2010 YAMAHA YZ250F lock

4-39
BALANCER
REMOVING THE BALANCER
1. Straighten the lock washer tab.
2. Loosen:• Nut (primary drive gear) "1"
• Nut (balancer shaft driven gear) "2"
Place an aluminum plate "a" between
the teeth of the balancer shaft drive
gear "3" and driven gear "4".
3. Remove:• Balancer shaft "1"
When removing the balancer shaft,
align the center "a" of the balancer
shaft weight along the line connecting
the centers of the crankshaft and bal-
ancer shaft.
CHECKING THE PRIMARY DRIVE
GEAR, BALANCER SHAFT DRIVE
GEAR AND BALANCER SHAFT
DRIVEN GEAR
1. Inspect:
• Primary drive gear "1"
• Balancer shaft drive gear "2"
• Balancer shaft driven gear "3"Wear/damage →Replace. CHECKING THE BALANCER
SHAFT
1. Inspect:
• Balancer shaft
Cracks/damage →Replace.
INSTALLING THE BALANCER
1. Install: • Balancer shaft "1"
• Apply the engine oil on the bearing.
• When installing the balancer shaft, align the center "a" of the balancer
shaft weight along the line connect-
ing the centers of the crankshaft
and balancer shaft.
2. Install:• Balancer shaft driven gear "1"
Install the balancer shaft driven gear
onto the balancer shaft while aligning
the punch mark "a" on the balancer
shaft driven gear with the lower spline
"b" on the balancer shaft end.
3. Install:
• Balancer shaft drive gear "1"
• Align the punched mark "a" on the balancer shaft drive gear with the
punched mark "b" on the balancer
shaft driven gear "2".
• Align the punched mark "c" on the balancer shaft drive gear with the
lower spline "d" on the crankshaft
end.
4. Install:
• Lock washer "1"
• Nut (balancer shaft driven gear) "2"
• Primary drive gear "3"
• Lock washer "4"
• Nut (primary drive gear) "5"
• Install the primary drive gear with its stepped side "a" facing the engine.
• Place an aluminum plate "b" be- tween the teeth of the balancer
shaft drive gear "6" and driven gear
"7".
5. Bend the lock washer tab.
Nut (balancer shaft driv-
en gear): 50 Nm (5.0 m•kg, 36
ft•lb)
Nut (primary drive gear): 75 Nm (7.5 m•kg, 54
ft•lb)

4-46
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.
Bolt (segment): 30 Nm (3.0 m•kg, 22
ft•lb)

4-48
KICK SHAFT AND SHIFT SHAFT
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.
INSTALLING THE KICK IDLE
GEAR
1. Install:• Kick idle gear "1"
• Washer "2"
• Circlip "3"
• Apply the engine oil on the kick idle gear inner circumference.
• Install the kick idle gear with its de-
pressed side "a " toward you.

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 cr ankcase 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)

4-52
ENGINE REMOVAL
2 Neutral switch1
3 Drive chain sprocket cover 1
4 Nut (drive sprocket) 1 Refer to removal section.
5 Lock washer 1 Refer to removal section.
6 Drive sprocket 1 Refer to removal section.
7Clip 1
8 Bolt (brake pedal) 1
9 Brake pedal 1
10 Upper engine bracket 2
11 Front engine bracket 2
12 Engine mounting bolt 3
13 Pivot shaft 1 Refer to removal section.
14 Engine 1 Refer to removal section.
Order
Part name Q'tyRemarks

4-53
ENGINE REMOVAL
HANDLING NOTE
Support the machine securely so
there is no danger of it falling over.
REMOVING THE DRIVE
SPROCKET
1. Remove:• Nut (drive sprocket) "1"
• Lock washer "2"
• Straighten the lock washer tab.
• Loosen the nut while applying the rear brake.
2. Remove:• Drive sprocket "1"
• Drive chain "2"
Remove the drive sprocket together
with the drive chain.
REMOVING THE ENGINE
1. Remove:• Pivot shaft "1"
If the pivot shaft is pulled all the way
out, the swingarm will come loose. If
possible, insert a sh aft of similar di-
ameter into the other side of the swin-
garm to support it.
2. Remove:
• Engine "1"From right side.
Make sure that the couplers, hoses
and cables are disconnected.
INSTALLING THE ENGINE
1. Install:• Engine "1"
Install the engine from right side.
• Pivot shaft "2"
• Engine mounting bolt (lower) "3"
• Front engine bracket "4"
• Bolt (front engine bracket) "5"
• Patch "6"
• Engine mounting bolt (front) "7"
• Upper engine bracket "8"
• Bolt (upper engine bracket) "9"
• Engine mounting bolt (upper) "10" • Lower engine guard "11"
• Bolt (lower engine guard) "12"
• Apply the molybdenum disulfide
grease on the pivot shaft.
• Install the patch with the claw "a"
facing outside the chassis.
INSTALLING THE BRAKE PEDAL
1. Install:• Spring "1"
• Brake pedal "2"
• O-ring "3"
• Bolt (brake pedal) "4"
• Clip "5"
Apply the lithium soap base grease
on the bolt, O-rings and brake pedal
bracket.
Pivot shaft: 85 Nm (8.5 m•kg, 61
ft•lb)
Engine mounting bolt
(lower): 53Nm (5.3 m•kg, 38
ft•lb)
Bolt (front engine brack-
et): 34 Nm (3.4 m•kg, 24
ft•lb)
Engine mounting bolt
(front): 53 Nm (5.3 m•kg, 38
ft•lb)
Bolt (upper engine brack-
et): 34 Nm (3.4 m•kg, 24
ft•lb)
Engine mounting bolt
(upper): 55 Nm (5.5 m•kg, 40
ft•lb)
Bolt (lower engine
guard): 10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (brake pedal): 26 Nm (2.6 m•kg, 19
ft•lb)
M

4-54
ENGINE REMOVAL
INSTALLING THE DRIVE
SPROCKET
1. Install:• Drive sprocket "1"
• Drive chain "2"
Install the drive sprocket together
with the drive chain.
2. Install:
• Lock washer "1"
• Nut (drive sprocket) "2"
Tighten the nut while applying the
rear brake.
3. Bend the lock washer tab to lock the nut.
4. Install:
• Drive chain sprocket guide "1"
• Drive chain sp rocket cover "2"
• Bolt (drive chain sprocket cover)
"3" INSTALLING THE NEUTRAL
SWITCH
1. Install:
• Spring "1"
•Pin "2"
• O-ring "3"
• Neutral switch "4"
• Screw (neutral switch) "5"
Apply the lithium soap base grease
on the O-ring.
2. Install:• Hose guide (cylinder head breath-
er hose) "1"
• Bolt (hose guide) "2"
Nut (drive sprocket):
75 Nm (7.5 m•kg, 54
ft•lb)
Bolt (drive chain sprock-
et cover): 7 Nm (0.7 m•kg, 5.1
ft•lb)
Screw (neutral switch):4 Nm (0.4 m•kg, 2.9
ft•lb)
Bolt (hose guide): 10 Nm (1.0 m•kg, 7.2
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: 50–60 mm (2.0–2.4 in)
Nut (wheel axle): 135 Nm (13.5 m•kg, 98
ft•lb)
Locknut: 21 Nm (2.1 m•kg, 15
ft•lb)