Sticking front brake, help?

Hey all, been a while! But I'm back lol! With questions!

So I was getting my 1980 XJ650 ready for spring riding, and I noticed that my front brake is stuck, the front wheel wouldn't roll at all. It did this same thing last fall, too.

The brake caliper has been rebuilt, and my lines are braided stainless. I got all the parts from Len, a few years ago. I rebuilt the master cylinder last fall when the front brake stuck like this the first time, figuring that was the problem. Then we bled the brake lines again, made sure the brakes were working properly, and it's just been sitting over the winter since. Now it's stuck again.

When I opened the master cylinder yesterday, I can tell there isn't any dirt or anything blocking the return, the brake fluid looks perfectly clear, with nothing floating in it. Any ideas how this happened, or what I should do? I did already take the caliper off so the bike will roll until I get this fixed, but that's it so far besides checking the inside of the master cylinder.

Thanks ahead of time for any help!

 

The caliper has trash keeping it stuck. Take it apart and clean it real good. Its common for brake fluid to harden up around the seals and make the piston stick. I have to clean mine every 2 or 3 years because of the same problem.

 

before you get real involved, maybe it's just stuck from setting all winter. since the caliper is off, just pump the lever a few times and then push the pad back, remount the caliper and see how it works. there's nothing to push the pad back but the flex of the seal, once it's worked loose it might be fine