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 InspectionBrake Line Bleeding
The brake fluid has a very low compression coefficient so
that almost all the movement of the brake lever or pedal
is transmitted directly to the caliper for braking action. Air,
however, is easily compressed. When air enters the brake
lines, brake lever or pedal movement will be partially used
...
Starter Motor Installation
NOTICE
Do not tap the starter motor shaft or body. Tapping
the shaft or body could damage the motor.
Clean the starter motor legs [A] and crankcase where the
starter motor is ground.
Replace the O-ring [A] with a new one.
Apply grease to the new O-ring.
Tighten:
Torque - Starter ...
Idle Speed Inspection
Start the engine and warm it up thoroughly.
With the engine idling, turn the handlebar to both sides
[A].
If handlebar movement changes the idle speed, the
throttle cables may be improperly adjusted or incorrectly
routed, or damaged. Be sure to correct any of these
conditions before rid ...