engine YAMAHA YZ250F 2010 Owner's Guide

3-12
ENGINE
c. Select the proper pad using the pad selecting table.
The thickness "a" of each pad is indi-
cated in hundredths of millimeters on
the pad upper surface.
d. Round off the last digit of the in-stalled pad number to the nearest
increment.
EXAMPLE:
Installed pad number = 148
Rounded off value = 150
Pads can only be selected in 0.05
mm increments.
e. Locate the rounded-off value and the measured valve clearance in
the chart "PAD SELECTION TA-
BLE". The field where these two
coordinates intersect shows the
new pad number to use.
Use the new pad number only as a
guide when verifying the valve clear-
ance adjustment.
f. Install the new pads "3" and the
valve lifters "4".
• Apply the engine oil on the valve lift-ers.
• Apply the molybdenum disulfide oil
on the valve stem ends.
• Valve lifter must turn smoothly
when rotated with a finger.
• Be careful to reinstall valve lifters and pads in their original place.
g. Install the camshafts (exhaust
and intake).
Refer to "CAMSHAFTS" section
in the CHAPTER 4.
Pad range Pad Availabili-
ty: 25 incre-
ments
No.
120–N o. 240 1.20
mm–2.
40 mm Pads are avail-
able in 0.05 mm increments
Last digit of pad number Rounded valve
0, 1 or 2 0
4, 5 or 6 5 8 or 9 10

3-13
ENGINE
INTAKE
EXHAUST
120 125 130 135 140 145 150 155 160 165 170175 180 185 190 195 200 205 210 215 220 225 230 235 240
0.00 - 0.01
0.02 - 0.06
0.07 - 0.11
0.12 - 0.17
0.18 - 0.22
0.23 - 0.27
0.28 - 0.32
0.33 - 0.37
0.38 - 0.42
0.43 - 0.47
0.48 - 0.52
0.53 - 0.57
0.58 - 0.62
0.63 - 0.67
0.68 - 0.72
0.73 - 0.77
0.78 - 0.82
0.83 - 0.87
0.88 - 0.92
0.93 - 0.97
0.98 - 1.02
1.03 - 1.07
1.08 - 1.12
1.13 - 1.17
1.18 - 1.22
1.23 - 1.27
1.28 - 1.32
120 125 130 135 140 145 150 155160 165 170 175 180 185 190 195 200 205 210 215 220 225 230120 125 130 135 140 145
150 155 160 165
170 175 180 185 190 195 200 205 210 215 220 225 230 235
125130135140145150155160165170175180 185 190 195 200 205 210 215 220 225 230 235240
130135140145150155160165170175180185 190 195 200 205 210 215 220 225 230 235240
135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
165 170 175 180 185 190 195 200 205 210 215 220 225 230 235240
170 175 180 185 190 195 200 205 210 215 220 225 230 235240
175 180 185 190 195 200 205 210 215 220 225 230 235240
180 185 190 195 200 205 210 215 220 225 230 235 240
185 190 195 200 205 210 215 220 225 230 235
240
190 195 200 205 210 215 220 225 230 235240
195 200 205 210 215 220 225 230 235240
200 205 210 215 220 225 230 235240
205 210 215 220 225 230 235240
210 215 220 225 230 235240
215 220 225 230 235240
220 225 230 235240
225 230 235240
230 235240
235240
240
150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225
120 125 130 135 140 145
1.33 - 1.37
VALVE CLEARANCE (cold): 0.12 - 0.17 mm
Example: Installed is 175 Measured clearance is 0.23 mm
Replace 175 pad with 185 pad
MEASURED
CLEARANCE INSTALLED PAD NUMBER
STANDARD CLEARANCE
Pad number: (example)
Pad No. 175 = 1.75 mm
Pad No. 185 = 1.85 mm
MEASURED
CLEARANCE INSTALLED PAD NUMBER
120 125 130 135 140 145 150 155 160 165 170
175 180 185 190 195 200 205 210 215 220 225 230 235 240
0.00 - 0.04 120 125 130 135 140 145 150 155
160 165 170 175 180 185 190 195 200 205 210 215 220 225
0.05 - 0.09
120 125 130 135 140 145 150 155 160165 170 175 180 185 190 195 200 205 210 215 220 225 230
0.10 - 0.16
120125130135140145150155160165170 175 180 185 190 195 200 205 210 215 220 225230235
0.17 - 0.22STANDARD CLEARANCE
0.23 - 0.25 125 130 135 140 145 150 155 160 165 170 175
180 185 190 195 200 205 210 215 220 225230235240
0.26 - 0.30130135140145150155160165170175180185 190 195 200 205 210 215 220 225230235240
0.31 - 0.35 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.36 - 0.40 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.41 - 0.45 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.46 - 0.50 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.51 - 0.55 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.56 - 0.60 160 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.61 - 0.65 165 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.66 - 0.70 170 175 180 185 190 195 200 205 210 215 220 225230235240
0.71 - 0.75 175 180 185 190 195 200 205 210 215 220 225230235240
0.76 - 0.80 180 185 190 195 200 205 210 215 220 225230235240
0.81 - 0.85 185 190 195 200 205 210 215 220 225230235240
VALVE CLEARANCE (cold): 0.17 - 0.22 mm
Example: Installed is 175 Measured clearance is 0.27 mm
Replace 175 pad with 185 pad Pad number: (example)
Pad No. 175 = 1.75 mm
Pad No. 185 = 1.85 mm0.86 - 0.90 190 195 200 205 210 215 220 225230235240
0.91 - 0.95 195 200 205 210 215 220 225230235240
0.96 - 1.00 200 205 210 215 220 225230235240
1.01 - 1.05 205 210 215 220 225230235240
1.06 - 1.10 210 215 220 225230235240
1.11 - 1.15 215 220 225230235240
1.16 - 1.20 220 225230235240
1.21 - 1.25 225230235240
1.26 - 1.30 230235240
1.31 - 1.35 235240
1.36 - 1.40 240

