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 DiscOutline
When a problem occurs with DFI system, the warning indicator
light (LED) [A] and FI warning symbol [B] goes on
to alert the rider. In addition, the condition of the problem is
stored in the memory of the ECU. For models equipped with
an immobilizer system, the warning indicator light (LED)
and ...
Lubrication
Lubrication is necessary after riding
through rain or on wet roads, or any
time that the chain appears dry.
Use a lubricant for sealed chains to
prevent deterioration of chain seals. If
the chain is especially dirty, clean it
using a cleaner for sealed chains following
the instructions suppli ...
Operational Cautions
1. Do not put two keys of any immobilizer system on the same key ring.
2. Do not submerge any key in water.
3. Do not expose any key to excessively high temperature.
4. Do not place any key close to magnet.
5. Do not place a heavy item on any key.
6. Do not grind any key or alter its ...