Yamaha YZ450F 2021 - Removing the Rear Brake Master Cylinder; Checking the Rear Brake Master Cylinder; Assembling the Rear Brake Master Cylinder

REAR BRAKE
4-32
6. Check:
• Brake fluid level
The minimum level mark or below  Add.
Refer to “CHECKING THE BRAKE FLUID
LEVEL” on page 3-24.
7. Check:
• Brake pedal operation
A softy or spongy feeling  Bleed the brake
system.
Refer to “BLEEDING THE HYDRAULIC
BRAKE SYSTEM” on page 3-25.
EAM30048
REMOVING THE REAR BRAKE MASTER
CYLINDER
TIP
Before removing the rear brake master cylinder,
drain the brake fluid from the entire brake sys-
tem.
1. Remove:
• Union bolt
• Copper washer
• Brake hose
TIP
To drain any remaining brake fluid, place a con-
tainer under the master cylinder and the end of
the brake hose.
EAM30049
CHECKING THE REAR BRAKE MASTER
CYLINDER
1. Check:
• Brake master cylinder “1”
Damage/scratches/wear  Replace.
• Brake fluid delivery passages “2”
(brake master cylinder body)
Obstruction  Blow out with compressed air.
2. Check:
• Brake master cylinder kit
Damage/wear  Replace.
3. Check:
• Master cylinder reservoir cap
Crack/damage  Replace.
• Brake master cylinder reservoir diaphragm
holder
• Brake master cylinder reservoir diaphragm
Crack/damage  Replace.
4. Check:
• Brake hose
Cracks/damage/wear  Replace.
EAM30050
ASSEMBLING THE REAR BRAKE MASTER
CYLINDER
WARNING
EWA13520
• Before installation, all internal brake com-
ponents should be cleaned and lubricated
with clean or new brake fluid.
• Never use solvents on internal brake com-
ponents.
1. Wash the brake master cylinder and the
brake master cylinder kit with brake fluid.
2. Install:
• Primary cylinder cup “1”
• Secondary cylinder cup “2”
Install to the brake master cylinder piston “3”.
WARNING
EWA19300
Apply brake fluid to the cylinder cups and in-
stall them as shown. Wrong orientation in in-
stallation causes poor braking performance.
1
2
Specified brake fluid
DOT 4
2
3
1
2
3
1