2014 YAMAHA YZ250F Owners Manual

SWINGARM
4-61
EAS1SM1185REMOVING THE SWINGARM
1. Use a suitable stand to raise the rear wheel
off the ground.
EWA13120
WARNING
Securely support the vehicle so that there is
no danger of it falling over.
2. Measure:
• Swingarm side play
• Swingarm vertical movement
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a. Measure the tightening torque of the pivot
shaft nut.
b. Measure the swingarm side play “a” by mov-
ing the swingarm from side to side.
c. If the swingarm side play is out of specifica-
tion, check the spacers, the bearings, and
the collars.
d. Check the swingarm vertical movement “b”
by moving the swingarm up and down.
If swingarm vertical movement is not smooth
or if there is binding, check the spacers, the
bearings, and the collars.
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EAS1SM1186REMOVING THE BEARING
1. Remove:
• Bearing “1”
TIP
Remove the bearing by pressing its outer race.
EAS1SM1187CHECKING THE SWINGARM
1. Check:
• Swingarm
Bends/cracks/damage  Replace.
2. Check:
• Pivot shaft
Roll the pivot shaft on a flat surface.
Bends  Replace.
EWA13770
WARNING
Do not attempt to straighten a bent pivot
shaft.
3. Wash with kerosene:
• Pivot shaft
• Spacers
•Collars
• Bearing
4. Check:
• Oil seals
Damage  Replace.
• Bearing
• Spacers
Free play exists/unsmooth revolution/rust 
Replace bearing and bushing as a set.
EAS1SM1188
Pivot shaft nut
85 Nm (8.5 m·kgf, 61 ft·lbf)
Swingarm end free play limit (ra-
dial)
1.0 mm (0.04 in)
T R..

SWINGARM
4-62
INSTALLING THE SWINGARM
1. Lubricate:
• Bearing
•Collars
• Spacers
• Oil seal
• Pivot shaft
2. Install:
• Bearing “1”
• Oil seals “2”
(to the swingarm)
TIP
First install the outer and then the inner bear-
ings to a specified depth from inside.
3. Install:
• Swingarm
TIP
Install the pivot shaft from the right.
4. Install:
• Rear wheel
Refer to “REAR WHEEL” on page 4-7.
5. Adjust:
• Drive chain slack
Refer to “ADJUSTING THE DRIVE CHAIN
SLACK” on page 3-27.Recommended lubricant
Molybdenum disulfide grease
Installed depth “a”
0–0.5 mm (0–0.02 in)
Installed depth “b”
6.5 mm (0.26 in)
Pivot shaft nut
85 Nm (8.5 m·kgf, 61 ft·lbf)
Drive chain slack
50–60 mm (1.97–2.36 in)
New
New
2 22
1 1
aaa
b ba
NewNewNew
T R..

CHAIN DRIVE
4-63
EAS1SM1189
CHAIN DRIVE
Removing the drive chain
Job Order Part name Q’ty Servicing Information
Drive sprocket Refer to “ENGINE REMOVAL” on page 5-1.
1 Drive chain 1
For installation, reverse the removal proce-
dure.
1
T.R.75 Nm (7.5 mlbf) kgf, 54 ft
T.R.7 Nm (0.7 mlbf) kgf, 5.1 ft

CHAIN DRIVE
4-64
EAS1SM1190REMOVING THE DRIVE CHAIN
1. Use a suitable stand to raise the rear wheel
off the ground.
EWA13120
WARNING
Securely support the vehicle so that there is
no danger of it falling over.
2. Remove:
• Joint clip
• Drive chain joint “1”
• Drive chain “2”
EAS1SM1191CHECKING THE DRIVE CHAIN
1. Measure:
• 15-link section “a” of the drive chain
Out of specification  Replace the drive
chain.
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a. Measure the length “a” between the inner
sides of the pins and the length “b” between
the outer sides of the pins on a 15-link sec-
tion of the drive chain as shown in the illus-
tration.
b. Calculate the length “c” of the 15-link section
of the drive chain using the following formu-
la.
Drive chain 15-link section length “c” =
(length “a” between pin inner sides + length
“b” between pin outer sides)/2
TIP
• When measuring a 15-link section of the drive
chain, make sure that the drive chain is taut.
• Perform this procedure 2–3 times, at a differ-
ent location each time.
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2. Check:
•Drive chain
Stiffness  Clean, lubricate, or replace.
3. Clean:
•Drive chain
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a. Wipe the drive chain with a clean cloth.
b. Put the drive chain in kerosene and remove
any remaining dirt.
c. Remove the drive chain from the kerosene
and completely dry it.
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15-link length limit
242.9 mm (9.56 in)

