1985-1986 Honda ATC250R Shop Manual, Page 207Get this manual
HYDRAULIC DISC BRAKES
Push the dust and piston seals in and lift them outClean the seal grooves with clean brake fluidCAUTION
Be careful not to damage th_e_ Pis_t_o_n_ sliding surfaces
INSPECTION
Check the caliper cylinders and pistons for scrat ches, scoring or other damageMeasure the cylinder inside diameter and piston outside diameterSERVICE LIMITS: CYLINDER 1.0 PISTON 0.0