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 DiscArmature Inspection
Using the × 1 Ω hand tester range, measure the resistance
between any two commutator segments [A].
Special Tool - Hand Tester: 57001-1394
If there is a high resistance or no reading (∞) between any
two segments, a winding is open and the starter motor
must be replaced.
...
IC Igniter Inspection
The IC igniter is built in the ECU [A].
Refer to the following items.
Interlock Operation Inspection (see Interlock Operation
Inspection)
Ignition System Troubleshooting (see Ignition System
section)
ECU Power Supply Inspection (see ECU Power Supply
Inspection in the Fuel System (D ...
Spring Plate Free Play Measurement
Insufficient clutch free play will cause the engine braking
effect to be more sudden, resulting in rear wheel hop. On
the other hand, if the free play is excessive, the clutch lever
may feel “spongy” or pulsate when pulled.
Hold an extra drive shaft in a vise and install the following
c ...