My disc brakes won't disengage PLEASE HELP

Recently bought a XJ550 Seca 1982, and now have a front brake issue. The front brake will not disengage from the rotor. I have two calipers with the same issue so I don't think they both are be sticking,

What I have done
1. removed piston and cleaned all parts
2. bleed brakes multiple times no air in system
3. Brake lever is new so i don't think that is sticking.

Please HELP, not sure where to go from here?

 

Welcome to the site! Sounds like the caliper piston may be sticking. When the caliper piston is rusted or has a lot of debris,it often limits retraction. The piston needs to be smooth,with no surface imperfections whatsoever. If the brake activates but doesn't retract,it will cause the brake to drag. Also,make sure that the screw that contacts the master cylinder plunger is adjusted properly. If this doesn't help,I am confident that another member (with more wisdom than myself) can point you in the right direction. Best of luck to you!

 

Great thanks for the welcome and reply, I popped out the piston and cleaned it and cleaned around the square seal, seemed ok, I will investigate on the screw to the master cylinder.

 

In the bottom of your master cylinder there are 2 holes. The larger it draws from the smaller is the return. If the return is plugged it wont let the pressure off the calipers.

 

Thanks, any tricks for cleaning?

 

Very small wire or guitar string.

 

I use a single bristle from my parts-cleaning brush clamped in a hemostat. Wire or guitar string can scratch the bore of the hole.

 

Probably a blocked return hole.....BUT.....make sure your brake pads are wearing evenly. I had a BMW GS lock the front calipers because the pads were worn tapered and skewed the caliper pistons in the bores so they would not return. A new set of pads fixed it.

 

Great thanks for the responses, fingers crossed.

 

See,I told you these guys are good!

 

Ok, So I think I cleaned it pretty good, actually see brake fluid come up the small hole when I squeeze the brake lever, but still have the problem, piston will not fully release. Any other suggestions PLEASE!!

 

I think you have floating callipers on that bike, make sure they can move freely on the retaining bolts.

 

The 550 caliper floats on what is called a "sliding pin." It is not uncommon for this to become a "beat it with a big hammer" pin, which will cause the brake to hang up.

You'll need to remove the caliper, and disassemble it from its holding block. Clean and lightly lube the sliding pin and shim plates, and be sure the pin boots are in good shape. Even though the Yamaha 550 fiche doesn't even LIST the pin boots, our man chacal carries them.

You may need to replace the sliding pin if yours is corroded or rusted beyond ever being smooth again.

Both my 550 Secas had/soon developed the problem when I first got them; and in both cases it was the holding block corroded in place on the sliding pin causing it.

If you need a diagram or pic, just holler.

 

Sweet thanks all, took it for a test ride last night, and seems okay.

 

Another happy customer.... Go now, ride in peace

Rob

 

Chuck the pins in a drill. Spin the pins and polish with sand paper. Quik and easy.