Yamaha WR450FB 2012 Owner's Service Manual page 108

EAS1DX3099
BLEEDING THE HYDRAULIC BRAKE SYS-
TEM
EWA13100
AwARNING
Bleed· the hydraulic brake system whenev-
er:
• 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 reservoir cap
TIP _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
• Be careful not to spill any brake fluid or allow
the brake master cylinder reservoir or brake
fluid reservoir to overflow.
• When bleeding the hydraulic brake system,
make sure there is always enough brake fluid
before applying the brake. Ignoring this pre-
caution could allow air to enter the hydraulic
brake system, considerably lengthening the
bleeding procedure.
• If bleeding is difficult, it may be necessary to
let the brake fluid settle for a few hours. Re-
peat the bleeding procedure when the tiny
bubbles in the hose have disappeared.
2. Bleed:
• Hydraulic brake system
TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT
a. Fill the brake fluid reservoir to the proper lev-
el with the recommended brake fluid.
b. Install the diaphragm (brake master cylinder
. reservoir or brake fluid reservoir).
c. Connect a clear plastic hose "1" tightly to the
bleed screw "2", and place an oil pan under
the vinyl hose end on one side.
PERIODIC MAINTENANCE
A. Front
B. Rear
d. Place the other end of the hose into a con-
tainer.
e. Slowly apply the brake several times.
f. Fully pull the brake lever or fully press down
the brake pedal and hold it in position.
g. Loosen the bleed screw.
TIP _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Loosening the bleed screw will release the
pressure and cause the brake lever to contact
the throttle grip or the brake pedal to fully ex-
tend.
h. Tighten the bleed screw and then release
the brake lever or brake pedal.
i.
Repeat steps (e) to (h) until all of the air bub-
bles have disappeared from the brake fluid
in the plastic hose.
j. Tighten the bleed screw to specification.
3-20
~ , , , , .
Bleed screw
~~
6 Nm (0.6 m·kgf, 4.3 ft-lbf)
k. Fill the brake fluid reservoir to the proper lev-
el with the recommended brake fluid.
Refer to "CHECKING THE BRAKE FLUID
LEVEL" on page 3-17.
EWA13110
j\WARNING
After bleeding the hydraulic brake system,
check the brake operation.