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 DiscExploded View
25. “1T” marked side faces up.
26. “T2” marked side faces up.
27. Hollow mark faces exhaust side.
G: Apply grease.
L: Apply a non-permanent locking agent.
LG: Apply liquid gasket.
M: Apply molybdenum disulfide grease.
MO: Apply molybdenum disulfide oil solution.
...
Front Wheel Rotation Sensor Wiring Inspection (Service Code b 43)
Disconnect the front wheel rotation sensor lead connector
[A] (see Front Wheel Rotation Sensor Removal in the
Brakes chapter).
Disconnect the KIBS hydraulic unit lead connector (see
KIBS Hydraulic Unit Removal in the Brakes chapter).
Check the wiring continuity of the W lead and ...
Technical Information-Power Mode
The rider can choose from three engine power modes to suit their preferences
and road conditions.
The FI ECU controls the engine power by adjusting fuel injection, air intake,
and ignition timing. It
enables three-mode selection: Full Power (Mode F), Middle Power (Mode M), and
Low Power (M ...