If a master cylinder or piston shows any damage, replace them.

If a cup is worn, damaged softened (rotted), or swollen, the piston assembly should be replaced to renew the cups.
If fluid leakage is noted at the brake lever, the piston assembly should be replaced to renew the cups.
If they are damaged, replace them.
If the springs are damaged, replace them.
If the relief port becomes plugged, the brake pads will drag on the disc. Blow the ports clean with compressed air.
Front Master Cylinder [I] Rear Master Cylinder [J]

Rear Master Cylinder Installation
Brake DiscPiston Wear Inspection
Measure the outside diameter [A] of each piston 5 mm
(0.20 in.) [B] up from the bottom of the piston at a right
angle to the direction of the piston pin.
If the measurement is under service limit, replace the piston.
Piston Diameter
Standard: 75.959 75.974 mm
(2.9905 2.9911 in.)
...
Front Wheel Rotation Sensor Signal Abnormal (Service Code b 42)
Measure the air gap between the front wheel rotation sensor
and sensor rotor.
Thickness Gauge [A]
Air Gap
Standard: 0.4 1.6 mm (0.02
0.06 in.)
If the measurement is not the standard, check each part
for deformation and looseness and correct accordingly.
If the measurement is t ...
Rear Turn Signal Light Bulb Replacement
Remove the upper seat cover (see Seat Cover Removal
in the Frame chapter).
Disconnect the tail/brake light connector [A].
Turn the socket [A] counterclockwise and remove the
socket together with the bulb.
Push and turn the turn signal light bulb [A] counterclockwise
an ...