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 DiscIdle Speed Control Valve Actuator Installation
Replace the O-ring [A] with a new one.
Apply engine oil to the new O-ring.
Install the idle speed control valve [A] as shown in the
figure.
10° [B]
Tighten:
Torque - Idle Speed Control Valve Actuator Retainer
Screws: 2.06 N·m (0.21 kgf·m, 18 in·lb)
Install th ...
KIBS Troubleshooting Outline
When an abnormality in the system occurs, the ABS indicator
light (LED) and KIBS indicator light (LED) light up and
the KIBS warning symbol are displayed on the LCD (Liquid
Crystal Display) to alert the rider. In addition, the nature of
the fault is stored in the memory of the KIBS hydraulic uni ...
ECU Identification
Most countries have their own regulations, so each ECU
has different characteristic. So, do not confuse ECU with
each other and use only the ECU for your model. Otherwise,
the motorcycle can not clear the regulation.
ECU Identification
ZX1000JB/KB
ZX1000JC /KC
...