R100RS rear master cylinder

[Jean]

There is NO circlip.
The largest steel rod that will fit thru the nipple hole is what to use to push (knock) the cylinder free.
My replacement parts were no different from the original. Got them from Touring-Sport BMW shop. They usually have what I need, for a competitive price (don't have to pay shipping and can examine parts on the counter).
They say: "we've been keeping these (whatever parts) for when you would call."