1985-1986 Honda ATC250R Shop Manual, Page 210Get this manual
HYDRAULIC DISC BRAKES
INSPECTION
Check the caliper cylinders and pistons for scratches, scoring or other damageMeasure the cylinder inside diameter and piston outside diameter
SERVICE LIMITS: CYLINDER 1.0 PISTON 0.0
25.46 mm (1.002 in) 25.30 mm (0.996 in)
ASSEMBLY