CHAIN DRIVE
4-65
4. Check:
• Drive chain rollers “1”
Damage/wear  Replace the drive chain.
• Drive chain side plates “2”
Damage/wear  Replace the drive chain.
5. Lubricate:
•Drive chain
EAS1SM1192CHECKING THE DRIVE SPROCKET
1. Check:
• Drive sprocket
More than 1/4 tooth wear “a”  Replace the
drive sprocket and the rear wheel sprocket
as a set.
Bent tooth  Replace the drive sprocket
and the rear wheel sprocket as a set.
EAS1SM1193CHECKING THE REAR WHEEL SPROCKET
Refer to “CHECKING AND REPLACING THE
REAR WHEEL SPROCKET” on page 4-8.
EAS1SM1194INSTALLING THE DRIVE CHAIN
1. Install:
• Drive chain “1”
• Drive chain joint “2”
• Joint clip “3”
EWA
WARNING
When installing the joint clip, always keep
the direction as shown in the figure.2. Lubricate:
•Drive chain
3. Install:
• Drive sprocket
• Lock washer
• Drive sprocket nut
Refer to “ENGINE REMOVAL” on page 5-1.
ECA1DX1014
NOTICE
Never install a new drive chain onto worn
drive sprockets; this will dramatically short-
en the drive chain’s life.
4. Adjust:
• Drive chain slack
Refer to “ADJUSTING THE DRIVE CHAIN
SLACK” on page 3-27.
ECA13550
NOTICE
A drive chain that is too tight will overload
the engine and other vital parts, and one
that is too loose can skip and damage the
swingarm or cause an accident. Therefore,
keep the drive chain slack within the speci-
fied limits.
b. Correct
1. Drive chain roller
2. Drive sprocket
New
Drive sprocket nut
75 Nm (7.5 m·kgf, 54 ft·lbf)
Drive chain slack
50–60 mm (1.97–2.36 in)
New
T R..

CHAIN DRIVE
4-66

5
ENGINE
ENGINE REMOVAL......................................................................................... 5-1
REMOVING THE SILENCER ..................................................................... 5-6
REMOVING THE EXHAUST PIPE 2.......................................................... 5-6
REMOVING THE DRIVE SPROCKET ....................................................... 5-6
REMOVING THE ENGINE ......................................................................... 5-7
CHECKING THE SILENCER AND EXHAUST PIPE.................................. 5-7
CHANGING THE SILENCER FIBER ......................................................... 5-7
INSTALLING THE ENGINE........................................................................ 5-8
INSTALLING THE BRAKE PEDAL ............................................................ 5-9
INSTALLING THE DRIVE SPROCKET...................................................... 5-9
INSTALLING THE EXHAUST PIPE AND MUFFLER............................... 5-10
CAMSHAFT.................................................................................................... 5-11
REMOVING THE CAMSHAFT ................................................................. 5-13
CHECKING THE CAMSHAFT.................................................................. 5-14
CHECKING THE TIMING CHAIN AND CAMSHAFT SPROCKET .......... 5-15
CHECKING THE TIMING CHAIN TENSIONERS .................................... 5-15
CHECKING THE DECOMPRESSION SYSTEM...................................... 5-16
INSTALLING THE CAMSHAFTS ............................................................. 5-16
CYLINDER HEAD........................................................................................... 5-18
REMOVING THE CYLINDER HEAD........................................................ 5-20
CHECKING THE TIMING CHAIN GUIDE (INTAKE SIDE) ...................... 5-20
CHECKING THE CYLINDER HEAD ........................................................ 5-20
INSTALLING THE CYLINDER HEAD ...................................................... 5-21
VALVES AND VALVE SPRINGS................................................................... 5-22
REMOVING THE VALVES ....................................................................... 5-23
CHECKING THE VALVES AND VALVE GUIDES ................................... 5-24
CHECKING THE VALVE SEATS ............................................................. 5-25
CHECKING THE VALVE SPRINGS......................................................... 5-27
CHECKING THE VALVE LIFTERS .......................................................... 5-27
INSTALLING THE VALVES ..................................................................... 5-28
CYLINDER AND PISTON............................................................................... 5-30
REMOVING THE PISTON ....................................................................... 5-31
CHECKING THE CYLINDER AND PISTON ............................................ 5-31
CHECKING THE PISTON RINGS............................................................ 5-32
CHECKING THE PISTON PIN ................................................................. 5-33
INSTALLING THE PISTON AND CYLINDER .......................................... 5-33

