I have a 1974 Norton 850. The master cylinder is in dire need of repair. The piton measures .620 inch so i Believe this is the standard 5/8" piston. I have read about replacing this with a 13 mm kit. Can someone recommend a place in the states that can rebuild this for me? is this something normal people can do in their shop or does it take a machine shop? I plan to bead blast all the corrosion and paint off the outside of the cylinder and repaint it. Any recommendations on the paint?