2008 YAMAHA YZ250F seat adjustment

3-1
MAINTENANCE INTERVALS
REGULAR INSPECTION AND ADJUSTMENTS
MAINTENANCE INTERVALS
The following schedule is intended as a general guide to maintenance and lubrication. Bear in mind that such factors as
weather, terrain, geographical location, and individual usage will alter the required maintenance and lubrication intervals. If
you are a doubt as to what intervals to follow in maintaining and lubricating your machine, consult your Yamaha dealer.
Item After
break- in Every
race
Every
third
(or 500 km) Every
fifth (or 1,000 km)
As re-
quired Remarks
ENGINE OIL Replace
●●
Inspect●●
OIL FILTER ELEMENT, OIL
STRAINERClean
●
VALVESCheck the valve clearances
●●The engine must be cold.
Inspect
●Check the valve seats and valve
stems for wear.
Replace
●
VALVE SPRINGS Inspect
●Check the free length and the tilt.
Replace
●
VALVE LIFTERS Inspect
●Check for scratches and wear.
Replace
●
CAMSHAFTS Inspect the camshaft surface.
Inspect
●Inspect the decompression system.
Replace
●
TIMING CHAIN SPROCKETS,
TIMING CHAIN Inspect
●Check for wear on the teeth and for
damage.
Replace
●
PISTON Inspect
●●Inspect crack.
Clean
●Inspect carbon deposits and eliminate
them.
Replace
●
PISTON RING Inspect
●Check ring end gap.
Replace
●●
PISTON PIN Inspect
●
Replace●
CYLINDER HEAD Inspect carbon deposits and eliminate
them.
Inspect and clean
●Change gasket.
3

3-8
ENGINE
2. Apply:• Lithium soap base greaseOn the throttle cable end "a".
3. Install: • Throttle grip cap
• Screw (throttle grip cap)
• Cover (grip cap)
• Cover (throttle cable cap)
ADJUSTING THE HOT STARTER
LEVER FREE PLAY
1. Check: • Hot starter lever free play "a"Out of specification
→Adjust.
2. Adjust: • Hot starter lever free play
Hot starter lever free play adjust-
ment steps:
a. Loosen the locknut "1".
b. Turn the adjuster "2" until free play "a" is within the specified lim-
its.
c. Tighten the locknut.
After adjustment, check proper oper-
ation of hot starter.
CLEANING THE AIR FILTER
ELEMENT
Proper air filter maintenance is the
biggest key to preventing premature
engine wear and damage.
Never run the engine without the
air filter element in place; this
would allow dirt and dust to enter
the engine and cause rapid wear
and possible engine damage.
1. Remove: •Seat
• Fitting bolt "1"
•Washer "2"
• Air filter element "3"
• Air filter guide "4"
2. Clean: • Air filter elementClean them with solvent.
After cleaning, remove the remaining
solvent by squeezing the element.
• Do not twist the element when
squeezing the element.
• Leaving too much of solvent in
the element may result in poor
starting.
3. Inspect:• Air filter element
Damage
→Replace.
4. Apply: • Foam-air-filter oil or equivalent oil
to the element
Squeeze out the excess oil. Element
should be wet but not dripping.
5. Install:• Air filter guide "1"
Align the projection "a" on filter guide
with the hole "b" in air filter element.
6. Apply:• Lithium soap base grease On the matching surface "a" on air
filter element.
7. Install: • Air filter element "1"
• Washer
• Fitting bolt
Align the projection "a" on filter guide
with the hole "b" in air filter case.
CHECKING THE ENGINE OIL
LEVEL
1. Start the engine, warm it up for several minutes, and then turn off
the engine and wait for five min-
utes.
2. Place the machine on a level place and hold it up on upright po-
sition by placing the suitable
stand under the engine.
3. Inspect:
• Oil levelOil should be up to the full level in
the check window "1".
Level check window is not full.
→
Add 0.2 L (0.18 Imp qt, 0.21 US
qt) of oil.
Screw (throttle grip cap):
4 Nm (0.4 m•kg, 2.9
ft•lb)
Hot starter lever free play
"a": 3–6 mm (0.12–0.24 in)
Locknut: 4 Nm (0.4 m•kg, 2.9
ft•lb)
Fitting bolt:
2 Nm (0.2 m•kg, 1.4
ft•lb)

