YAMAHA YZ250F 2012 Owners Manual

4-57
CRANKCASE AND CRANKSHAFT
CRANKCASE AND CRANKSHAFT
REMOVING THE CRANKSHAFT
Order Part name Q'ty Remarks
Engine Refer to "ENGINE REMOVAL" section.
Piston Refer to "CYLINDER AND PISTON" section.
Kick shaft assemblyRefer to "KICK SHAFT AND SHIFT SHAFT"
section.
SegmentRefer 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
10 Left crankcase 1 Refer to removal section.
11 Oil strainer 1
12 Crankshaft 1 Refer to removal section. Order Part name Q'ty Remarks

4-59
CRANKCASE AND CRANKSHAFT
REMOVING THE CRANKCASE BEARING
Order Part name Q'ty Remarks
TransmissionRefer to "TRANSMISSION, SHIFT CAM AND
SHIFT FORK" section.
Shift cam and shift fork Refer to "TRANSMISSION, SHIFT CAM AND
SHIFT FORK" section.
1 Oil seal 2
2 Bearing 10 Refer to removal section.

4-60
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
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)—

4-61
CRANKCASE AND CRANKSHAFT
CHECKING THE OIL STRAINER
1. Inspect:
• Oil strainer
Damage→Replace.
CHECKING THE OIL DELIVERY
PIPE 2
1. Inspect:
• Oil delivery pipe 2 "1"
• O-ring "2"
Damage→Replace.
• Oil orifice "a"
Clogged→Blow.
INSTALLING THE CRANKCASE
BEARING
1. Install:
• Bearing
• Bearing stopper
• Bolt (bearing stopper)
• Screw (bearing stopper) • Screw [bearing stopper (crank-
shaft)] "1"
To left and right crankcase.
• Install the bearing by pressing its
outer race parallel.
• To prevent the screw [bearing stop-
per (crankshaft)] from becoming
loose, crush the screw head periph-
ery "a" into the concave "b" using a
punch etc. In so doing, take care
not to damage the screwdriver re-
ceiving hole in the screw head.
INSTALLING THE CRANKSHAFT
1. Install:
• Crankshaft "1"
Use the crankshaft installing tool
"2", "3", "4" and "5".
• Hold the connecting rod at top dead
center with one hand while turning
the nut of the installing tool with the
other. Operate the installing tool un-
til the crankshaft bottoms against
the bearing.
• Before installing the crankshaft,
clean the contacting surface of
crankcase.
• Apply the molybdenum disulfide
grease to the crankshaft to pre-
vent it from being scratched.
• Do not use a hammer to drive in
the crankshaft.
A. For USA and CDN
B. Except for USA and CDN
2. Check:
• Shifter operation
• Transmission operation
Unsmooth operation→Repair.
3. Install:
• Oil strainer "1"
• Bolt (oil strainer) "2"
4. Apply:
• Sealant
On the right crankcase "1".
Clean the contacting surface of left
and right crankcase before applying Bolt (bearing stopper):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Screw (bearing stopper):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Screw [bearing stopper
(crankshaft)]:
14 Nm (1.4 m•kg, 10
ft•lb)
Crankshaft installing pot
"2":
YU-90050/90890-01274
Crankshaft installing bolt
"3":
YU-90050/90890-01275
Adapter (M12) "4":
YU-90063/90890-01278
Spacer (crankshaft in-
staller) "5":
YU-91044/90890-04081
Bolt (oil strainer):
10 Nm (1.0 m•kg, 7.2
ft•lb)
YAMAHA Bond No.1215
(ThreeBond
® No.1215):
90890-85505

4-62
CRANKCASE AND CRANKSHAFT
the sealant.
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)

4-63
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.
7 Collar 1

4-64
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 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 (18T) "2"
•Collar "3"
• 4th pinion gear (18T) "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 (22T) "2"
• 3rd wheel gear (26T) "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.

4-65
TRANSMISSION, SHIFT CAM AND SHIFT FORK
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. 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 engine 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
5 Collar 2
6 Oil seal 2
7 Bearing 2 Refer to removal section.
8 Brake disc 1