brake YAMAHA YZ125LC 2003 Service Manual

5-13
CHASFRONT BRAKE AND REAR BRAKE
Extent of removal Order Part name Q’ty Remarks
MASTER CYLINDER DISASSEMBLY
1Master cylinder cap 1
2Diaphragm 1
3Master cylinder boot 1
4Circlip 1 Use a long nose circlip pliers.
5Plain washer 1
6Push rod 1
7Master cylinder kit 1
EC5A8300
MASTER CYLINDER DISASSEMBLY
AFront
BRear
Extent of removal:1Front master cylinder disassembly2Rear master cylinder disassembly
1
1
2
2
2 Nm (0.2 m•kg, 1.4 ft•lb)2 Nm (0.2 m•kg, 1.4 ft•lb)å
∫

5-14
CHASFRONT BRAKE AND REAR BRAKE
EC5A3000
REMOVAL POINTS
EC5A3101
Brake fluid
1. Remove:
[Front]
9Master cylinder cap 1
[Rear]
9Master cylinder cap 1
9Protector
NOTE:
Do not remove the diaphragm.
AFront
BRear
2. Connect the transparent hose 1to the
bleed screw 2and place a suitable contain-
er under its end.
AFront
BRear
3. Loosen the bleed screw and drain the brake
fluid while pulling the lever in or pushing
down on the pedal.
cC
9Do not reuse the drained brake fluid.
9Brake fluid may erode painted surfaces or
plastic parts. Always clean up spilled fluid
immediately.
EC533301
Caliper piston
1. Remove:
9Caliper piston
Use compressed air and proceed carefully.
w
9Cover piston with rag and use extreme cau-
tion when expelling piston from cylinder.
9Never attempt to pry out piston.
AFront
BRear
Caliper piston removal steps:
9Insert a piece of rag into the caliper to lock
one caliper.
9Carefully force the piston out of the caliper
cylinder with compressed air.

5-15
CHASFRONT BRAKE AND REAR BRAKE
EC533402
Piston seal kit
1. Remove:
9Dust seal 1
9Piston seal 2
NOTE:
Remove the piston seals and dust seals by
pushing them with a finger.
cC
Never attempt to pry out piston seals and
dust seals.
w
Replace the piston seals and dust seals
whenever a caliper is disassembled.
AFront
BRear
EC5A4000
INSPECTION
EC534112
Master cylinder
1. Inspect:
9Master cylinder inner surface a
Wear/ScratchesReplace master cylinder
assembly.
StainsClean.
w
Use only new brake fluid.
AFront
BRear
2. Inspect:
9Diaphragm 1
Crack/DamageReplace.
AFront
BRear
3. Inspect:
9Master cylinder piston 1
9Master cylinder cup 2
Wear/Damage/Score marksReplace master
cylinder kit.
AFront
BRear

5-16
CHASFRONT BRAKE AND REAR BRAKE
EC534214
Caliper
1. Inspect:
9Caliper cylinder inner surface a
Wear/Score marksReplace caliper as-
sembly.
AFront
BRear
2. Inspect:
9Caliper piston 1
Wear/Score marksReplace caliper piston
assembly.
w
Replace the piston seals and dust seals 2 2
whenever a caliper is disassembled.
EC534301
Brake hose
1. Inspect:
9Brake hose 1
Crack/DamageReplace.
EC5A5000
ASSEMBLY AND INSTALLATION
w
9All internal parts should be cleaned in
new brake fluid only.
9Internal parts should be lubricated with
brake fluid when installed.
9Replace the piston seals and dust seals
whenever a caliper is disassembled.
EC5A5801
Caliper piston
1. Clean:
9Caliper
9Piston seal
9Dust seal
9Caliper piston
Clean them with brake fluid.

5-17
CHASFRONT BRAKE AND REAR BRAKE
2. Install:
9Piston seal 1
9Dust seal 2
w
Always use new piston seals and dust
seals.
NOTE:
Fit the piston seals and dust seals onto the slot
on caliper correctly.
AFront
BRear
3. Install:
9Caliper piston 1
NOTE:
Apply the brake fluid on the piston wall.
cC
9Install the piston with its shallow
depressed side a a
facing the caliper.
9Never force to insert.
AFront
BRear
EC5A5700
Front caliper
1. Install:
9Pad support 1
9Brake pad 2
9Pad pin 3
NOTE:
9Install the brake pads with their projections
ainto the caliper recesses b.
9Temporarily tighten the pad pin at this point.

