2006-2009 Honda TRX250EX/TRX250X Service Manual, Page 154Get this manual
CYLINDERPISTON Check th top of the cylinder for warpage ith straight edge and feeler gauge across the stud holesSERVICE LIMIT: 0.10 mm (0.004 in)
PISTONPISTON RING
Inspect the piston rings for smooth movement by rotating he 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 LIMIT: TopSecond0.09 mm (0.004 in)