2005-2009 Honda TRX400EX/TRX400X Service Manual, Page 147Get this manual
CYLINDERPISTON Check the top of the cylinder for warpage with straight edge and feeler gauge across the stud holesSERVICE LIMIT: 0.10 mm (0.004 in l
PISTON PISTON RING Inspect the piston rings for smooth movement by rolating the them The rin gs should be ab le to move in th eir grooves without catching Push the ring until the outer surface of the piston ring is near ly flush with the piston and measu re the ring -toring groove clearanceSERVICE LIMITS: Top0.14 mm (0.006 in) Second: 0.12 mm (0.005 in)