3-17
CHASSIS
CHECKING THE SPROCKET
1. Inspect:• Sprocket teeth "a"Excessive wear →Replace.
Replace the drive sprocket, rear
wheel sprocket and drive chain as a
set.
CHECKING THE DRIVE CHAIN
1. Measure:
• Drive chain length (15 links) "a"Out of specification →Replace.
• While measuring the drive chain
length, push down on the drive
chain to increase its tension.
• Measure the length between drive
chain roller "1" and "16" as shown.
• Perform this measurement at two or three different places.
2. Remove:• Master link clip
•Joint "1"
• Drive chain "2" 3. Clean:
• Drive chainPlace it in kerosene, and brush off
as much dirt as possible. Then re-
move the drive chain from the ker-
osene and dry the drive chain.
4. Check: • Drive chain stiffness "a"
Clean and oil the drive chain and
hold as illustrated.
Stiff →Replace the drive chain.
5. Install: • Drive chain "1"
•Joint "2"
• Master link clip "3"
Be sure to install the master link
clip to the direction as shown.
a. Turning direction
6. Lubricate: • Drive chain ADJUSTING THE DRIVE CHAIN
SLACK
1. Elevate the rear wheel by placing
the suitable stand under the en-
gine.
2. Check: • Drive chain slack "a"
Above the seal guard installation
bolt.
Out of specification →Adjust.
Before checking and/or adjusting, ro-
tate the rear wheel through several
revolutions and check the slack sev-
eral times to find the tightest point.
Check and/or adjust the drive chain
slack with the rear wheel in this "tight
chain" position.
3. Adjust:
• Drive chain slack
Drive chain slack adjustment
steps:
a. Loosen the axle nut "1" and lock- nuts "2".
b. Adjust the drive chain slack by turning the adjusters "3".
c. Turn each adjuster exactly the same amount to maintain correct
axle alignment. (There are marks
"a" on each side of the drive chain
puller alignment.) NOTICE: Im-
proper drive chain slack will
overload the engine aswell as
other vital parts of the motorcy-
cle and can lead to chain slip-
page or breakage. To prevent
this from occurring, keep the
drive chain slack within the
specified limits.
Drive chain length (15
links):
: 242.9 mm
(9.563 in)
Drive chain lubricant:
SAE 10W-40 motor oil
or suitable chain lubri-
cants
Drive chain slack: 50–60 mm (2.0–2.4 in)
To tighten →Turn the adjuster "3"
counterclockwise.
To loosen →Turn the adjuster "3"
clockwise and push wheel for-
ward.

