2008 YAMAHA YZ250F clutch

4-31
CLUTCH
REMOVING THE CLUTCH BOSS
1. Remove:•Nut "1"
• Lock washer "2"
• Clutch boss "3"
Straighten the lock washer tab and
use the clutch holding tool "4" to hold
the clutch boss.
A. For USA and CDN
B. Except for USA and CDN
CHECKING THE CLUTCH
HOUSING AND BOSS
1. Inspect: • Clutch housing "1"Cracks/wear/damage
→Replace.
• Clutch boss "2"
Scoring/wear/damage
→Re-
place.
CHECKING THE PRIMARY DRIVEN
GEAR
1. Check: • Circumferential playFree play exists
→Replace.
• Gear teeth "a"
Wear/damage
→Replace. CHECKING THE CLUTCH
SPRINGS
1. Measure:
• Clutch spring free length "a"
Out of specification
→Replace
springs as a set.
CHECKING THE FRICTION
PLATES
1. Measure: • Friction plate thicknessOut of specification
→Replace
friction plate as a set.
Measure at all four points.
CHECKING THE CLUTCH PLATES
1. Measure: • Clutch plate warpageOut of specification
→Replace
clutch plate as a set.
Use a surface plate "1" and thick-
ness gauge "2". CHECKING THE PUSH LEVER
SHAFT
1. Inspect:
• Push lever shaft "1"
Wear/damage
→Replace.
CHECKING THE PUSH ROD
1. Inspect: • Push rod 1 "1"
• Bearing "2"
• Washer "3"
• Push rod 2 "4"
• Ball "5"Wear/damage/bend
→Replace.
INSTALLING THE PUSH LEVER
SHAFT
1. Install: • Push lever shaft "1"
• Bolt (push lever shaft) "2"
• Apply the lithium soap base grease on the oil seal lip.
• Apply the engine oil on the push le-
ver shaft.
• Fit the seat plate "3" in the groove "a" of the push lever shaft and tight-
en the bolt (seat plate).
Clutch holding tool:
YM-91042/90890-04086
Clutch spring free
length:35.7 mm (1.41 in)
: 34.7 mm (1.37
in)
Friction plate thickness: 2.9–3.1 mm (0.114–
0.122 in)
: 2.8 mm (0.110
in)
Warp limit: 0.1 mm (0.004 in)
Bolt (push lever shaft):10 Nm (1.0 m•kg, 7.2
ft•lb)

4-32
CLUTCH
INSTALLING THE CLUTCH
1. Install:• Primary driven gear "1"
• Thrust washer "2"
• Clutch boss "3"
Apply the engine oil on the primary
driven gear inner circumference.
2. Install:• Lock washer "1"
• Nut (clutch boss) "2"
Use the clutch holding tool "3" to hold
the clutch boss.
A. For USA and CDN
B. Except for USA and CDN
3. Bend the lock washer "1" tab. 4. Install:
• Seat plate "1"
• Cushion spring "2"
• Install the seat plate with its cham-fered portion "a" facing the clutch
boss "3".
• Install the seat plate so that it is not caught on the step "b".
• Install the cushion spring with its concave surface "c" facing outward.
5. Install:• Friction plate "1"
• Clutch plate 1 "2"
• Clutch plate 2 "3"
• Install the clutch plates and friction plates alternately on the clutch
boss, starting with a friction plate
and ending with a friction plate.
• Apply the engine oil on the friction plates and clutch plates.
• Unlike the clutch plate 2, the clutch
plate 1 has no surface gloss. Use
the clutch plate 1 for the first while
paying attention to the difference in
surface gloss.
6. Install:• Bearing "1"
•Washer "2"
•Circlip "3" To push rod 1 "4".
Apply the engine oil on the bearing
and washer.
7. Install:• Push rod 2 "1"
• Ball "2"
• Push rod 1 "3"
Apply the engine oil on the push rod
1, 2 and ball.
8. Install:• Pressure plate "1"
9. Install: • Clutch spring "1"
• Bolt (clutch spring) "2"
Tighten the bolts in stage, using a
crisscross pattern.
10. Install:• Dowel pin "1"
• Gasket (clutch cover) "2"
Nut (clutch boss):
60 Nm (6.0 m•kg, 43
ft•lb)
Clutch holding tool: YM-91042/90890-04086
Bolt (clutch spring):
10 Nm (1.0 m•kg, 7.2
ft•lb)

4-33
CLUTCH
11. Install:•Clutch cover "1"
• Bolt (clutch cover)
Tighten the bolts in stage, using a
crisscross pattern.
Bolt (clutch cover): 10 Nm (1.0 m•kg, 7.2
ft•lb)

4-38
BALANCER
BALANCER
REMOVING THE BALANCEROrder Part name Q'ty Remarks Primary driven gear Refer to "CLUTCH" section.
Right crankcase cover Refer to "OIL FILTER ELEMENT AND WA-
TER PUMP" section.
Stator Refer to "CDI MAGNETO" section.
1 Nut (primary drive gear) 1 Refer to removal section.
2 Nut (balancer shaft driven gear) 1 Refer to removal section.
3 Lock washer 1
4 Primary drive gear 1
5 Balancer shaft drive gear 1
6 Lock washer 1
7 Balancer shaft driven gear 1
8 Balancer shaft 1 Refer to removal section.

