Brake handle plunger is in all the way... need some help

[Nick]

I got my parts today from a fellow member and I'm trying to get the front brake handle / master cylinder on tonight and the carbs tomorrow. I got it all hooked up and filled with fluid. I'm trying to bleed the brakes but the plunger thing is in all the way and wont come out! How can I solve this problem?

ps. I searched for like 5ish min to find a solution.

[80GS750]

well....

pry the pistons apart and force the fuid back into the reservoir.....

otherwise if that doesnt work you may have to take it all apart and rebuild it...

if the spring wont push it back the rubber inside is bad and its toast

[Nick]

So i should take that rubber thing around the piston off then? I'm thinking thats what you mean but i want to make sure first

[Zook]

Your master cylinder may need cleaning/rebuilding. Did you disassemble and clean it?
I'm in the process of doing this on my recently purchased 80 GS1000G.
The brake fluid was like molasses and the caliper pistons were stuck by the gooey brake fluid. I almost didn't get one caliper piston out. Took lots of soaking in brake fluid and applications of compressed air and a c-clamp pusing the piston back in.
The master cylinder piston would not return (what you are describing).
Upon disassembly it was no wonder it wouldn't retract, it was full of muck.

This on a bike that was licensed two years ago...the PO is a retired airline pilot and owns/maintains his private helicopter...remind me not to ride with him.

[Nick]

so there's a way to take it completely apart? I'll most likely need a little bit of guidance to do so. Taking apart would be like... removing the handle, removing the little boot thing, taping the piston out, and what else?

[SqDancerLynn1]

Their is a clip too that needs to be removed before the piston will come out

[Nick]

where's the clip?

[J_C]

Once you get the handle off and the dust cover out you will see it. It's at the end of the piston. Its easy if you have circlip pliars, though very small long needle nose MIGHT work, not sure.

[Matchless]

When you have it apart, clean it well and make sure the small hole into the reservoir is clean. Without the rubbers on the piston the metal piston should easily slide into the bore of the M/C. The bore should also be perfectly smooth.
Download the service manual or put this attachment on your PC and enlarge.

[Nick]

my M/C looks different than that one but i'm sure the internals are all the same. The only difference is the cup is like an actual cup instead of a rectangle and the bolt for the brake line to the caliper is on the end by the tach.

[Matchless]

my M/C looks different than that one but i'm sure the internals are all the same. The only difference is the cup is like an actual cup instead of a rectangle and the bolt for the brake line to the caliper is on the end by the tach.

The "cup" is actually the reservoir, and you have the round one. There are similar diagrams for those if you download the manual. Have a look at BassCliffs website.
Yours may have some corrosion inside if it was not used for a long time and you need to rather clean it out properly before using.