2004-2005 Honda TRX450R Factory Sevice Manual, Page 167Get this manual
CYLINDERPISTON Check th top of the cylinder for wa rpage with straight edge and feeler gauge across the stud holesSERVICE LIMIT; 0.05 mm (0.002 in)
PISTONPISTON RING
Insp ect th piston rings for smooth movement by rotating the themThe rings should be able mov in their grooves without catchingPush the ri ng until the outer surface of the piston ring is nearly flush with the pis ton and measure he ring -to-ring groove clearanceSERVICE LIMITS;
015 mm (0.0045 in)
Second: 0.075 mm (0.0030 in)
Insert the piston ring nt the bottom of the cylinder squarely using the piston crown