2008 YAMAHA YZ250F ABS

3-5
PRE-OPERATION INSPECTION AND MAINTENANCE
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating condition.
Before using this machine, check the following points.
GENERAL INSPECTION AND MAINTENANCEItem RoutinePage
Coolant Check that coolant is filled up to the radiator cap. Check the cool-
ing system for leakage. P.3-6 – 7
Fuel Check that a fresh gasoline is filled in the fuel tank. Check the fuel
line for leakage. P.1-8 – 9
Engine oil Check that the oil level is correct. Check the crankcase and oil line
for leakage. P.3-8 – 10
Gear shifter and clutch Check that gears can be shifted correctly in order and that the
clutch operates smoothly. P.3-7
Throttle grip/Housing Check that the throttle grip operation and free play are correctly
adjusted. Lubricate the throttle grip and housing, if necessary. P.3-7 – 8
Brakes Check the play of front brake and effect of front and rear brake. P.3-14 – 16
Drive chain Check drive chain slack and alignment. Check that the drive chain
is lubricated properly. P.3-17
Wheels Check for excessive wear and tire pressure. Check for loose
spokes and have no excessive play. P.3-20
Steering Check that the handlebar can be turned smoothly and have no ex-
cessive play. P.3-20 – 21
Front forks and rear shock
absorber Check that they operate smoothly and there is no oil leakage.
P.3-18 – 20
Cables (wires) Check that the clutch and throttle cables move smoothly. Check
that they are not caught when the handlebars are turned or when
the front forks travel up and down.
—
Exhaust pipe Check that the exhaust pipe is tightly mounted and has no cracks. P.4-3 – 4
Rear wheel sprocket Check that the rear wheel sprocket tightening bolt is not loose. P.3-16 – 17
Lubrication Check for smooth operation. Lubricate if necessary. P.3-22
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P.1-11
Lead connectors Check that the CDI magneto, CDI unit, and ignition coil are con-
nected tightly. P.1-3
Settings Is the machine set suitably for the condition of the racing course
and weather or by taking into account the results of test runs be-
fore racing? Are inspection and maintenance completely done?
P.7-1 – 10

3-18
CHASSIS
CHECKING THE FRONT FORK
1. Inspect:• Front fork smooth actionOperate the front brake and
stroke the front fork.
Unsmooth action/oil leakage
→
Repair or replace.
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, relieve 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 force
By 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.
ADJUSTING THE FRONT FORK
COMPRESSION DAMPING FORCE
1. Adjust:• Compression damping force
By 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.
CHECKING THE REAR SHOCK
ABSORBER
1. Inspect:• Swingarm smooth action
Abnormal noise/unsmooth action
→Grease the pivoting points or
repair the pivoting points.
Damage/oil leakage
→Replace.
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: 11 clicks out
* 10 clicks out
* For EUROPE
Stiffer "a" →Increase the com-
pression damping force. (Turn
the adjuster "1" in.)
Softer "b"
→Decrease the com-
pression damping force. (Turn
the adjuster "1" out.)
Extent of adjustment:
Maximum Minimum
Fully turned in
position 20 clicks out
(from maximum
position)
Standard position: 9 clicks out
* 10 clicks out
* For EUROPE

3-19
CHASSIS
ADJUSTING THE REAR SHOCK
ABSORBER SPRING PRELOAD
1. Elevate the rear wheel by placing the suitable stand under the en-
gine.
2. Remove: • Rear frame
3. Loosen: • Locknut "1"
4. Adjust:
• Spring preloadBy turning the adjuster "2".
•Be sure to remove all dirt and mud
from around the locknut and adjust-
er before adjustment.
• The length of the spring (installed) changes 1.5 mm (0.06 in) per turn of the adjuster.
• The I.D. mark "b" is marked at the end of the spring.
• The standard length and extent of
adjustment vary according to the
quantity of I.D. marks.
Never attempt to turn the adjuster
beyond the maximum or minimum
setting.
5. Tighten:• Locknut
6. Install: • Rear frame (upper)
• Rear frame (lower)
ADJUSTING THE REAR SHOCK
ABSORBER 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.
(Which align the punch mark "a"
on the adjuster with the punch
mark "b" on the bracket.)
Do not force the adjuster past the
minimum or maximum extent of
adjustment. The adjuster may be
damaged.
ADJUSTING THE REAR SHOCK
ABSORBER LOW COMPRESSION
DAMPING FORCE
1. Adjust:• Low compression damping forceBy turning the adjuster "1".
Stiffer
→Increase the spring pre-
load. (Turn the adjuster "2" in.)
Softer
→Decrease the spring pre-
load. (Turn the adjuster "2"
out.)
Spring length (installed)
"a":
Standard length Extent of ad-
justment
One I.D. mark 268 mm
(10.55 in)
*262 mm
(10.31 in)
Two I.D. marks 274 mm
(10.79 in)
*268 mm
(10.55 in)
Three I.D.
marks 265.5 mm
(10.45 in)
*259.5 mm
(10.22 in) 255.5–273.5
mm (10.06–
10.77 in)
261.5–279.5
mm (10.30–
11.00 in)
253.0–271.0
mm (9.96–10.67
in)
* For EUROPE
Rear frame (upper): 38 Nm (3.8 m•kg, 27
ft•lb)
Rear frame (lower): 32 Nm (3.2 m•kg, 23
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: About 8 clicks out
Stiffer "a"
→Increase the low
compression damping force.
(Turn the adjuster "1" in.)
Softer "b"
→Decrease the low
compression damping force.
(Turn the adjuster "1" out.)
Extent of adjustment:
Maximum Minimum
Fully turned in
position 20 clicks out
(from maximum
position)

