Introduction; Checking The Rear Brake Disc - Yamaha YZ450FX 2019 Owner's Service Manual

EAM30040

INTRODUCTION

EWA19260
WARNING
If you need to disassemble the disc brake
components, observe the following precau-
tions.
• Never disassemble the brake components
unless absolutely necessary.
• If there is any problem with connections on
the hydraulic brake system, perform the
following jobs. Disassemble the brake sys-
tem, drain the brake fluid, and clean it. After
that, add a suitable amount of brake fluid.
Then, bleed it after reassembly.
• Use only brake fluid for washing internal
brake components.
• Use new brake fluid for cleaning the brake
components.
• Immediately wipe off the spilled brake fluid
to avoid damage to painted surfaces or
plastic parts.
• Handle brake fluid with special care not to
let it enter your eyes so that you may not
lost your eyesight.
• FIRST AID FOR BRAKE FLUID ENTERING
THE EYES:
• Flush with water for 15 minutes and get im-
mediate medical attention.
EAM30041

CHECKING THE REAR BRAKE DISC

1. Remove:
• Rear wheel
Refer to "REAR WHEEL" on page 4-9.
2. Check:
• Brake disc
Damage/galling  Replace.
3. Measure:
• Brake disc thickness
Measure the brake disc thickness at a few dif-
ferent locations.
Out of specification  Replace.
Refer to "CHECKING THE FRONT BRAKE
DISC" on page 4-17.
Brake disc thickness limit
3.5 mm (0.14 in)
4. Measure:
• Brake disc deflection
Out of specification  Correct the brake disc
deflection or replace the brake disc.
Brake disc runout limit (as mea-
sured on wheel)
0.15 mm (0.0059 in)
5. Adjust:
• Brake disc deflection
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Remove the brake disc.
b. Turn the mounted position of the brake disc
by one bolt hole.
c. Install the brake disc.
TIP
Tighten the brake disc bolts in stages and in a
crisscross pattern.
Brake disc bolt
12 N·m (1.2 kgf·m, 8.9 lb·ft)
LOCTITE®
d. Measure the brake disc deflection.
e. If out of specification, repeat the adjustment
steps until the brake disc deflection is within
specification.
f. If the brake disc deflection cannot be brought
within specification, replace the brake disc.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
6. Install:
• Rear wheel
Refer to "REAR WHEEL" on page 4-9.
4-27
REAR BRAKE