1985-1986 Honda ATC250R Shop Manual, Page 72Get this manual
5SERVICE INFORMATION TROUBLESHOOTING CYLINDER HEAD CYLINDERPISTON
CYLINDER HEAD CYLINDERPISTON
SERVICE INFORMATION
GENERAL
All cylinder head, cylinder and piston maintenance and inspection can be done with the engine installedBefore disassembling the engine, clean the outside of the frame and engine thoroughly so to keep dirt and dust to out of the cylinder and crankcaseRemove all traces of gasket material from the mating surfaces of the cylinder head, cylinder and crankcaseClean all parts before inspectingBefore assembling, apply clean 2-stroke engine oil to all sliding surfacesUnder racing conditions, the piston and rings should be replaced after 30 hours of runningThe piston pin and small end connecting rod bearing should be replaced after 30 hours of runningOptional oversize piston and piston rings are availableRefer to Page 1-14
SPECI ICATIONSI
ITEM Cylinder head warpage Cylinder
STANDARD mm (in) 0.05 (0.002) 66.02-66.04 (2.5992-2.5998)
SERVICE LIMIT mm (in) 0.07 (0.003) 66.07 (2.601) 0.03 (0.001) 0.03 (0.001) 65.88 (2.594)