3-20
CHASSIS
• STANDARD POSITION:This is the position which is back
by the specific number of clicks
from the fully turned-in position.
(Which align the punch mark "a"
on the adjuster with the punch
mark "b" on the high compression
damping adjuster.)
Do not force the adjuster past the
minimum or maximum extent of
adjustment. The adjuster may be
damaged.
ADJUSTING THE REAR SHOCK
ABSORBER HIGH COMPRESSION
DAMPING FORCE
1. Adjust:• High compression damping force
By turning the adjuster "1".
• STANDARD POSITION: This is the position which is back
by the specific number of turns
from the fully turned-in position.
(Which align the punch mark "a"
on the adjuster with the punch
mark "b" on the adjuster body.)
Do not force the adjuster past the
minimum or maximum extent of
adjustment. The adjuster may be
damaged.
CHECKING THE TIRE PRESSURE
1. Measure:
• Tire pressureOut of specification
→Adjust.
•Check the tire while it is cold.
• Loose bead stoppers allow the tire
to slip off its position on the rim
when the tire pressure is low.
• A tilted tire valve stem indicates that
the tire slips off its position on the
rim.
• If the tire valve stem is found tilted,
the tire is considered to be slipping
off its position. Correct the tire posi-
tion.
CHECKING AND TIGHTENING THE
SPOKES
1. Inspect:• Spokes "1"Bend/damage
→Replace.
Loose spoke
→Retighten.
2. Tighten: •Spokes
Be sure to retighten these spokes be-
fore and after break-in. After a prac-
tice or a race check spokes for
looseness.
CHECKING THE WHEELS
1. Inspect:
• Wheel runoutElevate the wheel and turn it.
Abnormal runout
→ Replace.
2. Inspect: • Bearing free play
Exist play
→Replace.
CHECKING AND ADJUSTING THE
STEERING HEAD
1. Elevate the front wheel by placing a suitable stand under the engine.
2. Check:
• Steering stemGrasp the bottom of the forks and
gently rock the fork assembly
back and forth.
Free play
→Adjust steering head.
Standard position:
About 8 clicks out
Stiffer "a"
→Increase the high
compression damping force.
(Turn the adjuster "1" in.)
Softer "b"
→Decrease the high
compression damping force.
(Turn the adjuster "1" out.)
Extent of adjustment:
Maximum Minimum
Fully turned in
position 2 turns out
(from maximum
position)
Standard position:
About 1-1/2 turns out
Standard tire pressure: 100 kPa (1.0 kgf/cm
2,
15 psi)
Spokes: 3 Nm (0.3 m•kg, 2.2
ft•lb)

4-7
CARBURETOR
CARBURETOR
REMOVING THE CARBURETOROrder Part name Q'ty Remarks Seat and fuel tank Refer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
Rear shock absorber Refer to "REAR SHOCK ABSORBER" sec-
tion in the CHAPTER 5.
1Clamp 1
2 Throttle position sensor lead coupler 1
3 Throttle cable cover 1
4 Throttle cable 2
5 Clamp (air filter joint) 1 Loosen the screw (air filter joint).
6 Clamp (carburetor joint) 1 Loosen the screws (carburetor joint).
7 Hot starter plunger 1
8 Carburetor assembly 1
9 Carburetor joint 1
4 Nm (0.4 m kg, 2.9 ft lb)
4 Nm (0.4 m kg, 2.9 ft lb)
2 Nm (0.2 m kg, 1.4 ft lb)
3 Nm (0.3 m kg, 2.2 ft lb)
3 Nm (0.3 m kg, 2.2 ft lb)
11 Nm (1.1 m kg, 8.0 ft lb)
10 Nm (1.0 m kg, 7.2 ft lb)

