Brake Disk Wear - Derbi GP1 50 cc Workshop Manual

Brake disk wear

- Measure the thickness of the disks (A) at the point where
they are most worn.
- If the disk is more worn than specified in the service limit,
renew it.
Measurement area (B).
Standard brake disk thickness:
3.3 ÷ 3.6 mm.
Service limit:
3.1 mm.
Brake disk distortion
- Raise the motorcycle on the jack so that the tyre is clear of
the ground.
- Place a dial calibrator against the disk (A) as shown, and
measure the disk's deviation from centre as the tyre is turned
(B) by hand.
- If the deviation from centre exceeds the service limit, renew
the disk.
Disk deviation from centre:
Standard:
Inferior a 0,15 mm
Service limit:
0,3 mm
Bleeding the brake system pipe
The brake fluid has a very low compression coefficient, with
the result that almost all the movements of the brake lever
are transmitted directly to the calliper for braking. Air howe-
ver compresses easily. When air enters the brake system pi-
pes, the movement of the brake lever is partially used up in
compressing the air. This causes the pedal to feel spongy and
leads to a loss of braking power.
WARNING
BE SURE TO BLEED AIR OUT OF THE BRAKE SYSTEM WHEN
THE BRAKE LEVER FEELS SPONGY AFTER CHANGING THE
BRAKE FLUID OR WHEN THE BRAKE SYSTEM PIPE HAS BEEN
LOOSENED FOR ANY REASON.
Remove:
Reservoir cap (threaded)
- Fill the reservoir with new brake fluid up to the top reservoir
line.
- With the cap removed, pump the brake slowly several times
until no more bubbles rise up through the fluid.
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