Introduction; Checking The Front Brake Disc - Yamaha YZ 2020 Series Owner's Service Manual

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INTRODUCTION

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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 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.
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CHECKING THE FRONT BRAKE DISC

1. Check:
• Front brake disc
Damage/galling  Replace.
2. Measure:
• Brake disc thickness
Measure the brake disc thickness at a few dif-
ferent locations.
Out of specification  Replace.
Brake disc thickness limit
2.5 mm (0.10 in)
3. Measure:
• Brake disc runout
Out of specification  Correct the brake disc
runout or replace the brake disc.
Brake disc runout limit (as mea-
sured on wheel)
0.15 mm (0.0059 in)
a. Place the vehicle on a maintenance stand
so that the front wheel is elevated.
b. Remove the brake caliper.
c. Hold the dial gauge at a right angle against
the brake disc surface.
d. Measure the runout 1.5 mm (0.06 in)
above the brake disc edge.
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4. Adjust:
• Brake disc runout
a. Remove the front wheel.
Refer to "FRONT WHEEL" on page 4-5.
b. Remove the brake disc.
c. Rotate the brake disc by one bolt hole.
d. Install the brake disc.
Front brake disc bolt
12 N·m (1.2 kgf·m, 8.9 lb·ft)
LOCTITE®
TIP
Tighten the brake disc bolts in stages and in a
crisscross pattern.
e. Measure the brake disc runout.
f. If out of specification, repeat the adjust-
4-17
FRONT BRAKE
LT