Brake Caliper Stuck Shut

Hi,
I am in the process of changing my left fork seal due to it leaking on my 1982 XJ750. My problem is when I took off the front tire I noticed that the right brake caliper was stuck shut and I was unable to put the tire back on without taking off the caliper. The pads are stuck together and I can't get them to come apart at all. The piston is completely stuck. I already tried shooting some compressed air in there and also tried pumping it with the brake line hooked up. I am stumped and would like to get this fixed so I can get out and ride. Does anyone have any suggestions? Should I take it apart. If so, how do I take it apart?

Thanks

 

You must have grabbed the brakes a couple times in order for the pads to be fully extended...

If you fully extend the piston of a brake caliper it will get lodged in the bore and you might as well take it apart and reassemble it. The bores in the caliper aren't cylindrical and actually are more hour-glass shaped to allow the piston to move some so it can remain in contact with the pad. When you fully extend the piston, it will oftentimes get lodged on that high spot and is a lot easier to reinstall off of the bike without the backpressure from the brake fluid. Unfortunately, bleeding the brakes on these early '80s bikes is a huge PITA so you'll have to put yourself through that one.

 

I doubt it is stuck, they are just hard to press back. By blowing compressed air in it, and pressing the brake lever, you are just making it worse. You are re-creating the pressure that is forcing the brake pads together. Just take a C-Clamp and press both brake pads towards the piston side. Then you can slide the non-piston side pad back open so you can slip the rotor back in there.