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 InspectionStarter Motor Disassembly
Remove the starter motor (see Starter Motor Removal).
Take off the starter motor through bolts [A] and remove
the both end covers [B].
Pull out the armature [A] out of the yoke [B].
NOTE
Do not remove the circlip [C] from the shaft.
Remove the starter motor terminal lock ...
Special Tools and Sealant
Oil Pressure Gauge, 5 kgf/cm²:
57001-125
Hand Tester:
57001-1394
Needle Adapter Set:
57001-1457
Extension Tube:
57001-1578
Fuel Pressure Gauge Adapter:
57001-1593
Fuel Hose:
57001-1607
Measuring Adapter:
57001-1700
Liquid Gasket, TB1211:
56019-120
...
Piston Removal
Remove:
Crankshaft (see Crankshaft Removal)
Remove the piston together with the connecting rod to the
cylinder head side.
NOTICE
Discard the connecting rod bolts and nuts. To prevent
damage to the crankpin surfaces, do not allow
the connecting rod bolts to bump against the
crankpins. ...