprocket) "3"
• Nut (rear wheel sprocket) "4"
Tighten the nuts in stage, using a
crisscross pattern.
Bolt (brake disc): 12 Nm (1.2 m•kg, 8.7
ft•lb)Nut (wheel axle):105 Nm (10.5 m•kg, 75
ft•lb)
Bolt (axle holder): 21 Nm (2.1 m•kg, 15
ft•lb)
Bolt (brake disc):14 Nm (1.4 m•kg, 10
ft•lb)
Nut (rear wheel sprock-
et): 42 Nm (4.2 m•kg, 30
ft•lb)

5-5
FRONT WHEEL AND REAR WHEEL
4. Install:•Collar "1"
Apply the lithium soap base grease
on the oil seal lip.
5. Install:• Wheel
Install the brake disc "1" between the
brake pads "2" correctly.
6. Install:• Drive chain "1"
Push the wheel "2" forward and install
the drive chain.
7. Install:• Left drive chain puller "1"
• Wheel axle "2"
• Install the left drive chain puller, and
insert the wheel axle from left side.
• Apply the lithium soap base grease
on the wheel axle.
8. Install:• Right drive chain puller "1"
• Washer "2"
• Nut (wheel axle) "3"
Temporarily tighten the nut (wheel
axle) at this point.
9. Adjust:
• Drive chain slack "a"
Refer to "ADJUSTING THE
DRIVE CHAIN SLACK" section in
the CHAPTER 3.
10. Tighten: • Nut (wheel axle) "1"
• Locknut "2"
Drive chain slack: 48–58 mm (1.9–2.3 in)
Nut (wheel axle): 125 Nm (12.5 m•kg, 90
ft•lb)
Locknut: 19 Nm (1.9 m•kg, 13
ft•lb)

5-7
FRONT BRAKE AND REAR BRAKE
REMOVING THE REAR BRAKEOrder Part name Q'ty Remarks Hold the machine by placing the suitable stand
under the engine. Refer to "HANDLING NOTE".
Rear wheel Refer to "FRONT WHEEL AND REAR
WHEEL" section.
Drain the brake fluid. Refer to removal section.
1 Brake pedal 1
2 Brake master cylinder 1
3 Brake hose holder 2
4 Union bolt 2
5Brake hose 1
6 Pad pin plug 1 Remove when loosening the pad pin.
7 Pad pin 1Loosen when disassembling the brake cali-
per.
8 Brake caliper 1