2008 YAMAHA YZ250F Owners Manual

5-5
FRONT WHEEL AND REAR WHEEL
4. Install:•Collar "1"
Apply the lithium soap base grease
on the oil seal lip.
5. Install:• Wheel
Install the brake disc "1" between the
brake pads "2" correctly.
6. Install:• Drive chain "1"
Push the wheel "2" forward and install
the drive chain.
7. Install:• Left drive chain puller "1"
• Wheel axle "2"
• Install the left drive chain puller, and
insert the wheel axle from left side.
• Apply the lithium soap base grease
on the wheel axle.
8. Install:• Right drive chain puller "1"
• Washer "2"
• Nut (wheel axle) "3"
Temporarily tighten the nut (wheel
axle) at this point.
9. Adjust:
• Drive chain slack "a"
Refer to "ADJUSTING THE
DRIVE CHAIN SLACK" section in
the CHAPTER 3.
10. Tighten: • Nut (wheel axle) "1"
• Locknut "2"
Drive chain slack: 48–58 mm (1.9–2.3 in)
Nut (wheel axle): 125 Nm (12.5 m•kg, 90
ft•lb)
Locknut: 19 Nm (1.9 m•kg, 13
ft•lb)

5-6
FRONT BRAKE AND REAR BRAKE
FRONT BRAKE AND REAR BRAKE
REMOVING THE FRONT BRAKEOrder Part name Q'ty Remarks Hold the machine by placing the suitable stand
under the engine. Refer to "HANDLING NOTE".
Drain the brake fluid. Refer to removal section.
1 Brake hose holder (protector) 2
2 Union bolt 2
3Brake hose 1
4 Pad pin plug 1 Remove when loosening the pad pin.
5 Pad pin 1Loosen when disassembling the brake cali-
per.
6 Brake caliper 1
7Brake lever 1
8 Brake master cylinder bracket 1
9 Brake master cylinder 1

5-7
FRONT BRAKE AND REAR BRAKE
REMOVING THE REAR BRAKEOrder Part name Q'ty Remarks Hold the machine by placing the suitable stand
under the engine. Refer to "HANDLING NOTE".
Rear wheel Refer to "FRONT WHEEL AND REAR
WHEEL" section.
Drain the brake fluid. Refer to removal section.
1 Brake pedal 1
2 Brake master cylinder 1
3 Brake hose holder 2
4 Union bolt 2
5Brake hose 1
6 Pad pin plug 1 Remove when loosening the pad pin.
7 Pad pin 1Loosen when disassembling the brake cali-
per.
8 Brake caliper 1

5-8
FRONT BRAKE AND REAR BRAKE
DISASSEMBLING THE BRAKE CALIPEROrder Part name Q'ty Remarks A. Front
B. Rear
AB
1 Pad pin 1 1
2Brake pad 22
3 Pad support 1 1
4 Brake caliper piston 2 1 Refer to removal section.
5 Brake caliper piston dust seal 2 1 Refer to removal section.
6 Brake caliper piston seal 2 1 Refer to removal section.

5-9
FRONT BRAKE AND REAR BRAKE
DISASSEMBLING THE BRAKE MASTER CYLINDEROrder Part name Q'ty Remarks A. Front
B. Rear
1 Brake master cylinder cap 1
2 Diaphragm 1
3 Reservoir float 1
4 Push rod (Front) 1
5 Brake master cylinder boot 1
6 Circlip 1 Use a long nose circlip pliers.
7 Washer 1
8 Push rod (Rear) 1
9 Brake master cylinder kit 1

5-10
FRONT BRAKE AND REAR BRAKE
HANDLING NOTE
Support the machine securely so
there is no danger of it falling over.
DRAINING THE BRAKE FLUID
1. Remove:• Brake master cylinder cap "1"
• Protector (rear brake)
Do not remove the diaphragm.
A. Front
B. Rear
2. Connect the transparent hose "2" to the bleed screw "1" and place a
suitable container under its end.
A. Front
B. Rear
3. Loosen the bleed screw and drain the brake fluid while pulling the le-
ver in or pushing down on the
pedal.
• Do not reuse the drained brake
fluid.
• Brake fluid may erode painted
surfaces or plastic parts. Always
clean up spilled fluid immediate-
ly.
REMOVING THE BRAKE CALIPER
PISTON
1. Remove:• Brake caliper pistonUse compressed air and proceed
carefully.
• Cover piston with rag and use ex-treme caution when expelling
piston from cylinder.
• Never attempt to pry out piston.
Caliper piston removal steps:
a. Insert a piece of rag into the brake caliper to lock one brake caliper.
b. Carefully force the piston out of the brake caliper cylinder with
compressed air.
A. Front
B. Rear
REMOVING THE BRAKE CALIPER
PISTON SEAL KIT
1. Remove:
• Brake caliper piston dust seal "1"
• Brake caliper piston seal "2"
Remove the brake caliper piston
seals and brake caliper piston dust
seals by pushing them with a finger.
Never attempt to pry out brake cal-
iper piston seals and brake caliper
piston dust seals.
Replace the brake caliper piston
seals and brake caliper piston dust
seals whenever a caliper is disas-
sembled.
A. Front
B. Rear
CHECKING THE BRAKE MASTER
CYLINDER
1. Inspect: • Brake master cylinder inner sur-
face "a"
Wear/scratches
→ Replace mas-
ter cylinder assembly.
Stains
→Clean.
Use only new brake fluid.
A. Front
B. Rear
2. Inspect: • Diaphragm "1"Crack/damage
→Replace.
A. Front
B. Rear
3. Inspect: (front brake only)
• Reservoir float "1"Damage
→Replace.
4. Inspect: • Brake master cylinder piston "1"
• Brake master cylinder cup "2"Wear/damage/score marks
→Re-
place brake master cylinder kit.

