front caliper

I'm still looking for the split caliper to take a pix.
The crud is corroded aluminum.
You can lightly hone the caliper bore mainly for crud cleaning. The piston DOES NOT normally touch the bore. In use it completely floats on the square ring. The ring is ever so slightly smaller than the groove. with brakes on it squirms outward then on release it unsquirms to relax and remove the push on the pad. this prevents drag of the pads. when the piston drags on the bore it will not function well.