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 DiscParking
WARNINGOperating or parking the vehicle
near flammable materials can
cause a fire, and can result in
property damage or severe personal
injury.
Do not idle or park your vehicle
in an area where tall or dry vegetation,
or other flammable materials
could come into cont ...
Lights and Switches Operation Inspection
First Step
Set the gear position in the neutral position.
Turn the ignition switch to ON.
The following lights should go on according to below table.
If the following light does not go on, inspect the meter
unit (see Meter Unit Inspection in the Electrical System
chapter).
...
CAN Communication (Transmission)/CAN Bus OFF Monitor Inspection (Service Code
b 57) CAN Communication (Reception) Monitor Inspection (Service Code b 58)
Remove:
Seat (see Seat Removal in the Frame chapter)
Immobilizer (Equipped Models)/Kawasaki Diagnostic
System Connector Cap [A]
Measure the CAN communication line resistance.
Immobilizer (Equipped Models)/Kawasaki Diagnostic
System Connector [A]
GY/BL Terminal [B]
LB Ter ...