Bfh?

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Sounds like you have crap in your system somewhere not allowing the fluid to move back into the master cylinder.

Did you get the pistons back into the same cylinder they came out of?

I would open the bleeder on the caliper and put a clear hose on it with one end in a bottle and fill the master cylinder and then press it a few times to see what comes out of the bleeder.

 

Don't know what "bfh" means.

Yeah I thought maybe there was something in the lines still but when everything was disassembled I cleaned it pretty thoroughly. Flushed with alcohol and dried with compressed air. I have a single piston front brake, so it has to be in the same place it was removed from.

 

I had the same problem. I took the piston out of the caliper and took some emery cloth and lightly sanded the cup the piston rests in. worked great! there was a small ridge worn into the cup that was binding the piston. it was so small that you couldnt see it but just a little sanding smoothed it out.

 

Have you tried to open the bleeder when the brakes are locked up? If fluid squirts out and brakes free up it is in the master cylinder. If it does not it is in the caliper. With what you said I would look in the master cylinder. There is a small return orifice in the reservoir.That could be stopped up. This is not the larger feed hole but a small return hole. When you are bleeding the brakes pump the handle and crack open the banjo fitting first. Air gets trapped in this fitting and makes bleeding harder.

 

I haven't tried the test with the bleeder yet. It was too late when I posted this before to do anything. I will give it a try the next day I have available to work on the bike.

I have also not tried any sanding but it sounds like could fix the issue, assuming something is not perfectly smooth anymore. I'll give that a try and post the results back here. Unfortunately it will not be until Thursday at the soonest that I have time to check into this stuff.

 

Got to work on the bike again today and I did the test with cracking the bleeder. It seemed to just slowly dribble out, not squirting, so it doesn't seem to be under pressure. There is also a small squirt from the relief port when I press the brake handle. My suspicion is in the caliper now, though I don't know what it is.

I hit the piston and piston bore with some 1500, then 2000, then 2500 grit sand papers and put it all back together with no real difference in performance. I managed to push the bike out of the parking space here at my apartment and ride around the parking lot and it stayed bound up tight. Not really sure where to go from here except for maybe some more aggressive sanding on the piston. This is very frustrating. I want to ride my bike again!

 

A final update: after taking apart the caliper again I could see visible signs of damage on both the piston and the caliper where the metal was too tight and had begun to burnish. I cleaned it up more aggressively and put it back together, only to now have the piston totally seized up. Neither compressed air nor small pry bar could make it budge. Caliper shopping begins...