3-18
CHASSIS
A. Right
B. Left
Turn the adjuster so that the drive
chain is in line with the sprocket, as
viewed from the rear.
d. Tighten the axle nut while pushing down the drive chain.
e. Tighten the locknuts.
CHECKING THE FRONT FORK
1. Inspect: • Front fork smooth action
Operate the front brake and
stroke the front fork.
Unsmooth action/oil leakage →
Repair or replace.
CHECKING THE FRONT FORK
PROTECTOR GUIDE
1. Inspect: • Protector guide "1"Out of specification →Replacet.
The protector guide reaches the limit
of its use when it is worn down to the
same height "a" as of the outer tube
circumference.
CLEANING THE FRONT FORK OIL
SEAL AND DUST SEAL
1. Remove:
•Protector
• Dust seal "1"
Use a thin screw driver, and be care-
ful not to damage the inner fork tube
and dust seal.
2. Clean:• Dust seal "a"
• Oil seal "b"
• Clean the dust seal and oil seal af-
ter every run.
• Apply the lithium soap base grease on the inner tube.
RELIEVING THE FRONT FORK
INTERNAL PRESSURE
If the front fork initial movement feels
stiff during a run, re lieve the front fork
internal pressure.
1. Elevate the front wheel by placing a suitable stand under the engine.
2. Remove the air bleed screw "1" and release the internal pressure
from the front fork.
3. Install: • Air bleed screw ADJUSTING THE FRONT FORK
REBOUND DAMPING FORCE
1. Adjust:
• Rebound damping forceBy turning the adjuster "1".
• STANDARD POSITION: This is the position which is back
by the specific number of clicks
from the fully turned-in position.
Do not force the adjuster past the
minimum or maximum extent of
adjustment. The adjuster may be
damaged.
Always adjust each front fork to
the same setting. Uneven adjust-
ment can cause poor handling and
loss of stability.
Axle nut: 135 Nm (13.5 m•kg, 98
ft•lb)
Locknut: 21 Nm (2.1 m•kg, 15
ft•lb)
Air bleed screw:
1 Nm (0.1 m•kg, 0.7
ft•lb)
Stiffer "a" →Increase the re-
bound damping force. (Turn
the adjuster "1" in.)
Softer "b" →Decrease the re-
bound damping force. (Turn
the adjuster "1" out.)
Extent of adjustment:
Maximum Minimum
Fully turned in
position 20 clicks out
(from maximum
position)
Standard position: 10 clicks out
* 9 clicks out
* Except for USA and CDN

3-21
CHASSIS
CHECKING AND TIGHTENING THE
SPOKES
The following procedure applies to all
of the spokes.
1. Check:• SpokesBend/damage →Replace.
Loose spoke →Retighten.
Tap the spokes with a screw-
driver.
A tight spoke will emit a clear, ringing
tone; a loose spoke will sound flat.
2. Tighten: • Spokes
(with a spoke nipple wrench "1")
Be sure to retighten these spokes be-
fore and after break-in.
CHECKING THE WHEELS
1. Inspect:• Wheel runout
Elevate the wheel and turn it.
Abnormal runout → Replace. 2. Inspect:
• Bearing free playExist play →Replace.
CHECKING AND ADJUSTING THE
STEERING HEAD
1. Place a stand under the engine to raise the front wheel off the
ground. WARNING! Securely
support the vehicle so that
there is no danger of it falling
over.
2. Check: • Steering stemGrasp the bottom of the forks and
gently rock the fork assembly
back and forth.
Free play →Adjust steering head.
3. Check: • Steering smooth actionTurn the handlebar lock to lock.
Unsmooth action →Adjust steer-
ing ring nut.
4. Adjust: • Steering ring nut
Steering ring nut adjustment
steps:
a. Remove the number plate.
b. Remove the handlebar and upper
bracket. c. Loosen the steering ring nut "1"
using the steering nut wrench "2".
d. Tighten the steering ring nut "3" using steering nut wrench "4".
• Apply the lithium soap base grease on the thread of the steering stem.
• Set the torque wrench to the steer-
ing nut wrench so that they form a
right angle.
e. Loosen the steering ring nut one turn.
f. Retighten the steering ring nut us- ing the steering nut wrench.
Avoid over-tightening.
g. Check the steering stem by turn-ing it lock to lock. If there is any
binding, remove the steering stem
assembly and inspect the steer-
ing bearings.
Spoke nipple wrench:
YM-01521/90980-01521
Spokes: 3 Nm (0.3 m•kg, 2.2
ft•lb)
Steering nut wrench:YU-33975/90890-01403
Steering nut wrench: YU-33975/90890-01403
Steering ring nut (initial
tightening): 38 Nm (3.8 m•kg, 27
ft•lb)
Steering ring nut (final
tightening): 7 Nm (0.7 m•kg, 5.1
ft•lb)

