Brake issues, no pressure and little piston movement?

[Stabler]

I've searched this site and I've went through the manuals, without any luck. Maybe one of you more experienced guys can help me out?

My problem:
My master cylinder was hanging upside down for a couple of weeks while awaiting new handlebars (stupid I know). Before that I had the front brake locked up, but freed it by forcing the piston back in in the caliper then press it out with the brake lever. Worked fine after that for several miles.

Now for some reason (after sitting for a month or so) I can't get it to brake the front wheel. I have almost no pressure when I press in the lever. I tried to bleed it, but after pumping like 40 times then releasing the bleeding nipple I only got like 1 cl of brake fluid comming out. I repeated this 6 times - no difference.

I noticed (when having the bleeding nipple tightened) that my brake piston moves like 1-1,5 millimeters when I press the brake lever, but when I let go the piston return to its starting point.

Does anyone recognize this behaviour of the caliper? Is there a "quick fix" or do I just have to tear the caliper and M/C apart and clean 'em out? (I really don't wanna do that, but if that's the last way out - I'll have to do it).

Any help or pointers here would be widely appreciated.

(Please excuse the poor writing in english - I'm swedish).

Thanks, Stabler.

 

[63-Coupe]

The fact that you had to force the caliper back in is a clue that it may be rusty, siezed, or partially siezed. You might have got it working by forcing it then even with that short time sitting it siezed up again. Until you determine that situation how far the piston moves is irrelavent.

The other thing is, you don't say exactly what procedure you are using to bleed the brake system. Are you closing the bleed screw before releasing the brake lever? Don't take this the wrong way but you would not be the first person I have seen release the brake before closing the bleed screw.

 

[DanMach]

If it were me, I'd just get a new caliper.

 

[jmd_forest]

After 30 years it makes reasonable sense to rebuild the caliper, master cylinder and replace the brake lines. I am the cheapest person I know and am renowned by my friends and family for my cheapness but on a bike the brakes are about the only safety system you have. I suspect it may be time for a rebuild.

 

[Stabler]

Yeah - I kept pressure 'til I closed the bleed screw before releasing the lever. (I've bled a ton of car brakes).

So - I best get me some new parts and start rebuilding shit then.. Damn..

Thanks guys, really appreciate it.

 

[jayel]

the fluid return hole in the master cylinder may be plugged if it's not pumping correctly, what year bike?

 

[Stabler]

It's an '82.

 

[jayel]

OK there should be two holes in the bottom of the reservoir cup, a larger hole 1/8th" then a small hole (fluid return) that get plugged very easily, poke thru it with a wire strand from copper wire or a bristle from a wire brush, once you get it pumping ran about a half a can of brake fluid thru the system (until the fluid come out clean) won't be as clean as pulling it down and cleaning but a heck of a lot easier the caliper is easy enough to take apart and clean so no reason not to

 

[Stabler]

Allright! Thanks man! I'll try this first.