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 DiscClutch Lever Installation
Install the clutch lever so that the mating surface [A] of the
clutch lever clamp is aligned with the punch mark [B] of
the handlebar.
Tighten the upper clamp bolt first, and then the lower
clamp bolt.
Torque - Clutch Lever Clamp Bolts: 7.8 N·m (0.80 kgf·m, 69
in·lb)
There will be ...
System Components
1. KIBS ECU
With input from the front and rear wheel sensors and front
caliper hydraulic pressure, the KIBS ECU analyzes various
conditions on the motorcycle, and with additional information
from the FI ECU (engine speed, throttle position, gear
position, and clutch actuation) precisely control ...
Periodic Maintenance Chart
K : Should be serviced by an authorized Kawasaki dealer.
* : For higher odometer readings, repeat at the frequency interval established
here.
# : Service more frequently when operating in severe conditions: dusty, wet,
muddy,
high speed, or frequent starting/stopping.
(e): Emission Rel ...