2015 YAMAHA YZ250F Fork

STEERING HEAD
4-49
EAS1SM5172
STEERING HEAD
Removing the lower bracket
Order Part name Q’ty Remarks
Use a suitable stand to raise the front wheel
off the ground.
Number plate Refer to “GENERAL CHASSIS” on page 4-1.
Handlebar Refer to “HANDLEBAR” on page 4-31.
1 Front fender 1
2 Steering stem nut 1
3 Front fork leg (s) 2 Refer to “FRONT FORK” on page 4-37.
4 Upper bracket 1
5 Steering ring nut 1
6 Lower bracket 1
7 Bearing race cover 1
8 Upper bearing 1
9 Bearing (lower side) 1
10 Bearing races 2
For installation, reverse the removal proce-
dure.
2
4
5
7
3
1
6
8
9
10
LS
1st
2ndT.R.
LS
LS
T.R.21 Nm (2.1 mlbf) kgf, 15 ft
T.R.9 Nm (0.9 mlbf) kgf, 6.5 ft
T.R.21 Nm (2.1 mlbf) kgf, 15 ft
T.R.10 Nm (1.0 mlbf) kgf, 7.2 ft
T.R.145 Nm (14.5 mlbf) kgf, 105 ft
38 Nm (3.8 m
lbf) kgf, 27 ft
7 Nm (0.7 m
lbf) kgf, 5.1 ft

STEERING HEAD
4-51
2. Install:
• Bearing races
• Upper bearing “1”
• Bearing race cover “2”
TIP
Apply the lithium soap base grease on the
bearing and bearing race cover lip.
3. Install:
• Lower bracket “1”
TIP
Apply the lithium soap base grease on the
bearing, the portion “a” and thread of the steer-
ing stem.
4. Install:
• Steering ring nut “1”
TIP
Install the steering nut with its stepped side “a”
facing downward.
Tighten the steering ring nut with a steering
nut wrench “2”.
Refer to “CHECKING AND ADJUSTING
THE STEERING HEAD” on page 3-33.5. Check the steering stem by turning this lock
to lock. If there is any binding, remove the
steering stem and check the steering bear-
ing.
6. Install:
• Washer “1”
7. Install:
• Front fork “1”
• Upper bracket “2”
TIP
• Temporarily tighten the pinch bolts (lower
bracket).
• Do not tighten the pinch bolts (upper bracket)
yet. Steering ring nut
7 Nm (0.7 m·kgf, 5.1 ft·lbf)
LS
1 a
LSLS
T R..

STEERING HEAD
4-52
8. Install:
• Steering stem nut “1”
TIP
Apply the lithium soap base grease to the con-
tact surface of the steering stem nut when in-
stalling.
9. After tightening the nut, check the steering
for smooth movement. If not, adjust the
steering by loosening the steering ring nut
little by little.
10.Adjust:
• Front fork top end “a”11.Tighten:
• Pinch bolt (upper bracket) “1”
• Pinch bolt (lower bracket) “2”
EWA33DD049
WARNING
Tighten the lower bracket to specified
torque. If torqued too much, it may cause
the front fork to malfunction. Steering stem nut
145 Nm (14.5 m·kgf, 105 ft·lbf)
Front fork top end (standard) “a”
5 mm (0.20 in)T R..
a
Upper bracket pinch bolts
21 Nm (2.1 m·kgf, 15 ft·lbf)
Lower bracket pinch bolts
21 Nm (2.1 m·kgf, 15 ft·lbf)
T R..
T R..
21