5-11
FRONT BRAKE AND REAR BRAKE
CHECKING THE BRAKE CALIPER
1. Inspect:• Brake caliper cylinder inner sur-face "a"
Wear/score marks
→Replace
brake caliper assembly.
A. Front
B. Rear
2. Inspect: • Brake caliper piston "1"
Wear/score marks
→Replace
brake caliper piston assembly.
Replace the brake caliper piston
seals and brake caliper piston dust
seals "2" whenever a caliper is dis-
assembled.
CHECKING THE BRAKE HOSE
1. Inspect: •Brake hose "1"Crack/damage
→Replace.
HANDLING NOTE
• All internal parts should be cleaned in new brake fluid only.
• Internal parts should be lubricat-
ed with brake fluid when in-
stalled.
• Replace the brake caliper piston seals and brake caliper piston
dust seals whenever a caliper is
disassembled.
INSTALLING THE BRAKE
CALIPER PISTON
1. Clean:
• Brake caliper
• Brake caliper piston seal
• Brake caliper piston dust seal
• Brake caliper piston
Clean them with brake fluid.
2. Install: • Brake caliper piston seal "1"
• Brake caliper piston dust seal "2"
Always use new brake caliper pis-
ton seals and brake caliper piston
dust seals.
• Apply the brake fluid on the brake caliper piston seal.
• Apply the silicone grease on the brake caliper piston dust seal.
• Fit the brake caliper piston seals and brake caliper piston dust seals
onto the slot on brake caliper cor-
rectly.
A. Front
B. Rear
3. Install:
• Brake caliper piston "1"
Apply the brake fluid on the piston
wall.
• Install the piston with its shallow depressed side "a" facing the
brake caliper.
• Never force to insert.
A. Front
B. Rear
INSTALLING THE FRONT BRAKE
CALIPER
1. Install: • Pad support "1"
• Brake pad "2"
• Pad pin "3"
• Install the brake pads with their pro-jections "a" into the brake caliper re-
cesses "b".
• Temporarily tighten the pad pin at this point.
2. Install:
• Brake caliper "1"
• Bolt (brake caliper) "2"
3. Tighten: • Pad pin "3"
4. Install: • Pad pin plug "4"
Bolt (brake caliper): 28 Nm (2.8 m•kg, 20
ft•lb)
Pad pin: 18 Nm (1.8 m•kg, 13
ft•lb)
Pad pin plug: 3 Nm (0.3 m•kg, 2.2
ft•lb)

5-12
FRONT BRAKE AND REAR BRAKE
INSTALLING THE REAR BRAKE
CALIPER
1. Install:• Pad support "1"
• Brake pad "2"
• Pad pin "3"
• Install the brake pads with their pro-jections "a" into the brake caliper re-
cesses "b".
• Temporarily tighten the pad pin at this point.
2. Install:
• Brake disc cover "1"
• Bolt (brake disc cover) "2"
3. Install: • Brake caliper "1"
• Rear wheel "2"Refer to "FRONT WHEEL AND
REAR WHEEL" section.
4. Tighten: • Pad pin "3"
5. Install: • Pad pin plug "4" INSTALLING THE BRAKE
MASTER CYLINDER KIT
1. Clean:
• Brake master cylinder
• Brake master cylinder kit
Clean them with brake fluid.
2. Install:
• Brake master cylinder cup (prima-ry) "1"
• Brake master cylinder cup (sec-
ondary) "2"
To brake master cylinder piston
"3".
Apply the brake fluid on the brake
master cylinder cup.
After installing, cylinder cup
should be installed as shown di-
rection. Wrong installation cause
improper brake performance.
3. Install:• Spring "1"To brake master cylinder piston
"2".
Install the spring at the smaller dia.
side.
4. Install:
• Brake master cylinder kit "1"
• Washer (front brake) "2"
• Push rod (rear brake) "2"
•Circlip "3"
• Brake master cylinder boot "4"
• Push rod (front brake) "5"To brake master cylinder.
• Apply the brake fluid on the brake master cylinder kit.
• Apply the silicone grease on the tip
of the push rod.
• When installing the circlip, use a long nose circlip pliers.
A. Front
B. Rear
INSTALLING THE FRONT BRAKE
MASTER CYLINDER
1. Install: • Brake master cylinder "1"
• Brake master cylinder bracket "2"
• Bolt (brake master cylinder brack-et) "3"
• Install the bracket so that the arrow mark "a" face upward.
• First tighten the bolts on the upper
side of the brake master cylinder
bracket, and then tighten the bolts
on the lower side.
Bolt (brake disc cover): 10 Nm (1.0 m•kg, 7.2
ft•lb)
Pad pin: 18 Nm (1.8 m•kg, 13
ft•lb)
Pad pin plug: 3 Nm (0.3 m•kg, 2.2
ft•lb)
Bolt (brake master cylin-
der bracket):9 Nm (0.9 m•kg, 6.5
ft•lb)