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 DiscThrottle Body Assy Installation
Apply a thin coat of grease to the throttle cable lower ends.
Fit the accelerator cable end [A] and the decelerator cable
end [B] into the throttle pulley.
Install the clamp [C] securely.
Install the throttle body assy holder clamp bolt heads [A]
outside as shown in the figure.
...
Meter Unit Circuit (ZX1000K Model)
1. Ignition Switch
2. Joint Connector F
3. Stop Watch Button
4. Oil Pressure Switch
5. Crankshaft Sensor
6. Water Temperature Sensor
7. Gear Position Switch
8. Intake Air Temperature Sensor
9. ESD ECU (ZX1000JD/KD)
10. ECU
11. Rear Wheel Rotation Sensor
12. Frame Ground 1
13. Engine ...
Oxygen Sensor - not activated (Service Code 33, Equipped Models)
Oxygen Sensor Removal/Installation
Refer to the Oxygen Sensor Removal/Installation
(Equipped Models) in the Electrical System chapter.
Oxygen Sensor Inspection
Remove:
Fuel Tank (see Fuel Tank Removal in the Fuel System
(DFI) chapter)
Oxygen Sensor Lead Connector [A]
Connect t ...