3-24
ELECTRICAL
ELECTRICAL
CHECKING THE SPARK PLUG
1. Remove:• Spark plug
2. Inspect:
• Electrode "1"Wear/damage →Replace.
• Insulator color "2"
Normal condition is a medium to
light tan color.
Distinctly different color →Check
the engine condition.
When the engine runs for many hours
at low speeds, the spark plug insula-
tor will become sooty, even if the en-
gine and carburetor are in good
operating condition.
3. Measure: • Plug gap "a"Use a wire gauge or thickness
gauge.
Out of specification →Regap.
4. Clean the plug with a spark plug cleaner if necessary.
5. Tighten: • Spark plug
• Before installing a spark plug, clean the gasket surface and plug sur-
face.
• Finger-tighten "a" the spark plug before torquing to specification "b".
CHECKING THE IGNITION TIMING
1. Remove:• Timing mark accessing screw "1"
2. Attach: • Timing light
• Digital tachometerTo the ignition coil lead (orange
lead"1").
3. Adjust: • Engine idling speedRefer to "ADJUSTING THE EN-
GINE IDLING SPEED" section.
4. Check: • Ignition timingVisually check the stationary
pointer "a" is within the firing
range "b" on the rotor.
Incorrect firing range →Check ro-
tor and pickup assembly.
5. Install: • Timing mark accessing screw
Spark plug gap:
0.7–0.8 mm
(0.028–0.031 in)
Spark plug: 13 Nm (1.3 m•kg, 9.4
ft•lb)
Timing light:
YM-33277-A/90890-
03141

4-1
SEAT, FUEL TANK AND SIDE COVERS
ENGINE
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.
SEAT, FUEL TANK AND SIDE COVERS
REMOVING THE SEAT, FUEL TANK AND SIDE COVERS
Order Part name Q'ty Remarks Turn the fuel cock to "OFF".
Disconnect the fuel hose.
1Seat 1
2 Air scoop (left and right) 2
3 Bolt (fuel tank) 1
4 Fitting band 1
5 Fuel tank 1
6 Left side cover 1 Refer to removal section.
7 Right side cover 1 Refer to removal section.
8 Number plate 1 Refer to removal section.
4

4-6
RADIATOR
HANDLING NOTE
Do not remove the radiator cap
when the engine and radiator are
hot. Scalding hot fluid and steam
may be blown out under pressure,
which could cause serious injury.
When the engine has cooled, open
the radiator cap by the following
procedure:
Place a thick rag, like a towel, over
the radiator cap, slowly rotate the
cap counterclockwise to the de-
tent. This procedure allows any re-
sidual pressure to escape. When
the hissing sound has stopped,
press down on the cap while turn-
ing counterclockwise and remove
it.
CHECKING THE RADIATOR
1. Inspect:• Radiator core "1"
Obstruction →Blow out with com-
pressed air through rear of the ra-
diator.
Bent fin →Repair/replace.
INSTALLING THE RADIATOR
1. Install: • O-ring "1"
• Radiator pipe 1 "2"
• Bolt (radiator pipe) "3"
Apply the lithium soap base grease
on the O-ring.
2. Install:• Radiator breather hose "1"
• Radiator hose 2 "2"
• Radiator hose 4 "3"
• Pipe "4"
• Radiator hose 5 "5"
• Radiator hose 3 "6"To right radiator "7".
3. Install: • Right radiator "1"
• Bolt (right radiator) "2"
• Radiator hose 5 "3"
Refer to "CABLE ROUTING DIA-
GRAM" section in the CHAPTER
2.
4. Install: • Left radiator "1"
• Bolt (left radiator) "2"
• Radiator hose 1 "3"
Refer to "CABLE ROUTING DIA-
GRAM" section in the CHAPTER
2.
5. Tighten:
• Radiator hose clamp "4" 6. Install:
• Radiator guard "1"
First fit the inner hook portion "a" and
then the outer one "b" onto the radia-
tor.
Bolt (radiator pipe):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (right radiator):10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (left radiator): 10 Nm (1.0 m•kg, 7.2
ft•lb)
Radiator hose 1: 2 Nm (0.2 m•kg, 1.4
ft•lb)
Radiator hose clamp: 2 Nm (0.2 m•kg, 1.4
ft•lb)

