550 rear brake problem

[Dking686]

So I've never owned a bike before, and have been graced to get a hold of a '80 550E. I'm learning as I go, and loving every second of it, but right now I'm stuck. The rear brake on her is unresponsive, I press down on the pedal and can see the wire coming in and out of the master cylinder, but nothing happens at the actual drum on the rear tire... Any ideas of what it could be? I can post a few pictures of the brake assembly if that would be helpful, I just don't know what to do

[hampshirehog]

Hi. You don't have a drum brake - you have a disc brake and that works quite differently. When you say nothing happens do you mean you can't see anything or does the brake not work at all?

[Gonzo]

Master seized up sounds like. If the brake systems aren't properly flushed and maintained they will corrode and seize up over time. Sounds like it's time to take the system apart and rebuild it. It's fairly cheap, it's easy enough given you have the proper tools, and it's probably one of the most important things you can do to keep you and your bike safe.

I'd plan on rebuilding everything if I were you, front and rear. Master cylinders, calipers, and I'd get some new brake lines too.

All this of course is just speculating given the lack of info here, but there really isn't too much that can cause that kind of problem really. And given that the bike is nearly 30 years old, I'm willing to bet that's it.

[Dking686]

Gonzo and hhog- Thanks a bunch, could you put me in the direction of a good site to order everything from? I need all the help i can get...

[hampshirehog]

Does the brake work at all? You might end up buying bits you don't need if it does.

[Gonzo]

First thing is first. Trouble shoot.

Fluid is topped off? No lines are leaking? Lines are connected at all? All that obvious stuff needs to be checked before diving in and ripping things up. If the basics are in order then it warrants a tear down and inspect. You can't really go ordering parts if you don't know what you need. You might only need seals and boots, or you might have really bad scoring and pitting on the pistons and bores and need new metal parts too.

Do you have a Clymer's for the bike?

[Dking686]

[QUOTE=Gonzo;1639661]First thing is first. Trouble shoot.

You couldn't be more right... Rear brake has no fluid whatsoever, time to get a bleeder kit and some fluid- the manual says DOT 3 or DOT 4, is one better than the other?

[cowboyup3371]

Tear the brake caliper apart first and rebuild it. New seals are necessary and you don't want to just leave old gunk in the caliper. This way you'll also know if the piston is badly pitted which will cause you even more problems. You can and should get the rebuild kit for the caliper as well as the rear master cylinder.

Make sure the return port in the master cylinder is cleaned out and open (so small it's hard to see but vital to do) or you'll end up in the ditch when your rear wheel locks up on you.