If servicing or repairing your wheel cylinder, start by washing the cylinder and
Pistons with only clean brake fluid or brake cleaner, not anything else. Dry the insides of the cylinder and the pistons using compressed air after cleaning, because towels or rags can leave lint that sticks to the parts of the engine. There should be light and dark stains in the bore, but if you see any scratches, pits or corrosion, the cylinder bore needs to be changed. It is fine to polish the bore without a crocus cloth, but don't try to hone it. Make sure the pistons are not scratched, have no scoring and are free of corrosion; replace them if you find any damage. Trash the old piston cups, springs and expander, but keep the original dust boots if they are still in good condition.