Use a vernier caliper at several points around the piston.
Piston Ring Groove Width Standard:
Top [A] 0.82 
0.84 mm (0.0323
0.0331 in.)
Second [B] 0.82 
0.84 mm
(0.0323 
0.0331 in.)
Service Limit:
0.92 mm (0.036 in.)
Second 0.92 mm (0.036 in.)
If the width of any of the two grooves is wider than the service limit at any point, replace the piston.
Piston Ring, Piston Ring Groove Wear Inspection
Piston Ring Thickness InspectionSpark Plug Condition Inspection
Remove the spark plugs (see Spark Plug Replacement in
the Periodic Maintenance chapter).
Visually inspect the spark plugs.
If the spark plug center electrode [A] and/or side electrode
[B] are corroded or damaged, or if the insulator [C]
is cracked, replace the plug.
If the spark plug is ...
Upper Crankcase Assembly
When installing the breather plate, replace the gasket [A]
with a new one.
Apply a non-permanent locking agent to the threads of
the bolts [A] and tighten them.
Torque - Breather Plate Bolts: 9.8 N·m (1.0 kgf·m, 87 in·lb)
Install the fitting [A] until it is bottomed ...
Spring Plate Free Play Adjustment
NOTE
The free play adjustment is performed by replacing the
steel plate(s).
Measure the clutch spring plate free play (see Clutch
Spring Plate Free Play Measurement), and then replace
the steel plate(s) which brings the free play within the
usable range.
Spring Plate Free Play
Usable ...