If the measurement is under service limit, replace the piston.

Piston Diameter
Standard: 75.959
75.974 mm
(2.9905
2.9911 in.)
Service Limit: 75.81 mm (2.985 in.)
Cylinder (Upper Crankcase) Wear Inspection
Piston Ring, Piston Ring Groove Wear InspectionRear Sprocket Removal
Remove the rear wheel (see Rear Wheel Removal in the
Wheels/Tires chapter).
NOTICE
Do not lay the wheel on the ground with the disc
facing down. This can damage or warp the disc.
Place blocks under the wheel so that the disc does
not touch the ground.
Remove:
Rear Sprocket Nu ...
Oil Level Inspection
If the oil has just been changed, start
the engine and run it for severalminutes
at idle speed. This fills the oil
filter with oil. Stop the engine, then
wait several minutes until the oil settles.
NOTICE
Racing the engine before the oil
reaches every part can cause engine
seizure.
...
Idle Speed
The idle speed inspection should be
performed in accordance with the Periodic
Maintenance Chart.
This motorcycle is equipped with the
Idle Speed Control valve. If the idle
speed is disturbed, inspection of the
idle speed control should be done by
an authorized Kawasaki dealer.
NOTE
While ...