warning YAMAHA YZ250F 2001 Owner's Manual

5 - 4
CHAS

FRONT WHEEL AND REAR WHEEL
EC514200
Wheel axle
1. Measure:
l
Wheel axle bends
Out of specification
®
Replace.
Use the dial gauge
1
.
NOTE:

The bending value is shown by one half of the
dial gauge reading.
WARNING

Do not attempt to straighten a bent axle.
Wheel axle bending limit:
0.5 mm (0.020 in)
EC594200
Brake disc
1. Measure:
l
Brake disc deflection (only rear brake
disc)
Use the dial gauge
1
.
Out of specification
®
Inspect wheel
runout.
If wheel runout is in good condition,
replace the brake disc.
2. Measure:
l
Brake disc thickness
a

Out of limit
®
Replace.
Brake disc deflection limit:
Rear:
: 0.15 mm (0.006 in)
Brake disc thickness:
Front:
3.0 mm (0.12 in)
: 2.5 mm (0.10 in)
Rear:
4.0 mm (0.16 in)
: 3.5 mm (0.14 in)

5 - 10
CHASFRONT BRAKE AND REAR BRAKE
EC5A0000
FRONT BRAKE AND REAR BRAKE
EC5A8000
FRONT BRAKE
Extent of removal:1 Brake hose removal2 Brake caliper removal
3 Brake master cylinder removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removalFRONT BRAKE REMOVAL
Hold the machine by placing the
suitable stand under the engine.
Drain the brake fluid.
WARNING
Support the machine securely so there is nodanger of it falling over.
Refer to “REMOVAL POINTS”.
1 Brake hose cover 1
2 Brake hose holder 1
3 Bolt (brake hose holder) 2 Only loosening.
4 Union bolt 2
5 Brake hose 1
6 Pad pin plug 1 Remove when loosening the pad pin.
7 Pad pin 1 Loosen when disassembling the caliper.
8 Brake caliper 1
9 Brake lever 1
10 Brake master cylinder bracket 1
11 Brake master cylinder 1
2
3
1
3
2

5 - 11
CHAS
EC5A8100
REAR BRAKE
Extent of removal:1 Brake caliper removal2 Brake hose removal
3 Brake master cylinder removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removalREAR BRAKE REMOVAL
Hold the machine by placing the
suitable stand under the engine.
WARNING
Support the machine securely so there is nodanger of it falling over.
Rear wheel Refer to “FRONT WHEEL AND REAR
WHEEL” section.
Drain the brake fluid. Refer to “REMOVAL POINTS”.
1 Pad pin plug 1 Remove when loosening the pad pin.
2 Pad pin 1 Loosen when disassembling the caliper.
3 Brake caliper 1
4 Brake hose holder 2
5 Union bolt 2
6 Brake hose 1
7 Brake pedal 1
8 Reservoir tank 1
9 Reservoir hose 1
10Brake master cylinder
1
3
1
321
FRONT BRAKE AND REAR BRAKE

5 - 14
CHASFRONT BRAKE AND REAR BRAKE
EC5A3000
REMOVAL POINTS
Brake fluid
1. Remove:
[Front]
lBrake master cylinder cap 1
[Rear]
lBrake master cylinder guard 1
lReservoir tank cap 2
NOTE:
Do not remove the diaphragm.
Front
õRear
2. Connect the transparent hose 2 to the
bleed screw 1 and place a suitable con-
tainer under its end.
Front
õRear

õ
3. Loosen the bleed screw and drain the
brake fluid while pulling the lever in or
pushing down on the pedal.
ACHTUNG:CAUTION:
lDo not reuse the drained brake fluid.
lBrake fluid may erode painted surfaces or
plastic parts. Always clean up spilled
fluid immediately.
õ

Brake caliper piston
1. Remove:
lBrake caliper piston
Use compressed air and proceed care-
fully.
WARNING
lCover piston with rag and use extreme
caution when expelling piston from cylin-
der.
lNever attempt to pry out piston.
Front
õRear
Caliper piston removal steps:
lInsert a piece of rag into the brake caliper
to lock one brake caliper.
lCarefully force the piston out of the brake
caliper cylinder with compressed air.

