Is there a tutorial for rebuilding/replacing a rear master cylinder?

[Guest]

The other day, my rear brake abruptly went out. We're talking pedal to the metal dead in only a minute or two.

I got off the bike and couldn't find any leaking brake fluid, and the reservoir is still full. I bled the lines once I got home and replaced all of the brake fluid with no improvement.

I'm assuming that I'll need to replace, or at least rebuild the master cylinder... but I don't know how. Is there a step-by-step guide available? I have gathered from searching GSR that it's not a terribly complicated repair job, but I'm not sure how to proceed.

I've used the tutorials on Basscliff's site for all of my other projects and I'm pretty much indebted to them. Is there a step by step guide on rebuilding a MC? I'm also considering just buying a new MC, but I'm not sure how to install it and fill the brake lines. I haven't done any brake work yet beyond bleeding.

Thanks!
Kevin
Chicago, IL

[Kiwi Canuck]

Try this

http://members.dslextreme.com/users/storagecliff1/images/brake_caliper_overhaul.pdf

[eil]

A quick skim of BassCliff's site doesn't reveal a tutorial for a master cylinder rebuild, although my tired eyes might be missing it. (The one mentioned by Kiwi Canuck appears to be for calipers.)

Anyway, the master cylinder is pretty simple. I would just remove yours from the bike, take it apart, and see if you can find anything obviously wrong. There are two seals inside, one or both may have gone bad. Do try to keep the order of the part straight, because they must go back inside the cylinder in the right order. The only time you need to replace the master cylinder itself is if the bore inside is scratched.

If you need new MC parts, go to the OEM vendor parts diagram and look for an item called "piston and cup set". This will have everything you need to rebuild the MC.

As long as you have everything disconnected, I would also open up the rear caliper and inspect/clean it as well.

And finally, if you don't have stainless steel lines, now would be a great time to add them.

When you re-connect the brake line, always use brand-new crush washers.