Rebuild kit for rear master on 1978 Kz650sr

Does anyone have any idea where I can get a rebuild kit for the rear master cylinder on my 1978 Kz650sr? I can't seem to find one anywhere, there are not even any cheesey chinese kits on flea-bay. Or do I have to buy another used master cylinder?

The piston may be difficult to find. The primary cup is available at a couple places. Do you know which parts need to be replaced? Ed

www.dealercostparts.com/pages/oemparts#/...0-D1-1978/070053D-11

I went through the same thing a couple of years ago. I don't think anybody makes a kit for that mc. I ended up buying an NOS piston plus the other parts separately. Sure wasn't cheap though.

Try Z-Power. They should have something for you.

This part is unobtainable for the early 550's too. Unless a NOS part turns up then replacing the master cylinder for something newer with the same bore size and similar bolt spacing is the work around.

While it's always best to replace old rubber bits, often times you can get away with reusing parts like the piston cup. Before attempting to rebuild an old master you need to inspect the bore carefully for pits in the aluminum. Clean out all the crud then use a flashlight and magnifying glass and look down inside. Sadly, water in the brake fluid often eats up the piston bore rendering it scrap metal. Finding a clean master can be a big hassle. There are companies that will press a steel liner inside so that can be a fall back plan (but not a cheap one).

No eBay APP ID and/or Cert ID defined in Kunena configurationNot sure if you need this or even if it's the right part, but here is an NOS primary cup on eBay: