1981-1984 Official Honda ATC250R Shop Manual, Page 138Get this manual
r::iJ HONDA BRAKE MECHANISM (FRONT DISC BRAKE)
ATC 250R
CALIPER CYLINDER INSPECTION
Check the caliper cylinder for scoring, scratches or other damageMeasure the caliper cylinder I.DSERVICE LIMIT: 30.290 mm (1.1925 in)
CALIPER PISTON INSPECTION
Check the piston for scoring, scratches or other damageMeasure the caliper piston ODSERVICE LIMIT: 30.140 mm (1.1866 in)