3-10
ENGINE
• Oil hose clamp
9. Install: • Copper washer
• Oil filter element drain bolt
• Crankcase oil drain bolt
• Oil tank drain bolt
• Lower engine guard
10. Fill: • Engine oil
11. Check: • Oil leakage
12. Install: • Oil filler cap
• Washer (oil tank) • Bolt (oil tank)
13. Check: • Engine oil level
CHECKING THE OIL PRESSURE
1. Check: • Oil pressure
Checking steps:
a. Slightly loosen the oil pressure check bolt "1".
b. Start the engine and keep it idling until oil starts to seep from the oil
pressure check bolt. If no oil
comes out after one minute, turn
the engine off so it will not seize.
c. Check oil passages and oil pump for damage or leakage.
d. Start the engine after solving the
problem(s) and recheck the oil
pressure.
e. Tighten the oil pressure check
bolt.
ADJUSTING THE PILOT SCREW
1. Adjust:• Pilot screw "1"
Adjustment steps:
To optimize the fuel flow at a smaller
throttle opening, each machine's pilot
screw has been individually set at the
factory. Before adjusting the pilot
screw, turn it in fully and count the
number of turns. Record this number
as the factory-set number of turns
out.
a. Turn in the pilot screw until it is lightly seated.
b. Turn out the pilot screw by the factory-set number of turns.
ADJUSTING THE ENGINE IDLING
SPEED
1. Start the engine and thoroughly warm it up.
2. Adjust: • Engine idling speed
Adjustment steps:
a. Adjust the pilot screw. Refer to "ADJUSTING THE PI-
LOT SCREW" section.
b. Turn the throttle stop screw "1"
until the specified engine idling
speed.
Using a digital engine tachometer for
idle speed adjustment, detect the en-
gine idling speed by bringing the
sensing element "c" of the engine ta-
chometer close to the ignition coil "2".
Oil hose clamp:2 Nm (0.2 m•kg, 1.4
ft•lb)
Oil filter element drain
bolt: 10 Nm (1.0 m•kg, 7.2
ft•lb)
Crankcase oil drain bolt: 20 Nm (2.0 m•kg, 14
ft•lb)
Oil tank drain bolt: 18 Nm (1.8 m•kg, 13
ft•lb)
Lower engine guard: 10 Nm (1.0 m•kg, 7.2
ft•lb)
Oil quantity: Periodic oil change:1.05 L (0.92 Imp qt,
1.11 US qt)
With oil filter replace-
ment: 1.15 L (1.01 Imp qt,
1.22 US qt)
Total amount:
1.30 L (1.14 Imp qt,
1.37 US qt)Bolt (oil tank): 7 Nm (0.7 m•kg, 5.1
ft•lb)
Oil pressure check bolt: 10 Nm (1.0 m•kg, 7.2
ft•lb)
Pilot screw (example): 2-3/8 turns out
To increase idle speed→Turn the
throttle stop screw "1" in "a".
To decrease idle speed
→Turn
the throttle stop screw "1" out
"b".
Engine idling speed:1,900–2,100 r/min

3-11
ENGINE
ADJUSTING THE VALVE
CLEARANCE
•The valve clearance should be ad-
justed when the engine is cool to
the touch.
• The piston must be at Top Dead Center (T.D.C.) on compression
stroke to check or adjust the valve
clearance.
1. Remove:• Seat
• Fuel tankRefer to "SEAT, FUEL TANK
AND SIDE COVERS" section in
the CHAPTER 4.
2. Remove: • Spark plug
• Cylinder head coverRefer to "CAMSHAFTS" section
in the CHAPTER 4.
3. Remove:
• Timing mark accessing screw "1"
• Crankshaft end accessing screw "2"
• O-ring
4. Check: • Valve clearance
Out of specification
→Adjust.
Checking steps:
a. Turn the crankshaft counterclock- wise with a wrench.
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.
In order to be sure that the piston is at
Top Dead Center, the punch mark "c"
on the exhaust camshaft and the
punch mark "d" on the intake cam-
shaft must align with the cylinder
head surface, as shown in the illustra-
tion.
c. Measure the valve clearance "e"
using a feeler gauge "1".
Record the measured reading if the
clearance is incorrect.
5. Adjust:• Valve clearance
Adjustment steps:
a. Remove the camshaft (intake and exhaust).
Refer to "CAMSHAFTS" section
in the CHAPTER 4.
b. Remove the valve lifters "1" and the pads "2".
•Place a rag in the timing chain
space to prevent pads from falling
into the crankcase.
• Identity each valve lifter and pad
position very carefully so that they
can be reinstalled in their original
place.
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.
Valve clearance (cold):
Intake valve:0.10–0.15 mm
(0.0039–0.0059 in)
Exhaust valve: 0.17–0.22 mm
(0.0067–0.0087 in)
Pad range Pad Availabili-
ty: 25 incre-
ments
No.
120– No.
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