4-10
CARBURETOR
HANDLING NOTE
Do not loosen the screw (throttle
position sensor) "1" except when
changing the throttle position sen-
sor due to failure because it will
cause a drop in engine perfor-
mance.
REMOVING THE PILOT SCREW
1. Remove: • Pilot screw "1"
To optimize the fuel flow at a small
throttle opening, each machine's pilot
screw has been individually set at the
factory. Before removing the pilot
screw, turn it in fully and count the
number of turns. Record this number
as the factory-set number of turns
out.
CHECKING THE CARBURETOR
1. Inspect:
• Carburetor bodyContamination →Clean.
• Use a petroleum based solvent for
cleaning. Blow out all passages and
jets with compressed air.
• Never use a wire.
2. Inspect:
•Main jet "1"
• Pilot jet "2"
• Needle jet "3"
• Starter jet "4"
•Pilot air jet "5"
• Leak jet "6"Damage →Replace.
Contamination →Clean.
• Use a petroleum based solvent for
cleaning. Blow out all passages and
jets with compressed air.
• Never use a wire.
CHECKING THE NEEDLE VALVE
1. Inspect: • Needle valve "1"
• Valve seat "2"
Grooved wear "a" →Replace.
Dust "b" →Clean.
• Filter "c"
Clogged →Clean.
CHECKING THE THROTTLE
VALVE
1. Check: • Free movementStick →Repair or replace.
Insert the throttle valve "1" into the
carburetor body, and check for free
movement.
CHECKING THE JET NEEDLE
1. Inspect: • Jet needle "1"Bends/wear →Replace.
• Clip groove Free play exists/wear →Replace.
• Clip position
MEASURING AND ADJUSTING
THE FLOAT HEIGHT
1. Measure: • Float height "a"Out of specification →Adjust.
Measurement and adjustment
steps:
a. Hold the carburetor in an upside
down position.
• Slowly tilt the ca rburetor in the op-
posite direction, then take the mea-
surement when the needle valve
aligns with the float arm.
• If the carburetor is level, the weight of the float will push in the needle
valve, resulting in an incorrect mea-
surement.
b. Measure the distance between the mating surface of the float
chamber and top of the float using
a vernier calipers.
The float arm should be resting on the
needle valve, but not compressing
the needle valve.
Standard clip position: No.4 Groove
Float height: 8.0 mm (0.31 in)

4-17
CAMSHAFTS
4. Measure:• Camshaft-to-cap clearanceOut of specification →Measure
camshaft outside diameter.
Measurement steps:
a. Install the camshaft onto the cylin- der head.
b. Position a strip of Plastigauge
®
"1" onto the camshaft.
c. Install the clip, dowel pins and camshaft caps.
• Tighten the bolts (camshaft cap) in a crisscross pattern from innermost
to outer caps.
• Do not turn the camshaft when
measuring clearance with the
Plastigauge
®.
d. Remove the camshaft caps and measure the width of the Plasti-
gauge
® "1".
5. Measure:• Camshaft outside diameter "a"
Out of specification →Replace the
camshaft.
Within specification →Replace
camshaft case and camshaft
caps as a set. CHECKING THE CAMSHAFT
SPROCKET
1. Inspect:
• Camshaft sprocket "1"Wear/damage →Replace the
camshaft assemb ly and timing
chain as a set.
CHECKING THE
DECOMPRESSION SYSTEM
1. Check: • Decompression system
Checking steps:
a. Check that the decompression
mechanism cam "1" moves
smoothly.
b. Check that the decompression
mechanism cam lever pin "2" proj-
ects from the camshaft.
CHECKING THE TIMING CHAIN
TENSIONER
1. Check:• While pressing the tensioner rod lightly with fingers, use a thin
screwdriver "1" and wind the ten-
sioner rod up fully clockwise.
• When releasing the screwdriver
by pressing lightly with fingers,
make sure that the tensioner rod
will come out smoothly.
• If not, replace the tensioner as- sembly. INSTALLING THE CAMSHAFT
1. Install:
• Exhaust camshaft "1"
• Intake camshaft "2"
Installation steps:
a. Turn the crankshaft counterclock- wise with a wrench.
• Apply the molybdenum disulfide oil on the camshafts.
• Apply the engine oil on the decom- pression system.
• Squeezing the decompression le-
ver allows the crankshaft to be
turned easily.
b. Align the T.D.C. mark "a" on the rotor with the align mark "b" on the
crankcase cover when piston is at
T.D.C. on compression stroke.
Camshaft-to-cap clear-
ance:
0.028–0.062 mm
(0.0011–0.0024 in)
:0.08 mm (0.003
in)
Bolt (camshaft cap): 10 Nm (1.0 m•kg, 7.2
ft•lb)
Camshaft outside diame-
ter: 21.959–21.972 mm
(0.8645–0.8650 in)