2006 Honda TRX680 Rincon Factory Service Manual, Page 232Get this manual
CYLINDERPISTON Check the top of the cylinder for warpage with straight edge and feeler gauge across the stud holesSERVICE LIMIT: 0.05 mm (0.002 in)
PISTONPISTON RING
Inspect the piston rings for smooth movement by rotating the themThe rings should be able to move in their grooves without catchingPush the ring until the outer surface of the piston ring is nearly flush with the piston and measure the ring-to-ring groove clearanceSERVICE LIMITS: Top: 0.095 mm (0.0037 in) Second: 0.075 mm (0.0030 in)