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 DiscTire Repair
Currently two types of repair for tubeless tires have come
into wide use. One type is called a temporary (external) repair
which can be carried out without removing the tire from
the rim, and the other type is called permanent (internal)
repair which requires tire removal. It is generally unders ...
Meter Unit Inspection
Remove the meter unit (see Meter Unit Removal).
[1] Battery (+)
[2] Fuel Reserve Switch
[3] Ground (–)
[4] Unused
[5] Right Turn Signal Indicator Light (LED) (+)
[6] Left Turn Signal Indicator Light (LED) (+)
[7] High Beam Indicator Light (LED) (+)
[8] Neutral Indicator Light (LED) (в ...
Self-Diagnosis Procedures
NOTE
Use a fully charged battery when conducting
self-diagnosis. Otherwise, the light (LED) and symbol
do not light or blink.
Turn the ignition switch to ON.
When a problem occurs with DFI system and ignition system,
the warning indicator light (LED) [A] goes on and
FI warning symbol ...