Use the micrometer to measure at several points around the ring.
Piston Ring Thickness Standard:
Top [A] 0.77 
0.79 mm (0.0303
0.0311 in.)
Second [B] 0.78 
0.79 mm
(0.0307 
0.0311 in.)
Service Limit:
Top 0.70 mm (0.0276 in.)
Second 0.71 mm (0.0280 in.)
If any of the measurements is less than the service limit on either of the rings, replace all the rings.
NOTE
When using new rings in a used piston, check for uneven groove wear. The rings should fit perfectly parallel to the groove sides. If not, replace the piston.
Piston Ring Groove Width Inspection
Piston Ring End Gap InspectionWheel Bearing Damage Inspection
Raise the front wheel off the ground with the jack (see
Front Wheel Removal in the Wheels/Tires chapter).
Special Tools - Jack: 57001-1238
Jack Attachment: 57001-1608
Turn the handlebar all the way to the right or left.
Inspect the roughness of the front wheel bearing by moving
[A] ...
Camshaft Runout Inspection
Remove the camshafts (see Camshaft Removal).
Set the camshaft in a camshaft alignment jig or on V
blocks.
Measure the runout with a dial gauge at the specified
place as shown in the figure.
If the runout exceeds the service limit, replace the
camshaft.
Camshaft Runout
Standard: TIR ...
Thermostat Installation
Replace the O-rings [A] with new ones, and apply grease
to them.
Assemble:
O-rings
Thermostat Housing [B]
Thermostat [C]
Thermostat Cap [D]
Install the thermostat [A] in the housing so that the air
bleeder hole [B] is on top.
Tighten:
Torque - Thermostat Cap Bolts: 5.9 N ...