Engine YAMAHA YZ250F 2009 Repair Manual

4-56
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 chain
Cracks/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:
• Bearing
Rotate 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 <Limit>
Runo
ut lim-
it: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)—

4-58
CRANKCASE AND CRANKSHAFT
5. Install:
• Dowel pin "1"
• O-ring "2"
• Right crankcase
To left crankcase.
• Apply the lithium soap base grease
on the O-ring.
• Fit the right crankcase onto the left
crankcase. Tap lightly on the case
with soft hammer.
• When installing the crankcase, the
connecting rod should be posi-
tioned at TDC (top dead center).
6. Tighten:
• Hose guide "1"
• Clutch cable holder "2"
• Bolt (crankcase) "3"
Tighten the crankcase tightening
bolts in stage, using a crisscross pat-
tern.
7. Install:
• Oil delivery pipe 2 "1"
• O-ring "2"
• Bolt (oil delivery pipe 2) "3"
Apply the lithium soap base grease
on the Orings.
8. Install:
• Timing chain "1"
• Timing chain guide (intake side)
"2"
• Bolt (timing chain guide) "3"
9. Remove:
•Sealant
Forced out on the cylinder mating
surface.
10. Apply:
• Engine oil
To the crank pin, bearing and oil
delivery hole.
11. Check:
• Crankshaft and transmission op-
eration.
Unsmooth operation→Repair. Bolt (crankcase):
12 Nm (1.2 m•kg, 8.7
ft•lb)
Bolt (oil delivery pipe 2):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (timing chain guide):
10 Nm (1.0 m•kg, 7.2
ft•lb)

4-59
TRANSMISSION, SHIFT CAM AND SHIFT FORK
TRANSMISSION, SHIFT CAM AND SHIFT FORK
REMOVING THE TRANSMISSION, SHIFT CAM AND SHIFT FORK
Order Part name Q'ty Remarks
Engine Refer to "ENGINE REMOVAL" section.
Separate the crankcase.Refer to "CRANKCASE AND CRANK-
SHAFT" section.
1 Main axle 1 Refer to removal section.
2 Drive axle 1 Refer to removal section.
3 Shift cam 1 Refer to removal section.
4 Shift fork 3 1 Refer to removal section.
5 Shift fork 2 1 Refer to removal section.
6 Shift fork 1 1 Refer to removal section.
7Collar 1

4-61
TRANSMISSION, SHIFT CAM AND SHIFT FORK
• 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. 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.

5-1
FRONT WHEEL AND REAR WHEEL
CHASSIS
This section is intended for those who have basic knowledge and skill concerning the servicing of Yamaha motorcycles
(e.g., Yamaha dealers, service engineers, etc.) Those who have little knowledge and skill concerning servicing are request-
ed not to undertake inspection, adjustment, disassembly, or reassembly only by reference to this manual. It may lead to
servicing trouble and mechanical damage.
FRONT WHEEL AND REAR WHEEL
REMOVING THE FRONT WHEEL
Order 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

5-2
FRONT WHEEL AND REAR WHEEL
REMOVING THE REAR WHEEL
Order 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 3 Refer to removal section.
10 Brake disc 1
5

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

5-7
FRONT BRAKE AND REAR BRAKE
REMOVING THE REAR BRAKE
Order 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

5-16
FRONT FORK
FRONT FORK
REMOVING THE FRONT FORK
Order Part name Q'ty Remarks
Hold the machine by placing the suitable stand
under the engine.Refer to "HANDLING NOTE".
Front wheel Refer to "FRONT WHEEL AND REAR
WHEEL" section.
Front brake caliper Refer to "FRONT BRAKE AND REAR
BRAKE" section.
Number plateRefer to "SEAT, FUEL TANK AND SIDE
COVERS" section in the CHAPTER 4.
1Protector 1
2 Pinch bolt (upper bracket) 2 Only loosening.
3 Damper assembly 1Loosen when disassembling the front fork.
Refer to removal section.
4 Pinch bolt (lower bracket) 2 Only loosening.
5 Front fork 1

5-24
HANDLEBAR
HANDLEBAR
REMOVING THE HANDLEBAR
Order 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