CLUTCH......................................................................................................... 5-35
REMOVING THE CLUTCH ...................................................................... 5-38
CHECKING THE FRICTION PLATES...................................................... 5-38
CHECKING THE CLUTCH PLATES ........................................................ 5-38
CHECKING THE CLUTCH SPRINGS...................................................... 5-38
CHECKING THE CLUTCH HOUSING ..................................................... 5-39
CHECKING THE CLUTCH BOSS ............................................................ 5-39
CHECKING THE PRESSURE PLATE ..................................................... 5-39
CHECKING THE PUSH LEVER SHAFT .................................................. 5-39
CHECKING THE CLUTCH PUSH RODS ................................................ 5-39
CHECKING THE PRIMARY DRIVE GEAR .............................................. 5-39
CHECKING THE PRIMARY DRIVEN GEAR ........................................... 5-40
INSTALLING THE OIL SEAL................................................................... 5-40
INSTALLING THE RIGHT CRANKCASE COVER ................................... 5-40
INSTALLING THE CLUTCH ..................................................................... 5-41
INSTALLING THE KICKSTARTER LEVER ............................................. 5-43
KICKSTATER................................................................................................. 5-44
REMOVING THE KICK SHAFT ASSEMBLY ........................................... 5-45
CHECKING THE KICK SHAFT AND RATCHET WHEEL ........................ 5-45
CHECKING THE KICK GEAR, KICK IDLE GEAR,
AND RATCHET WHEEL ......................................................................... 5-47
INSTALLING THE KICK SHAFT ASSEMBLY .......................................... 5-45
INSTALLING THE KICK IDLE GEAR ....................................................... 5-46
SHIFT SHAFT................................................................................................. 5-47
REMOVING THE SHIFT GUIDE AND SHIFT LEVER ASSEMBLY ......... 5-49
REMOVING THE SEGMENT ................................................................... 5-49
CHECKING THE SHIFT SHAFT .............................................................. 5-49
CHECKING THE SHIFT GUIDE AND SHIFT LEVER ASSEMBLY ......... 5-49
CHECKING THE STOPPER LEVER ....................................................... 5-49
INSTALLING THE STOPPER LEVER ..................................................... 5-50
INSTALLING THE SEGMENT.................................................................. 5-50
INSTALLING THE SHIFT GUIDE AND SHIFT LEVER ASSEMBLY ....... 5-50
INSTALLING THE SHIFT SHAFT ............................................................ 5-51
INSTALLING THE SHIFT PEDAL ............................................................ 5-51
OIL PUMP AND BALANCER GEAR............................................................. 5-52
REMOVING THE BALANCER ................................................................. 5-54
CHECKING THE PRIMARY DRIVE GEAR, BALANCER SHAFT
DRIVE GEAR, AND BALANCER WEIGHT GEAR .................................. 5-56
CHECKING THE BALANCER .................................................................. 5-54
CHECKING THE OIL PUMP .................................................................... 5-54
ASSEMBLING THE OIL PUMP ................................................................ 5-55
INSTALLING THE OIL PUMP AND BALANCER GEAR .......................... 5-55