1986-1989 Honda TRX250 FourTrax 250R Service Manual, Page 65Get this manual
CYLINDER HEADCYLINDERPISTON Remove the gasket material rom the mating surface of the cylinderCheck the cylinder and piston for wear or damageClean carbon deposits from the exhaust port area CAUTION
Do not damage the cylinder boreNOTE
Under rac ing conditionsthe piston and rings should be replaced after 30 hours of running And the piston pin and connecti ng rod sma ll end bearing rep laced after 30 hours of running
Inspect the cylinder walls or scratches and wearMeasure and record the cylinder I.Dat three levels in both an and axisTake the maximum reading to determine the cylinder wearSERVICE LIMIT: (I.Dcode): 66.07 mm (2.6012 inl (1.0code): 66.06 mm (2.6008 in) Calculate the piston-to-cylinder clearanceTake the max imum reading to determine the clearanceSERVICE LIMIT: 0.14 mm 0.006 in) Ca lculate the cyli nder for taper at three levels in and YaxisTake the maximum read ing to determ ine the taper SERVICE LIMIT: .03 mm 0.001 in) Calculate the cylinder for out-of-round at three levels in and axisTake the maximum reading to determine the outof-roundSERVICE LIMIT: 0.03 mm (0.001 in) The cy linder must be rebored and oversize piston fitted if the service limits are exceededThe following oversize pistons are available: 0.25 mm (0.01 in) and 0.5 mm (0 .02 in) The cyl inder must be reba red so that the clearance to an oversize piston is 0.0600.080 mm (0.0024-0 .0031 in)Measu re and reco rd the piston 0.090 to he piston pin boreSERVICE LIMIT: (0 .0code): 65 .90 mm (2.5945 in) (0 .0 code)65.89 mm (2.5941 in) Compare this measurement against the service limit and calcula piston-to -cy linder clearanceMeasure the piston pin bore 1.0SERVICE LIMIT: 18.03 mm (0.710 in) Check the piston pin or wear and excessive discoloration Measure the piston pin .0SERVICE LIMIT: 17 .98 mm (0.708 in) Calculate he piston pin-to-piston clearanceSERVLlCE LIMIT: 0.03 mm 0.001 in)