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 carburetor 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.
c. If the float height is not within specification, inspect the valve
seat and needle valve.
d. If either is worn, replace them
both.
e. If both are fine, adjust the float height by bending the float tab "b"
on the float.
Standard clip position:No.5 Groove
Float height:
8.0 mm (0.31 in)

7-7
CHASSIS
C. Stroke
1. Max. oil amount
2. Standard oil amount
3. Min. oil amount
SETTING OF SPRING AFTER
REPLACEMENT
As the front fork setting can be easily
affected by rear suspension, take
care so that the machine front and
rear are balanced (in position, etc.)
when setting the front fork.
1. Use of soft spring • Change the rebound damping.Turn out one or two clicks.
• Change the compression damp-
ing.
Turn in one or two clicks.
Generally a soft spring gives a soft
riding feeling. Rebound damping
tends to become stronger and the
front fork may sink deeply over a se-
ries of gaps.
2. Use of stiff spring• Change the rebound damping.Turn in one or two clicks.
• Change the compression damp-
ing.
Turn out one or two clicks.
Generally a stiff spring gives a stiff
riding feeling. Rebound damping
tends to become weaker, resulting in
lack of a sense of contact with the
road surface or in a vibrating handle-
bar.
FRONT FORK SETTING PARTS
• Front fork spring "1"
The I.D. mark (slits) "a" is proved on the end of the spring.
REAR SUSPENSION SETTING
The rear suspension setting should
be made depending on the rider's
feeling of an actual run and the circuit
conditions.
The rear suspension setting includes
the following two factors:
1. Setting of spring preload
• Change the set length of the spring.
• Change the spring.
2. Setting of damping force • Change the rebound damping.
• Change the compression damp-ing.
CHOOSING SET LENGTH
1. Place a stand or block under the engine to put the rear wheel
above the floor, and measure the
length "a" between the rear wheel
axle center and the rear fender
holding bolt.
2. Remove the stand or block from the engine and with a rider astride
the seat, measure the sunken
length "b" between the rear wheel
axle center and the rear fender
holding bolt. 3. Loosen the locknut "1" and make
adjustment by turning the spring
adjuster "2" to achieve the stan-
dard figure from the subtraction of
the length "b" from the length "a".
• If the machine is new and after it is broken in, the same set length of
the spring may change because of
the initial fatigue, etc. of the spring.
Therefore, be sure to make reeval-
uation.
• If the standard figure cannot be achieved by adjusting the spring
adjuster and changing the spring
set length, replace the spring with
an optional one and make readjust-
ment.
SETTING OF SPRING AFTER
REPLACEMENT
After replacement, be sure to adjust
the spring to the set length [sunken
length 90–100 mm (3.5–3.9 in)] and
set it.
1. Use of soft spring• Set the soft spring for less re-bound damping to compensate
for its less spring load. Run with
the rebound damping adjuster
one or two clicks on the softer
side and readjust it to suit your
preference.
2. Use of stiff spring
• Set the soft spring for more re-bound damping to compensate
for its greater spring load. Run
with the rebound damping adjust-
er one or two clicks on the stiffer
side and readjust it to suit your
preference.
Adjusting the rebound damping will
be followed more or less by a change
in the compression damping. For cor-
rection, turn the low compression
damping adjuster on the softer side.
TY
PE SPRIN
G
RATE SPRING
PART NUM- BER I.D.
MA
RK
(slit
s)
SO FT 0.398 1C3-23141-A1 |
0.408 1C3-23141-B1 ||
0.418 1C3-23141-C1 |||
0.428 1C3-23141-D1 ||||
0.438 1C3-23141-E1 |||||
ST D 0.449 5XC-23141-
N0—
STI FF 0.459 1C3-23141-
G1|-||
0.469 1C3-23141-H1 |-|||
0.479 1C3-23141-J1 |-||||
Standard figure: 90–100 mm (3.5–3.9 in)

