1981-1984 Official Honda ATC250R Shop Manual, Page 53Get this manual
r:::iJ HONDA ATC 250R
CYLINDER HEADCYLINDERPISTON Inspect the cylinder bore for wear at three levels in and directionsTake the minimum figure measured to determine the cylinder wearAvoid the port areaSERVICE LIMIT: 70.050 mm (2.758 in)
Measure the piston 0.0at point 10 mm (38 in) from the bottom of the skirt and 90 degrees to the piston pin holeSERVICE LIMIT: 69.870 mm (2.751 in) Calculate the piston-to-cylinder clearance SERVICE LIMIT: 0.150 mm (0.006 in)