õ

5 - 15
CHASFRONT BRAKE AND REAR BRAKE
Brake caliper piston seal kit
1. Remove:
lDust seal 1
lPiston seal 2
NOTE:
Remove the piston seals and dust seals by
pushing them with a finger.
ACHTUNG:CAUTION:
Never attempt to pry out piston seals and
dust seals.
WARNING
Replace the piston seals and dust seals
whenever a caliper is disassembled.
Front
õRear

õ
EC5A4000
INSPECTION
Brake master cylinder
1. Inspect:
lBrake master cylinder inner surface a
Wear/scratches ® Replace master cyl-
inder assembly.
Stains ® Clean.
WARNING
Use only new brake fluid.
Front
õRear
2. Inspect:
lDiaphragm 1
Crack/damage ® Replace.
Front
õRear
õ
õ

3. Inspect:
lBrake master cylinder piston 1
lBrake master cylinder cup 2
Wear/damage/score marks ® Replace
brake master cylinder kit.
Front
õRear
õ

5 - 16
CHAS
Brake caliper
1. Inspect:
lBrake caliper cylinder inner surface a
Wear/score marks ® Replace brake
caliper assembly.
Front
õRear
õ
2. Inspect:
lBrake caliper piston 1
Wear/score marks ® Replace brake
caliper piston assembly.
WARNING
Replace the piston seals and dust seals 2
whenever a caliper is disassembled.
EC534301
Brake hose
1. Inspect:
lBrake hose 1
Crack/damage ® Replace.
EC5A5000
ASSEMBLY AND INSTALLATION
WARNING
lAll internal parts should be cleaned in
new brake fluid only.
lInternal parts should be lubricated with
brake fluid when installed.
lReplace the piston seals and dust seals
whenever a caliper is disassembled.
Brake caliper piston
1. Clean:
lBrake caliper
lPiston seal
lDust seal
lBrake caliper piston
Clean them with brake fluid.
FRONT BRAKE AND REAR BRAKE

5 - 17
CHAS
2. Install:
lPiston seal 1
lDust seal 2
WARNING
Always use new piston seals and dust
seals.
NOTE:
Fit the piston seals and dust seals onto the slot
on brake caliper correctly.
Front
õRear

õ
3. Install:
lBrake caliper piston 1
NOTE:
Apply the brake fluid on the piston wall.
ACHTUNG:CAUTION:
lFor the front brake caliper, install the pis-
ton with its depressed side a facing the
brake caliper. For the rear brake caliper,
install the piston with its shallow
depressed side b facing the caliper.
lNever force to insert.
Front
õRear
Front brake caliper
1. Install:
lPad support 1
lBrake pad 2
lPad pin 3
NOTE:
lInstall the brake pads with their projections
a into the brake caliper recesses b.
lTemporarily tighten the pad pin at this point.

õ
FRONT BRAKE AND REAR BRAKE

5 - 18
CHASFRONT BRAKE AND REAR BRAKE
2. Install:
lCopper washer 1
lUnion bolt 2
WARNING
Always use new copper washers.
ACHTUNG:CAUTION:
Install the brake hose so that its pipe por-
tion a directs as show and lightly touches
the projection b on the brake caliper.
T R..30 Nm (3.0 m · kg, 22 ft · lb)
3. Install:
lBrake hose holder 1
lBrake caliper 2
lBolt (brake caliper) 3
NOTE:
Fit the brake hose holder cut a over the pro-
jection b on the front fork and clamp the brake
hose.
4. Tighten:
lPad pin 4
5. Install:
lPad pin plug 5
Rear brake caliper
1. Install:
lPad support 1
lBrake pad 2
lPad pin 3
NOTE:
lInstall the brake pads with their projections
a into the brake caliper recesses b.
lTemporarily tighten the pad pin at this point.
T R..23 Nm (2.3 m · kg, 17 ft · lb)
T R..18 Nm (1.8 m · kg, 13 ft · lb)
T R..3 Nm (0.3 m · kg, 2.2 ft · lb)

5 - 19
CHASFRONT BRAKE AND REAR BRAKE
2. Install:
lBrake disc cover 1
lBolt (brake disc cover) 2
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)
3. Install:
lCopper washer 1
lBrake hose 2
lUnion bolt 3
WARNING
Always use new copper washers.
ACHTUNG:CAUTION:
Install the brake hose to the brake caliper
with the paint a on the pipe facing the
brake caliper and with the pipe contacting
the brake caliper projection b.
T R..30 Nm (3.0 m · kg, 22 ft · lb)
4. Install:
lBrake caliper 1
lRear wheel 2
Refer to “FRONT WHEEL AND REAR
WHEEL” section.
5. Tighten:
lPad pin 3
6. Install:
lPad pin plug 4
T R..18 Nm (1.8 m · kg, 13 ft · lb)
T R..3 Nm (0.3 m · kg, 2.2 ft · lb)

5 - 20
CHASFRONT BRAKE AND REAR BRAKE
Brake master cylinder kit
1. Clean:
lBrake master cylinder
lBrake master cylinder kit
Clean them with brake fluid.
2. Install:
lBrake master cylinder cup (primary) 1
lBrake master cylinder cup (secondary)
2
To brake master cylinder piston 3.
NOTE:
Apply the brake fluid on the brake master cyl-
inder cup.
WARNING
After installing, cylinder cup should be
installed as shown direction. Wrong instal-
lation cause improper brake performance.
Front
õRear
õ

3. Install:
lSpring 1
To brake master cylinder piston 2.
NOTE:
Install the spring at the smaller dia. side.
Front
õRear