7-8
CHASSIS
When using a rear shock absorber
other than currently installed, use
the one whose overall length "a"
does not exceed the standard as it
may result in faulty performance.
Never use one whose overall
length is greater than standard.
REAR SHOCK ABSORBER
SETTING PARTS
• Rear shock spring "1"
[Equal-pitch titanium spring]
[Equal-pitch steel spring][Unequal-pitch steel spring]
Install the spring seat "2" to the ti-
tanium spring.
• The unequal-pitch spring is softer in
initial characteristic than the equal-
pitch spring and is difficult to bottom
out under full compression.
• The I.D. mark "a" is marked at the end of the spring.
• Spring specification varies accord-
ing to the color and quantity of I.D.
marks.
• Extent of adjustment (spring length) [Titanium spring]
[Steel spring]
Length "a" of standard
shock:
490 mm (19.29 in)
T
Y
P
E SPRI
NG
RAT
E SPRING
PART
NUM-
BER -
22212- I.D.
MARK SPR
ING
FRE E
LEN
GTH
(ap-
prox
.)
S
O F
T 4.5 1C3-00 Green 265
4.7 1C3-10 Red 265
4.9 1C3-20 Black 265
5.1 1C3-30 Blue 265
S T
D 5.3
1C3-40
(1C3-A0) Yellow 275
S
TI
F
F 5.5 1C3-50 Pink 275
5.7 1C3-60 White 275
T
Y
P
E SPRI
NG
RAT
E SPRING
PART NUM-
BER -
22212- I.D.
MARK/
Q'TY SPR
ING
FRE E
LEN
GTH
4.3 5UN-00 Brown/1 260
T
Y
P
E SPRI
NG
RAT
E
(ap-
prox. ) SPRING
PART
NUM-
BER -
22212- I.D.
MARK/ Q'TY SPR
ING
FRE E
LEN
GTH
S
O
F
T 4.5 5UN-A0 Green/2 275
4.75UN-B0Red/2275
4.9 5UN-C0 Black/2 275
5.1 5UN-D0 Blue/2 275
5.3 5UN-E0
Yellow/
2 275
5.5 5UN-F0 Pink/2 275
S
TI F
F 5.7
5UN-
22212- G0 White/2 275
SPRING
FREE
LENGTH EXTENT OF AD-
JUSTMENT "b"
Approx. 265 mm
(10.43 in) One I.D. mark
245.5–263.5 mm (9.67–10.37 in)
Two I.D. marks
251.5–269.5 mm (9.90–10.61 in)
Three I.D. marks 243.0–261.0 mm (9.57–10.28 in)
Approx. 275 mm
(10.83 in) One I.D. mark
255.5–273.5 mm (10.06–10.77 in)
Two I.D. marks
261.5–279.5 mm (10.30–11.00 in)
Three I.D. marks 253.0–271.0 mm (9.96–10.67 in)
SPRING FREE
LENGTH EXTENT OF AD-
JUSTMENT "b"
260 mm
(10.24 in) 240.5–258.5 mm
(9.47–10.18 in)
275 mm
(10.83 in) 255.5–273.5 mm
(10.06–10.77 in)

7-9
CHASSIS
SUSPENSION SETTING (FRONT FORK)
• If any of the following symptoms is experienced with the standard position as the base, make resetting by reference to the adjustment procedure given in the same chart.
• Before any change, set the rear shock absorber sunken length to the standard figure 90–100 mm (3.5–3.9 in).
Symptom Section
Check Adjust
Jump Large
gap Medi-
um
gap Small
gap
Stiff over entire
range
○○○
Compression damping Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Oil amount Decrease oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).
Spring Replace with soft spring.
Unsmooth move-
ment over entire
range
○○○○
Outer tube Check for any bends, dents, and other noticeable
scars, etc. If any, replace affected parts.
Inner tube
Slide metal Replace with a new one for extended use.
Piston metal Replace with a new one for extended use.
Under bracket tighten-
ing torque Retighten to specified torque.
Poor initial move-
ment
○
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Oil seal Apply grease in oil seal wall.
Soft over entire
range, bottoming
out
○○
Compression damping Turn adjuster clockwise (about 2 clicks) to in- crease damping.
Oil amount Increase oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).
Spring Replace with stiff spring.
Stiff toward stroke
end
○Oil amount Decrease oil amount by about 5 cm3 (0.2 Imp
oz,0.2 US oz).
Soft toward stroke
end, bottoming out
○Oil amount Increase oil amount by about 5 cm3 (0.2 Imp
oz,0.2 US oz).
Stiff initial move-
ment
○○○○Compression damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Low front, tending to
lower front posture
○○
Compression damping Turn adjuster clockwise (about 2 clicks) to in- crease damping.
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Balance with rear end Set sunken length for 95–100 mm (3.7–3.9 in) when one passenger is astride seat (lower rear
posture).
Oil amount Increase oil amount by about 5 cm
3 (0.2 Imp oz,
0.2 US oz).
"Obtrusive" front,
tending to upper
front posture
○○
Compression damping Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Balance with rear end Set sunken length for 90–95 mm (3.5–3.7 in) when one passenger is astride seat (upper rear
posture).
Spring Replace with soft spring.
Oil amount Decrease oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).