Rear Brake - Resevoir empty after storage

[Anonymous]

First, my compliments to this forum. I lurked a bit when I got my GS a few years ago, but this is my first post.

1980 GS550E, 36K, all stock.

I just pulled the bike out of a 4 year outdoor storage. I know that's a mean thing to do, but it was unavoidable. I'm pretty sure this bike has seen more years of storage than use.

Anyway, the rear brake pedal was binding up. I lubed the pivot a bit getting it to move somewhat and found it wasn't generating any pressure. Then I found the resevoir was totally dry. I topped it off and it bubbled a bit. I loosened the bleeder screw to see if it was moving fluid, and it was. After all this I noticed the pedal movement had improved significantly, so now I'm thinking the binding was in the dry master cylinder, not the pivot.

I haven't had time to do a full bleed to see if magically comes back to life, but the binding scares me a little bit.

I'm sure I'll have to tear the whole thing apart, but does anyone have any ideas on how the system could drain like that? I didn't see any obvious signs of a leak.

Thanks. -J

[Anonymous]

OK, I know it didn't evaporate and must have leaked but has anyone seen this before?

Am I likely to have damaged the piston / bore by trying to work it free when it was dry? Are there o-rings in there?

Thanks

[argonsagas]

This can happen with any hydraulic system.

Since it went completely dry, you know for certain that there is a leak, but time has allowed everything to dry, so you are not likely to find the exact point now.

This is irrelevant, since the seals will have dried throughout and all must be replaced. The same applies to the flexible brake line.

Pull EVERYTHING apart, checking for damage as you go, and, if damage is not found, replace all seals and the brake line, refill, test, double-check and then ride.

While apart, you might consider a brake hone to give a clean and polished surface. Dry works, but I would use a light oil while doing it, and clean very carefully afterwards to get out every trace of oil and dirt .

[Anonymous]

Thanks argonsagas.

Am I likely to have damaged the piston / bore by trying to work it free when it was dry? Are there o-rings in there?

I was referring to the master cylinder here (I know the caliper piston sure wasn't moving!). Are these rebuildable? Clymer doesn't touch them other than an illustrated parts diagram.

What's the availability like on seals?

[argonsagas]

Better that I not try to answer all of this one. I have not taken one apart for a long time, and the last one was not a GS.

Generally, though, it is possible to have caused some damage by moving the parts when dry, but while damage would certainly occur to the seals, there is much less chance of damage to the walls of the cylinder, and serious damage to the cylinder (while possible) is even less likely.

A brake hone should take care of any minor scratches.

Remember to use a hone with fine grit, and use it WET. (oiled) Yes, this will reduce the friction, but it will do two positive things, 1-minimize material loss, 2-lessen the chances of error. Toss in frequent checks while working and those things add up to a superior job when completed.

[Anonymous]

A few years ago, I got my KZ 1300 out after sitting all winter, apprx 4 months. I found the same problem you have. The rear master & reservoir was completely dry. There was nothing on the floor nor on the bike that indicated a leak, but was completely dry. I filled the system, bled the air out, and to my disbelief the brakes worked perfect. No leaks, & after the following winter, may have not sat for hardly as long, still full of fluid. I never knew where the fluid went nor why, just know it didn't do it anymore. Same fluid still in it when I sold it a couple of years later