YAMAHA YZ250F 2008 Owners Manual

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)

5-13
FRONT BRAKE AND REAR BRAKE
2. Install:• Brake lever "1"
• Bolt (brake lever) "2"
• Nut (brake lever) "3"
Apply the silicone grease on the
brake lever sliding surface, bolt and
tip of the push rod.
INSTALLING THE REAR BRAKE
MASTER CYLINDER
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 master cylinder.
2. Install:• Brake master cylinder "1" • Bolt (brake master cylinder) "2"
3. Install: • Spring "1"
• Brake pedal "2"
• O-ring "3"
• Bolt (brake pedal) "4"
•Clip "5"
Apply the lithium soap base grease
on the bolt, O-ring and brake pedal
bracket.
4. Install:•Pin "1"
•Washer "2"
• Cotter pin "3"
After installing, check the brake pedal
height. Refer to "ADJUSTING THE
REAR BRAKE" section in the CHAP-
TER 3.
INSTALLING THE FRONT 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"
• Nut (brake hose holder) "2"
Align the top "a" of the brake hose
holder with the paint "b" of the brake
hose.
3. Pass the brake hose through the
cable guide "1".
Bolt (brake lever):
6 Nm (0.6 m•kg, 4.3
ft•lb)
Nut (brake lever): 6 Nm (0.6 m•kg, 4.3
ft•lb)
Union bolt: 30 Nm (3.0 m•kg, 22
ft•lb)
Bolt (brake master cylin-
der):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (brake pedal): 26 Nm (2.6 m•kg, 19
ft•lb)Union bolt:
30 Nm (3.0 m•kg, 22
ft•lb)
Nut (brake hose holder): 7 Nm (0.7 m•kg, 5.1 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)

5-15
FRONT BRAKE AND REAR BRAKE
A. Front
B. Rear
5. Install: (rear brake only)
• Protector "1"
• Bolt (protector) "2"
Bolt (protector):7 Nm (0.7 m•kg, 5.1
ft•lb)

5-16
FRONT FORK
FRONT FORK
REMOVING THE FRONT FORKOrder Part name Q'ty Remarks Hold the machine by placing the suitable stand
under the engine. Refer to "HANDLING NOTE".
Front wheel Refer to "FRONT WHEEL AND REAR
WHEEL" section.
Front brake caliper Refer to "FRONT BRAKE AND REAR
BRAKE" section.
Number plate Refer to "SEAT, FUEL TANK AND SIDE
COVERS" section in the CHAPTER 4.
1Protector 1
2 Pinch bolt (upper bracket) 2 Only loosening.
3 Damper assembly 1Loosen when disassembling the front fork.
Refer to removal section.
4 Pinch bolt (lower bracket) 2 Only loosening.
5 Front fork 1
21 Nm (2.1 m kg, 15 ft lb)
21 Nm (2.1 m kg, 15 ft lb)
5 Nm (0.5 m kg, 3.6 ft lb)
5 Nm (0.5 m kg, 3.6 ft lb)
7 Nm (0.7 m kg, 5.1 ft lb)

5-17
FRONT FORK
DISASSEMBLING THE FRONT FORKOrder Part name Q'ty Remarks1 Adjuster 1 Drain the fork oil. Refer to removal section.
2 Fork spring 1 Drain the fork oil.
3 Dust seal 1 Refer to removal section.
4 Stopper ring 1 Refer to removal section.
5 Inner tube 1 Refer to removal section.
6 Outer tube 1
7 Piston metal 1
8 Slide metal 1
9 Oil seal washer 1
10 Oil seal 1
11 Base valve 1 Drain the fork oil. Refer to removal section.
12 Damper assembly 1 Drain the fork oil. Refer to removal section.
30 Nm (3.0 m kg, 22 ft lb)
29 Nm (2.9 m kg, 21 ft lb)
29 Nm (2.9 m kg, 21 ft lb)
1 Nm (0.1 m kg, 0.7 ft lb)
55 Nm (5.5 m kg, 40 ft lb)

5-18
FRONT FORK
HANDLING NOTE
Support the machine securely so
there is no danger of it falling over.
The front fork requires careful atten-
tion. So it is recommended that the
front fork be maintained at the deal-
ers.
To prevent an accidental explosion
of air, the following instructions
should be observed:
• The front fork with a built-in pis-ton rod has a very sophisticated
internal construction and is par-
ticularly sensitive to foreign ma-
terial. Use enough care not to
allow any foreign material to
come in when the oil is replaced
or when the front fork is disas-
sembled and reassembled.
• Before removing the base valves or front forks, be sure to extract
the air from the air chamber com-
pletely.
REMOVING THE DAMPER
ASSEMBLY
1. Loosen:
• Damper assembly "1"
Before removing the front fork from
the machine, loosen the damper as-
sembly with the cap bolt ring wrench
"2".
REMOVING THE ADJUSTER
1. Drain the outer tube of its front fork oil at its top.
2. Loosen: •Adjuster "1" 3. Remove:
• Adjuster "1"
• While compressing the inner tube "2", set the cap bolt ring wrench "4"
between the inner tube and locknut
"3".
• Hold the locknut and remove the adjuster.
Do not remove the locknut as the
damper rod may go into the damp-
er assembly and not be taken out.
REMOVING THE INNER TUBE
1. Remove:
• Dust seal "1"
• Stopper ring "2"Using slotted-head screwdriver.
Take care not to scratch the inner
tube.
2. Remove:• Inner tube "1"
Oil seal removal steps:
a. Push in slowly "a" the inner tube just before it bottoms out and then
pull it back quickly "b".
b. Repeat this step until the inner tube can be pulled out from the
outer tube.
REMOVING THE BASE VALVE
1. Remove:• Base valve "1"
From damper assembly "2".
Hold the damper assembly with the
cap bolt ring wrench "3" and use the
cap bolt wrench "4" to remove the
base valve.
CHECKING THE DAMPER
ASSEMBLY
1. Inspect:• Damper assembly "1"Bend/damage
→ Replace.
• O-ring "2"
Wear/damage
→ Replace.
The front fork with a built-in piston
rod has a very sophisticated inter-
nal construction and is particularly
sensitive to foreign material.
Use enough care not to allow any
foreign material to come in when
the oil is replaced or when the
front fork is disassembled and re-
assembled.Cap bolt ring wrench: YM-01501/90890-01501
Cap bolt ring wrench:YM-01501/90890-01501
Cap bolt wrench:
YM-01500/90890-01500
Cap bolt ring wrench:
YM-01501/90890-01501