4-40
OIL PUMP
OIL PUMP
REMOVING THE OIL PUMPOrder Part name Q'ty Remarks Primary driven gear Refer to "CLUTCH" section.
Right crankcase cover Refer to "OIL FILTER ELEMENT AND WA-
TER PUMP" section.
1 Circlip 1
2 Washer 1
3 Oil pump drive gear 1
4 Oil pump assembly 1
5 Outer rotor 2 1
6 Circlip 1
7 Inner rotor 2 1
8 Dowel pin 1
9 Oil pump cover 1
10 Outer rotor 1 1
11 Inner rotor 1 1
12 Dowel pin 1
13 Washer 1
14 Oil pump drive shaft 1

4-51
ENGINE REMOVAL
ENGINE REMOVAL
REMOVING THE ENGINEOrder Part name Q'ty Remarks Hold the machine by placing the suitable stand
under the frame. Refer to "HANDLING NOTE".
Seat and fuel tank Refer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
Carburetor Refer to "CARBURETOR" section.
Exhaust pipe and silencer Refer to "EXHAUST PIPE AND SILENCER"
section.
Clutch cable Disconnect at the engine side.
Radiator Refer to "RADIATOR" section.
Shift pedal Refer to "KICK SHAFT AND SHIFT SHAFT"
section.
Cylinder head breather hose Refer to "CAMSHAFTS" section.
Drain the engine oil. Refer to "CHANGING THE ENGINE OIL"
section in the CHAPTER 3.
Oil hose and oil tank breather hose Refer to "OIL PUMP" section.
Ignition coil
Disconnect the CDI magneto lead.
Right engine guard

4-55
CRANKCASE AND CRANKSHAFT
CRANKCASE AND CRANKSHAFT
REMOVING THE CRANKSHAFTOrder Part name Q'ty Remarks Engine Refer to "ENGINE REMOVAL" section.
Piston Refer to "CYLINDER AND PISTON" section.
Kick shaft assembly Refer to "KICK SHAFT AND SHIFT SHAFT"
section.
Segment Refer to "KICK SHAFT AND SHIFT SHAFT"
section.
Stator Refer to "CDI MAGNETO" section.
Balancer shaft Refer to "BALANCER" section.
1 Timing chain guide (intake side) 1
2 Timing chain 1
3 Oil delivery pipe 2 1
4 Bolt [L = 45 mm (1.77 in)] 6 Refer to removal section.
5 Bolt [L = 55 mm (2.17 in)] 1 Refer to removal section.
6 Bolt [L = 70 mm (2.76 in)] 4 Refer to removal section.
7 Hose guide 1 Refer to removal section.
8 Clutch cable holder 1 Refer to removal section.
9 Right crankcase 1 Refer to removal section.

4-58
CRANKCASE AND CRANKSHAFT
DISASSEMBLING THE
CRANKCASE
1. Separate:• Right crankcase
• Left crankcase
Separation steps:
a. Remove the crankcase bolts "1", hose guide "2" and clutch cable
holder "3".
Loosen each bolt 1/4 of a turn at a
time and after all the bolts are loos-
ened, remove them.
b. Remove the right crankcase "4".
• Place the crankcase with its left half
downward and split the right half
apart while lifting it horizontally by
lightly tapping the projection "a" on
it using a soft hammer.
• When splitting it, leave the crank-
shaft and transmission with the left
half.
Use soft hammer to tap on the
case half. Tap only on reinforced
portions of case. Do not tap on
gasket mating surface. Work slow-
ly and carefully. Make sure the
case halves separate evenly. If the
cases do not separate, check for a
remaining case bolt or fitting. Do
not force.
c. Remove the dowel pins and O- ring.
REMOVING THE CRANKSHAFT
1. Remove:• Crankshaft "1"Use the crankcase separating
tool "2".
Do not use a hammer to drive out
the crankshaft.
REMOVING THE CRANKCASE
BEARING
1. Remove:• Bearing "1"
• Remove the bearing from the
crankcase by pressing its inner
race.
• Do not use the removed bearing.
CHECKING THE TIMING CHAIN
AND TIMING CHAIN GUIDE
1. Inspect:
•Timing chainCracks/stiff
→Replace the timing
chain and camshaft sprocket as a
set.
2. Inspect: • Timing chain guide
Wear/damage
→Replace.
CHECKING THE CRANKCASE
1. Inspect: • Contacting surface "a"Scratches
→Replace.
• Engine mounting boss "b", crank- case
Cracks/damage
→Replace. 2. Inspect:
• BearingRotate inner race with a finger.
Rough spot/seizure
→Replace.
3. Inspect: •Oil seal
Damage
→Replace.
CHECKING THE CRANKSHAFT
1. Measure: • Runout limit "a"
• Small end free play limit "b"
• Connecting rod big end side clearance "c"
• Crank width "d" Out of specification
→Replace.
Use the dial gauge and a thick-
ness gauge.
Crankcase separating
tool: YU-1135-A/90890-
01135
Dial gauge and stand:YU-3097/90890-01252
Standard it>
Runou
t limit: 0.03 mm (0.0012
in) 0.05
mm
(0.002
in)
Small
end
free
play: 0.4–1.0 mm
(0.016–0.039 in) 2.0 mm
(0.08 in)
Side
clear-
ance: 0.15–0.45 mm
(0.0059–0.0177 in) 0.50
mm
(0.02 in)
Crack
width: 55.95–56.00
mm (2.203– 2.205 in) —