GS850G Rear Master Brake Cylinder

[slither]

'79 GS850G, been siting a few years, not sure when the rear brake actually worked.

Is there any trick to getting the piston/cup/spring set out of the rear master? When I pull the circlip and the pushrod, the inner bits don't want to come out. I can feel the spring and cup through the banjo bolt hole, so it's the bottom component that's frozen. I have it soaking in brake fluid hoping to free it up better than hitting it with brake fluid. Would it be helpful to remount it, and try using the brake pedal to break it free?

Even if I get the piston/cup/spring out, I'm afraid the bore will be pretty boogered up. The only good news is that it looks like I can still get a NOS master.

 

[2BRacing]

Wrap the master cylinder in a rag and apply compressed air to the banjo bolt hole side.

This should expel the piston - but beware - it can come flying out, so wrapping a rag around it is a safety measure!

 

[fastbysuzuki]

The chances are there is a burr around the circlip groove stopping the inner's to come out, if you have a curved scraper or the like run it around the edges of the groove to remove the burr and it will likely come out.
And use 2B's idea if it's still a bit stuck.

 

[slither]

Air gun sounds like a good idea, and now that the obvious is mentioned, I can try the grease gun trick as well. Will need to block off the inlet from the reservoir as well, I assume.

I'm *usually* good about keeping dangerous stuff pointed away from myself. Occasionally have to watch my husky, he's so used to shenanigans he doesn't usually move unless something touches him. As in I was wheeling the bike around within inches of his nose a couple days ago, and he just kept laying there trusting me not to hit him. He gets up to leave if I use the grinder too long though.

 

[salty_monk]

I fitted a master of an EX300... the innards of the old one were not pretty. I'd expect yours to be in similar condition. I didn't investigate this option but a V-strom MC also looks like it could be made to fit.

 

[slither]

I fitted a master of an EX300... the innards of the old one were not pretty. I'd expect yours to be in similar condition. I didn't investigate this option but a V-strom MC also looks like it could be made to fit.

Huh, I've been trying to avoid too much interchanging, but I'm sure it'll come!

Got the old one apart using a grease gun, so now I have a box of bits ordered to finish putting the carbs together, rebuild the petcock, fuel gauge sender, etc. Will need to clean up my spare tank, I'm going to try my hand at spray painting it, and worst comes to worse, there's always bedliner.

Playing with spray paint and acids will have to wait a bit though, just did eye surgery, and according to some, chemicals/dust in healing eyeballs isn't... great.