5-14
FRONT BRAKE AND REAR BRAKE
4. Install:• Copper washer "1"
•Brake hose "2"
• Union bolt "3"
Always use new copper washers.
Install the brake hose so that its
pipe portion "a" directs as shown
and lightly touches the projection
"b" on the brake master cylinder.
INSTALLING THE REAR BRAKE
HOSE
1. Install:• Copper washer "1"
•Brake hose "2"
• Union bolt "3"
Always use new copper washers.
Install the brake hose so that its
pipe portion "a" directs as shown
and lightly touches the projection
"b" on the brake caliper.
2. Install:• Brake hose holder "1"
• Screw (brake hose holder) "2"
After installing the brake hose
holders, make sure the brake hose
does not contact the spring (rear
shock absorber). If it does, correct
its twist.
FILLING THE BRAKE FLUID
1. Fill:•Brake fluid
Until the fluid level reaches
"LOWER" level line "a".
• Use only the designated quality brake fluid:
otherwise, the rubber seals may
deteriorate, causing leakage and
poor brake performance.
• Refill with the same type of brake
fluid;
mixing fluids may result in a
harmful chemical reaction and
lead to poor performance.
• Be careful that water does not enter the master cylinder when
refilling. Water will significantly lower the boiling point of the flu-
id and may result in vapor lock.
Brake fluid may erode painted sur-
faces or plastic parts. Always
clean up spilled fluid immediately.
A. Front
B. Rear
2. Air bleed: • Brake system
Refer to "BLEEDING THE HY-
DRAULIC BRAKE SYSTEM" sec-
tion in the CHAPTER 3.
3. Inspect: • Brake fluid levelFluid at lower level
→Fill up.
Refer to "CHECKING THE
BRAKE FLUID LEVEL" section in
the CHAPTER 3.
4. Install: • Reservoir float (front brake)
• Diaphragm
• Brake master cylinder cap "1"
• Screw (brake master cylinder cap) "2"
After installation, while pulling the
brake lever in or pushing down on
the brake pedal, check whether
there is any brake fluid leaking
where the union bolts are installed
respectively at the brake master
cylinder and brake caliper.
Union bolt:
30 Nm (3.0 m•kg, 22
ft•lb)
Union bolt: 30 Nm (3.0 m•kg, 22
ft•lb)
Screw (brake hose hold-
er):2 Nm (0.2 m•kg, 1.4
ft•lb)
Recommended brake flu-
id: DOT #4
Screw (bolt) {brake mas-
ter cylinder cap}:2 Nm (0.2 m•kg, 1.4
ft•lb)

5-32
SWINGARM
SWINGARM
REMOVING THE SWINGARMOrder Part name Q'ty Remarks Hold the machine by placing the suitable stand
under the engine. Refer to "HANDLING NOTE".
Brake hose holder Refer to "FRONT BRAKE AND REAR
BRAKE" section.
Rear brake caliper Refer to "FRONT BRAKE AND REAR
BRAKE" section.
Bolt (brake pedal) Shift the brake pedal backward.
Drive chain
1 Drive chain support 1
2 Lower chain tensioner 1
3 Bolt (rear shock absorber-relay arm) 1 Hold the swingarm.
4 Bolt (connecting rod) 1
5Pivot shaft 1
6 Swingarm 1

5-35
SWINGARM
INSTALLING THE SWINGARM
1. Install:• Bushing "1"
• Thrust bearing "2"
•Oil seal "3"
•Collar "4"To swingarm "5".
Apply the molybdenum disulfide
grease on the bushings, thrust bear-
ings, oil seal lips and contact surfaces
of the collar and thrust bearing.
2. Install:
•Collar "1"
• Washer "2"To relay arm "3".
Apply the molybdenum disulfide
grease on the collars and oil seal lips.
3. Install:•Collar "1"To connecting rod "2".
Apply the molybdenum disulfide
grease on the collar and oil seal lips.
4. Install:• Connecting rod "1"
• Bolt (connecting rod) "2" •Washer "3"
• Nut (connecting rod) "4"
To relay arm "5".
Apply the molybdenum disulfide
grease on the bolt.
5. Install:• Relay arm "1"
• Bolt (relay arm) "2"
•Washer "3"
• Nut (relay arm) "4"To swingarm.
• Apply the molybdenum disulfide grease on the bolt circumference
and threaded portion.
• Do not tighten the nut yet.
6. Install: • Swingarm "1"
• Pivot shaft "2"
• Apply the molybdenum disulfide
grease on the pivot shaft.
• Insert the pivot shaft from right side.
7. Check: • Swingarm side play "a"Free play exists
→Replace thrust
bearing. • Swingarm up and down move-
ment "b"
Unsmooth movement/binding/
rough spots
→Grease or replace
bearings, bushings and collars.
8. Install: • Bolt (connecting rod) "1"
• Washer "2"
• Nut (connecting rod) "3"
• Apply the molybdenum disulfide grease on the bolt.
• Do not tighten the nut yet.
9. Install: • Bolt (rear shock absorber-relay
arm) "1"
• Nut (rear shock absorber-relay arm) "2"
Apply the molybdenum disulfide
grease on the bolt.
10. Tighten:• Nut (connecting rod) "1"
Nut (connecting rod):
80 Nm (8.0 m•kg, 58
ft•lb)
Pivot shaft: 85 Nm (8.5 m•kg, 61
ft•lb)
Nut (rear shock absorb-
er-relay arm):53 Nm (5.3 m•kg, 38
ft•lb)
Nut (connecting rod): 80 Nm (8.0 m•kg, 58
ft•lb)