wheel YAMAHA WR 250F 2008 Owner's Manual

5-45
KICK SHAFT AND SHIFT SHAFT
REMOVING THE KICK SHAFT
ASSEMBLY
1. Remove:• Kick shaft assembly "1"
Unhook the torsion spring "2" from
the hole "a" in the crankcase.
REMOVING THE SHIFT GUIDE
AND SHIFT LEVER ASSEMBLY
1. Remove:• Bolt (shift guide)
• Shift guide "1"
• Shift lever assembly "2"
The shift lever assembly is disassem-
bled at the same time as the shift
guide.
REMOVING THE SEGMENT
1. Remove:
• Bolt (segment) "1"
• Segment "2"
Turn the segment counterclockwise
until it stops and loosen the bolt.
If the segment gets an impact, it
may be damaged. Take care not to
give an impact to the segment
when removing the bolt.
CHECKING THE KICK SHAFT AND
RATCHET WHEEL
1. Check:• Ratchet wheel "1" smooth move-
ment
Unsmooth movement →Replace. • Kick shaft "2"
Wear/damage →Replace.
• Spring "3" Broken →Replace.
CHECKING THE KICK GEAR, KICK
IDLE GEAR AND RATCHET
WHEEL
1. Inspect: • Kick gear "1"
• Kick idle gear "2"
• Ratchet wheel "3"
• Gear teeth "a"
• Ratchet teeth "b"Wear/damage →Replace.
CHECKING THE SHIFT SHAFT
1. Inspect: • Shift shaft "1"
Bend/damage →Replace.
• Spring "2" Broken →Replace.
CHECKING THE SHIFT GUIDE AND
SHIFT LEVER ASSEMBLY
1. Inspect: • Shift guide "1"
• Shift lever "2"
• Pawl "3"
• Pawl pin "4"
• Spring "5"Wear/damage →Replace. CHECKING THE STOPPER LEVER
1. Inspect:
• Stopper lever "1"Wear/damage →Replace.
• Torsion spring "2" Broken →Replace.
INSTALLING THE SEGMENT
1. Install: • Segment "1"
• Bolt (segment)
Align the notch "a" on the segment
with the pin "b" on the shift cam.
If the segment gets an impact, it
may be damaged. Take care not to
give an impact to the segment
when tightening the bolt.
INSTALLING THE STOPPER
LEVER
1. Install:• Torsion spring "1"
• Stopper lever "2"
• Bolt (stopper lever) "3"
Align the stopper lever roller with the
slot on segment.
Bolt (segment): 30 Nm (3.0 m•kg, 22
ft•lb)
Bolt (stopper lever): 10 Nm (1.0 m•kg, 7.2
ft•lb)

5-46
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 TH
E 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 pedalRefer to "AC MAGNETO AND
STARTER CLUTCH" section.
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.
5. Hook:• Torsion spring "1"
Turn the torsion spring clockwise and
hook into the proper hole "a" in the
crankcase.Bolt (shift guide):
10 Nm (1.0 m•kg, 7.2
ft•lb)

5-64
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 movementUnsmooth 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 (19T) "1"
• 3rd pinion gear (17T) "2"
• Collar "3"
• 4th pinion gear (21T) "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 (23T) "2"
• 3rd wheel gear (23T) "3"
• 5th wheel gear (17T) "4"
• 1st wheel gear (31T) "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.

5-65
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 operation
Unsmooth operation →Repair.

6-1
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
5 Speed sensor 1
6 Collar 1
7 Oil seal 1
8 Bearing 2 Refer to removal section.
9 Brake disc 1
21 Nm (2.1 m kg, 15 ft lb)
21 Nm (2.1 m kg, 15 ft lb)
12 Nm (1.2 m kg, 8.7 ft lb)
90 Nm (9.0 m kg, 65 ft lb)

6-2
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.
5 Collar 2
6 Rear wheel sprocket 1
7 Oil seal 2
8 Circlip 1
9 Bearing 2 Refer to removal section.
10 Brake disc 1
125 Nm (12.5 m kg, 90 ft lb)
14 Nm (1.4 m kg, 10 ft lb)
19 Nm (1.9 m kg, 13 ft lb)
19 Nm (1.9 m kg, 13 ft lb)
50 Nm (5.0 m kg, 36 ft lb)
6

6-3
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.
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)

6-4
FRONT WHEEL AND REAR WHEEL
2. Install:• Brake disc "1"
• 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.
4. Install:• Speed sensor "1"
• Apply the lithium soap base grease on the oil seal lip of the speed sen-
sor.
• Make sure the two projections "a" in the wheel hub are meshed with the
two slots "b" in the speed sensor.
5. Install:• Wheel
• Install the brake disc "1" between
the brake pads "2" correctly.
• Make sure that the projections "a" in the speed sensor fits over the stop-
per "b" on the front fork inner tube.
6. Install:• Wheel axle "1"
Apply the lithium soap base grease
on the wheel axle.
7. Install:• Nut (wheel axle) "1"
8. 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.
Bolt (brake disc): 12 Nm (1.2 m•kg, 8.7
ft•lb)
Nut (wheel axle):
90 Nm (9.0 m•kg, 65
ft•lb)
Bolt (axle holder): 21 Nm (2.1 m•kg, 15
ft•lb)

6-5
FRONT WHEEL AND REAR WHEEL
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.
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"
Bolt (brake disc):
14 Nm (1.4 m•kg, 10
ft•lb)
Nut (rear wheel sprock-
et): 50 Nm (5.0 m•kg, 36
ft•lb)
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)

6-7
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
5 Brake hose 1
6 Pad pin plug 1 Remove when loosening the pad pin.
7Pad pin 1Loosen when disassembling the brake cali-
per.
8 Brake caliper 1