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 DiscSwingarm Installation
Visually inspect the chain guide [A].
Replace the chain guide if it shows any signs of abnormal
wear or damage.
Apply a non-permanent locking agent to the threads of
the chain guide bolt [B].
Apply plenty of grease to the lip of the oil seals [A].
Be sure to install the oil seals ...
Exhaust Butterfly Valve Actuator Sensor Resistance Inspection
Turn the ignition switch to OFF.
Disconnect the exhaust butterfly valve actuator sensor
connector (3 pins connector) [A] (see Exhaust Butterfly
Valve Actuator Sensor Input Voltage Inspection).
Connect a digital meter [B] to the exhaust butterfly valve
actuator sensor connector.
Measur ...
Camshaft Runout Inspection
Remove the camshafts (see Camshaft Removal).
Set the camshaft in a camshaft alignment jig or on V
blocks.
Measure the runout with a dial gauge at the specified
place as shown in the figure.
If the runout exceeds the service limit, replace the
camshaft.
Camshaft Runout
Standard: TIR ...