Hello. I am in the process of resurecting a 1981 Pantah 500 in my shed and am having problems freeing seized master brake cylinders (both of them). Any suggestions? I was then going to use them to free the seized calliper pistons (all 3). If you have any other suggestions regarding the Pistons I'd be grateful. Thanks. Tim
Airline gun up against the brake fluid inlet hole on caliper. And a piece of word to stop the piston flying across the room.
If the Master cylinders are corroded that badly then sadly replacement would be my answer because even if successful in freeing, the bores will nearly always need sleeving anyway. Unless you’re a sticker for originality you might find some later equivalent models that will fit the bill if the original items prove hard or expensive to replace. If the slave cylinders aren’t too badly corroded then you could use compressed air (as said already) to free them off. I appreciate you may not have access to this but it certainly works in most cases.
Immersing them in diesel for a few days might help loosen them off. You can get spares for a rebuild and complete master cylinders and calipers from Ducati Paddy, who I highly recommend. You can also get them from Gutsibits
Depends what you mean by seized. * Is the piston stuck so that it won't move to and fro in the bore at all, even when whacked? If so you will probably need a replacement master cylinder. * Is the piston able to move to and fro but the fixing ring rusted in place, stopping the piston from coming out? In that case it might be repairable so worth persevering.
There is a ring of spring steel which snaps into a groove in the bore, quite near the outside, and keeps the piston from coming out. It is not actually a circlip, although it has a similar effect. In good condition, the ring pops out fairly easily - if corroded in place, it can be a struggle. If you buy an overhaul kit it includes the piston with pressure seals, the spring, the outer seal, and the fixing ring.
