Checking The Brake Operation; Bleeding The Hydraulic Brake System - Yamaha YZ450FN 2022 Owner's Service Manual

Loose connection  Tighten the holder bolt.
3. Hold the vehicle upright and apply the rear
brake several times.
4. Check:
• Brake hose
Brake fluid leakage  Replace the damaged
hose.
Refer to "REAR BRAKE" on page 4-24.
EAM30499

CHECKING THE BRAKE OPERATION

1. Check:
• Brake operation
Brake not working properly  Check the
brake system.
Refer to "FRONT BRAKE" on page 4-13 and
"REAR BRAKE" on page 4-24.
TIP
Drive on the dry road, operate the front and rear
brakes separately and check to see if the brakes
are operating properly.
EAM30477
BLEEDING THE HYDRAULIC BRAKE
SYSTEM
EWA19140
WARNING
Bleed the brake system whenever:
• The system is disassembled.
• A brake hose is loosened, disconnected, or
replaced.
• The brake fluid level is very low.
• Brake operation is faulty.
1. Remove:
• Brake master cylinder cap
• Reservoir diaphragm
• Reservoir float (front brake)
• Protector (rear brake)
TIP
• Be careful not to spill any brake fluid or allow
the reservoir to overflow.
• Make sure that there is enough brake fluid be-
fore applying the brake. Ignoring this precau-
tion could allow air to enter the brake system,
considerably lengthening the bleeding proce-
dure.
• If bleeding is difficult, it may be necessary to let
the brake fluid settle for a few hours. Repeat
the bleeding procedure when the tiny bubbles
in the hose have disappeared.
2. Bleed the brake system.
a. Fill the reservoir to the proper level with
the recommended brake fluid.
b. Install the reservoir diaphragm.
c. Connect the plastic hose "1" to the bleed
screw "2" securely, and place a container
under the end of the plastic hose.
2
2 2
A. Front
B. Rear
d. Slowly apply the brake several times.
e. Fully pull the brake lever or fully press
down the brake pedal and hold it in posi-
tion.
f. Loosen the bleed screw.
TIP
Loosening the bleed screw will release the pres-
sure in the brake caliper and cause the brake le-
ver to contact the throttle grip or the brake pedal
to fully extend.
g. Tighten the bleed screw and then release
the brake lever or brake pedal.
h. Repeat steps (d) to (g) until all of the air
bubbles have disappeared from the brake
fluid in the plastic hose.
TIP
During the procedure, keep adding brake fluid to
the reservoir.
ECA24320
NOTICE
• Wipe off any brake fluid on the brake discs,
tires, wheels, etc.
• Brake fluid may erode painted surfaces or
plastic parts. Always clean up spilled fluid
3-25
CHASSIS
1
1