Rear Brakes Locking up on 98 ABS

Gentlemen / Ladies. I have had my 98 ABS since new and have religiously bled the brakes every fall before putting the bike to bed for the winter. No problems so far. Last fall I missed a lot of things, including putting my bike to bed properly with a bleed and oil change. Recently i started riding again but I had some sticking issues with the rear brakes and figured on doing not just a bleed but a rebuild as I had read that my problem was likely a sticky piston. No problem, got a kit, replaced the seals etc, however, now the rear brakes completely lock up. Fronts are fine. Obviously, the problem is not in the caliper, but somewhere else.

Ideas?

Not sure, so will throw some ideas your way... I think the ABS models have linked brakes with a modulator valve and such. When you say that you bleed the brakes every year before putting it up for the winter, are you just bleeding or are you flushing out the system? Could be some gunk stuck somewhere in the system and causing a back up of pressure. Try a vacuum pump and assist it with rear brake pedal pressure when flushing it. Make sure the pads are seated in the caliper properly. Might be a "control" issue with the ABS system itself... I am not familiar with the ABS models. Wish I could help more.

Vinny; Yes, I bleed until I get clear, clean fluid with no bubbles out of the nipple. I follow the prescribed sequence as well. And when I changed out the seals and springs etc on the rebuild, I flushed out the system again. I suspect that it is a control issue with the ABS, but I do not understand that part of the system. Hence my question.

jfheath; I suspect your comment on the front is right. After finding the rear locking up, I tried to bleed the system as per the manual, front left, front right, rear front, rear back. Well, neither front will bleed. So I am thinking master cylinders. Also, the linked braking is not working, (when I apply either the front brake or the rear brake, the opposite (the outside pistons) do not engage). So, I am now thinking that this all has to do with either the delay valves or the master cylinders. I suppose that I will need to take them apart. I am starting to think that I need to trailer this to the shop and have the professional spend some time on it. Thanks for the suggestions.

A couple of months back after replacing brake pads and partial bleeding on my 2010 ST1300, my rear locked up on me. The only way to release the pads was to crack the bleeder valve. Byron and I rebuilt the SMC, Rear Brake Caliper and the Foot pedal MC. We then did a complete flush and that cleared up the issue.

We weren't 100% sure, but I really do think my problem was the Foot pedal MC.