I just received my clutch and brake master cylinder kits from Bevel Heaven. They are identical to the parts in my reservoirs, but I've run into a problem.
I disassembled the reservoirs 2 months ago for powder coating; assembly is pretty straight forward, but something is wrong! The pistons slide right through the opening in the bore and through the and cap/retainer! In other words, most pistons are retained in the bore by a C-clip and a washer, but that doesn't work with mine. The pistons just jump out!
I know I'm not missing anything, in fact the kits brought an extra brass washer that my reservoirs didn't have. So what the heck holds these pistons in?!?!

Rick

Hi Rick,

The circlip sits in a groove in the casting of the of the master cylinder and this holds the piston in. Could this groove have been filled in the powder coating process?

I have to admit that I actually ended up going with a 916 master with a remote reservoir in the end. Even with the overhaul kit I never got my original master cylinder to build up enough pressure, or it started leaking .

Cheers,

Mike

No, no powder anywhere near the bore. Maybe the clip is not in the correct groove...I'll try again.
Thanks

Definitely call Steve at Bevel Heaven and see what he says.

I have no experience with the stock parts on the Paso master cylinder, but I have had this exact issue with several other models of Duc's.

The little white retainer in this photo is what prevents the piston from popping thru. The ID of the white retainer is large enough to let the MC piston thru, but not large enough to allow the O ring seal thru. If your O-ring is badly worn, the piston will pop thru, and likely tear the rubber boot in the process.

The extra brass washer you speak of is for models that don't use the circlip, instead that washer is carefully tapped into place, and serves the same purpose as the circlip, but in a much more fragile way...

Two notes. In the photo below, the white retainer is on the piston upside down. Narrow end should point down into the cylinder bore. (this is a 1998 Duc 748, virtually identical to most MC's from '94 thru 02 or so)

Also, if you've got a Ducati with a more modern MC, you can't buy these rebuild kits, thanks to lawsuits. If you're going thru the MC without a rebuild kit, note that Viton o rings REALLy don't like brake fluid, neither do Buna-N. HNBR is better, but not great, the best is EPDM.

Ok, that makes more sense. I wasn't putting the o-ring inside the bore, just outside of it Lets see what happens today...
Thanks