5-18
CHASFRONT BRAKE AND REAR BRAKE
3. Install:
9Brake hose holder 1
9Caliper 2
9Bolt (caliper) 3
NOTE:
Fit the brake hose holder cut aover the projec-
tion bon the front fork and clamp the brake
hose.
4. Tighten:
9Pad pin 4
5. Install:
9Pad pin plug 5
EC5A5121
Rear caliper
1. Install:
9Pad support 1
9Brake pad 2
9Pad pin 3
NOTE:
9Install the brake pads with their projections
ainto the caliper recesses b.
9Temporarily tighten the pad pin at this point.
2. Install:
9Copper washer 1
9Union bolt 2
w
Always use new copper washers.
cC
Install the brake hose so that its pipe por-
tion a a
directs as shown and lightly touch-
es the projection b b
on the caliper.
30 Nm (3.0 m•kg, 22 ft•lb)
23 Nm (2.3 m•kg, 17 ft•lb)
18 Nm (1.8 m•kg, 13 ft•lb)
3 Nm (0.3 m•kg, 2.2 ft•lb)

5-19
CHASFRONT BRAKE AND REAR BRAKE
2. Install:
9Disc cover 1
9Bolt (disc cover) 2
7 Nm (0.7 m•kg, 5.1 ft•lb)
3. Install:
9Caliper 1
9Rear wheel 2
Refer to “FRONT WHEEL AND REAR
WHEEL” section.
4. Tighten:
9Pad pin 3
5. Install:
9Pad pin plug 4
EC5A5220
Master cylinder kit
1. Clean:
9Master cylinder
9Master cylinder kit
Clean them with brake fluid.
2. Install:
9Master cylinder cup (primary) 1
9Master cylinder cup (secondary) 2
To master cylinder piston 3.
NOTE:
Apply the brake fluid on the master cylinder cup.
w
After installing, cylinder cup should be in-
stalled as shown direction. Wrong installa-
tion cause improper brake performance.
AFront
BRear
18 Nm (1.8 m•kg, 13 ft•lb)
3 Nm (0.3 m•kg, 2.2 ft•lb)

5-20
CHASFRONT BRAKE AND REAR BRAKE
3. Install:
9Spring 1
To master cylinder piston 2.
NOTE:
Install the spring at the smaller dia. side.
AFront
BRear
4. Install:
[Front]
9Master cylinder kit 1
9Plain washer 2
9Circlip 3
9Master cylinder boot 4
To master cylinder 5.
[Rear]
9Master cylinder kit 1
9Push rod 2
9Circlip 3
9Master cylinder boot 4
To master cylinder 5.
NOTE:
9Apply the brake fluid on the master cylinder
kit.
9Apply the lithium soap base grease on the tip
of the push rod.
9When installing the circlip, use a long nose
circlip pliers.
AFront
BRear
EC5A5310
Front master cylinder
1. Install:
9Master cylinder 1
9Master cylinder bracket 2
9Bolt (master cylinder bracket) 3
NOTE:
9Install the bracket so that the arrow mark a
face upward.
9First tighten the bolts on the upper side of the
master cylinder bracket, and then tighten the
bolts on the lower side.
9 Nm (0.9 m•kg, 6.5 ft•lb)

5-21
CHASFRONT BRAKE AND REAR BRAKE
2. Install:
9Brake lever 1
9Bolt (brake lever) 2
9Nut (brake lever) 3
NOTE:
Apply the lithium soap base grease on the
brake lever sliding surface, bolt and contacting
surface of the master cylinder piston.
6 Nm (0.6 m•kg, 4.3 ft•lb)
6 Nm (0.6 m•kg, 4.3 ft•lb)
EC5A5401
Rear master cylinder
1. Install:
9Copper washer 1
9Brake hose 2
9Union bolt 3
w
Always use new copper washers.
cC
Install the brake hose so that its pipe por-
tion
a adirects as shown and lightly touch-
es the projection
b bon the master cylinder.
30 Nm (3.0 m•kg, 22 ft•lb)
2. Install:
9Master cylinder 1
9Bolt (master cylinder) 2
10 Nm (1.0 m•kg, 7.2 ft•lb)

3. Install:
9Spring 1
9Brake pedal 2
9O-ring 3
9Bolt (brake pedal) 4
9Clip 5
NOTE:
9Apply the lithium soap base grease on the
bolt, O-ring and brake pedal bracket.
9Install the clip with its stopper portion afac-
ing inward.
5-22
CHASFRONT BRAKE AND REAR BRAKE
26 Nm (2.6 m•kg, 19 ft•lb)
EC5A5911
Front brake hose
1. Install:
9Brake hose 1
To brake hose holder 2.
NOTE:
Before tightening the bolt (brake hose holder),
align the top aof the brake hose neck with the
brake hose holder bottom b. Then pass the
brake hose in front of the axle boss cand fit it
into the hose groove dso that the brake hose
does not contact the nut (wheel axle).
2. Install:
9Hose cover 1
9Plain washer 2
9Bolt [hose cover (M8)] 3
9Bolt [hose cover (M6)] 4
10 Nm (1.0 m•kg, 7.2 ft•lb)
16 Nm (1.6 m•kg, 11 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
4. Install:
9Pin 1
9Plain washer 2
9Cotter pin 3
NOTE:
After installing, check the brake pedal height.
Refer to “REAR BRAKE ADJUSTMENT” section
in the CHAPTER 3.