Master cylinders can lock up. Mine was replaced under warranty.

 

Your in Illinois, Cold, I go for frozen water, Ice in the master cyl. Possibly use the wife's hair dryer and warm the master cyl, if you don't have a heated garage, also warm the calipers and see if that releases them. If you have a heated garage, roll her into that and see if it releases in a few hours. Then as others have said, change the fluid. Note I said warm the master cyl and calipers, don't over heat them and don't melt the rubber lines.
Just my thoughts.
Ride Safe, road hazards are everywhere!

 

Sounds like the MC is screwed up. Same thing happened to me. Had to replace the MC. Problem fixed.

 

I blead the brakes and all is working fine.. I ordered a rebulid kit also so keep your fingers crossed! Thats something I dont ever want to go threw again!

 

Did rebuilding the master cylinder resolve this issue? I am having the exact same issue on my 07 Ultra. I have rebuilt that mc and changed the brake lines. Everything looks fine, and the lever is returning completely. However, the mc slowly builds the pressure until the brakes lock up.

 

Change your fluid it may have moisture in it.I had a buddy that had his front calipers locked up on him at 70mph,dam near killed him.Problem .....moisture in his brake fluid,fluid got hot, fluid started boiling, calipers locked up.It's something that's often over-looked.

 

Thanks for the reply FastBagger. However, I've changed the brake fluid a couple of times, and no luck.

 

off chance, but did you use the same brand fluid and all that when you changed it? Possibly try a different fluid?

 

I used the fluid they gave me at the Harley shop. Probably dot 4, I can't remember. What I'm thinking is that for some reason the fluid is not being allowed back into the MC completely when the lever is released. That's why I thought rebuilding the MC cylinder might work. I've rebuilt the MC, and replaced the front brake lines (just to be sure they weren't collapsed internally), and it hasn't helped. Since it is gaining pressure on both calipers, I don't think the calipers are the problem. I really think it has to be the MC, unless I am missing something. I just didn't want to drop a bunch more money if someone else had already found a solution.
I've found this exact same question asked 4 or 5 times in different places on the internet, but no one has ever came back on the forum to actually say what fixed their problem!! If I get this solved, I will damn sure post the solution for the next guy.

 

The solution:

After changing the fluid multiple times and rebuilding the mc twice to no avail, I was about to buy a new mc. Then, I shined a bright light through it, and peered at the fluid return holes with a magnifying glass (my eyesight isn't the best) and I could see just the tiniest of occlusions in the perfect circle of light from one of the holes. I had previously tried to clean these by spraying brake cleaner through there and using a small wire, but it was obviously still slightly dirty. So, I soaked the entire mc in a jar of brake cleaner for 24 hours, then worked the wire around in the hole under the brake cleaner, then blew it out with compressed air. After all this, the hole is now perfectly round when shining light through it. I've had no more brake problems so far. Apparently, even the tiniest amount of restriction in those return passages can eventually lock up a brake.