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 DiscSteering Play Inspection
Remove the lower fairings (see Lower Fairing Removal in
the Frame chapter).
Raise the front wheel off the ground with the jack.
Special Tools - Jack: 57001-1238
Jack Attachment: 57001-1608
With the front wheel pointing straight ahead, alternately
tap each end of the handlebar. The f ...
KIBS Hydraulic Unit Terminal Names
1. Ground: BK
2. CAN Communication Line (High): GY/BL
3. Front Wheel Rotation Sensor Signal Input: Y
4. Power Supply: BR/W
5. KIBS Kawasaki Self-Daignosis System Terminal: P
6. Front and Rear Brake Light Switch Signal: BL/R
7. Unused
8. Front Wheel Rotation Sensor Signal Output: G/Y
9. P ...
Inquiries to Rider
Each rider reacts to problems in different ways, so it is important to
confirm what kind of condition
the rider is dissatisfied with.
Try to find out exactly what problem occurs under exactly what
conditions by asking the rider; knowing
this information may help you reproduce the prob ...