AC MAGNETO................................................................................................ 5-58
REMOVING THE AC MAGNETO............................................................. 5-59
CHECKING THE AC MAGNETO ............................................................. 5-59
CHECKING THE WOODRUFF KEY ........................................................ 5-59
INSTALLING THE AC MAGNETO ........................................................... 5-59
CRANKCASE................................................................................................. 5-61
DISASSEMBLING THE CRANKCASE..................................................... 5-64
REMOVING THE CRANKCASE BEARING ............................................. 5-64
CHECKING THE TIMING CHAIN, TIMING CHAIN GUIDE,
OIL STRAINER ........................................................................................ 5-64
CHECKING THE CRANKCASE ............................................................... 5-64
INSTALLING THE OIL SEAL................................................................... 5-65
ASSEMBLING THE CRANKCASE........................................................... 5-65
CRANKSHAFT ASSEMBLY AND BALANCER SHAFT............................... 5-66
REMOVING THE CRANKSHAFT ASSEMBLY ........................................ 5-67
CHECKING THE CRANKSHAFT ASSEMBLY......................................... 5-67
INSTALLING THE CRANKSHAFT ASSEMBLY....................................... 5-68
INSTALLING THE BALANCER SHAFT ................................................... 5-68
TRANSMISSION............................................................................................. 5-69
REMOVING THE TRANSMISSION ......................................................... 5-70
CHECKING THE SHIFT FORKS.............................................................. 5-70
CHECKING THE SHIFT DRUM ASSEMBLY ........................................... 5-71
CHECKING THE TRANSMISSION .......................................................... 5-71
INSTALLING THE TRANSMISSION ........................................................ 5-71

CRANKCASE
5-63
Removing the bearing and oil seal
Order Part name Q’ty Remarks
Transmission Refer to “TRANSMISSION” on page 5-69.
Shift cam and shift fork Refer to “TRANSMISSION” on page 5-69.
1 Circlip 2
2Oil seals 3
3 Bearing 11
For installation, reverse the removal proce-
dure.
LT
LT
LT
2
3
33
3
3
3 3
33
New
1
1
2
3
New
New
LT
22 Nm (2.2 mkgf, 16 ftIbf)T.R.

TRANSMISSION
5-69
EAS1SM5290
TRANSMISSION
Removing the transmission, shift drum assembly, and shift forks
Order Part name Q’ty Remarks
Engine Refer to “ENGINE REMOVAL” on page 5-1.
CrankcaseSeparate.
Refer to “CRANKCASE” on page 5-61.
1 Main axle 1
2 Drive axle 1
3 Long shift fork guide bar 1
4 Short shift fork guide bar 1
5Spring 4
6 Shift cam 1
7 Shift fork 3 (R) 1
8 Shift fork 2 (C) 1
9 Shift fork 1 (L) 1
10 Collars 1
For installation, reverse the removal proce-
dure.
2
10
1
53
4 578
69
M
M
M
M
M
EE
E
E
LS
New

TRANSMISSION
5-70
EAS1SM5291REMOVING THE TRANSMISSION
1. Remove:
• Long shift fork guide bar “1”
• Short shift fork guide bar “2”
• Shift cam “3”
• Shift fork 3 “4”
• Shift fork 2 “5”
• Shift fork 1 “6”
• Main axle “7”
• Drive axle “8”
• Collar “9”
TIP
• Remove assembly with the collar “9” installed
to the crankcase.
• Make a note of the position of each part. Pay
particular attention to the location and direc-
tion of shift forks.
• Remove the main axle and the drive axle all
together by tapping the drive axle lightly with
a soft hammer.
EAS1SM5292
CHECKING THE SHIFT FORKS
1. Check:
• Shift fork cam follower “1”
• Shift fork pawl “2”
Bends/damage/scoring/wear  Replace the
shift fork.
2. Check:
• Shift fork guide bar
Roll the shift fork guide bar on a flat surface.
Bends  Replace.
EWA12840
WARNING
Do not attempt to straighten a bent shift fork
guide bar.
3. Check:
• Shift fork movement
(along the shift fork guide bar)
Rough movement  Replace the shift forks
and shift fork guide bar as a set.
1
4
62
5
3
8
7
9

TRANSMISSION
5-73
6. Install:
• Shift fork 1 (L) “1”
• Shift fork 2 (C) “2”
• Shift fork 3 (R) “3”
• Shift cam “4”
(to the main axle and the drive axle)
TIP
• Apply engine oil to the shift fork grooves.
• Apply engine oil to the shift cam groove and
the bearing contact surface.
• 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 axle.7. Install:
• Long shift fork guide bar “1”
• Short shift fork guide bar “2”
• Spring “3”
TIP
• Screw the spring into the shift fork guide bar
lightly beforehand.
• Apply the engine oil on the shift fork guide
bars.
8. Check:
• Operation of shift cam and shift fork
• Transmission operation
Unsmooth operation  Repair.
3
12
6
24
5
3
7
1
E
E
E
2 13
E