Hit rock and broke rim now rear brakes are dragging!? Need some help on this one.

Last fall I hit a rock and it dented and broke my front rim. The wheel rotated many times and hit the left caliper eventually stopping and then was unable to drive the bike onto the trailer because the rim bound on the caliper. No aparent damage after close inspection of caliper.

1. I have replaced crush washers on the brake left front caliper, the highest brake line. This was due to a leak on the fitting. Bled brakes according to bleed procedure. No leak now. Brakes still dragging.
2 Drove the bike uptown to wash it off. Brakes were locking up or dragging hard.
3 Bled the system 3 times. Brakes still dragging/locking.
4 Cleaned the rear pistons. Brakes still dragging/locking.

This has all been done and tested on the center stand. The rim needs quite a bit of pressure to turn.

I have not taken the bike around the block to see if they quit dragging. Not sure if this matters.

Do i need to put a new secondary master cylinder in? What do you guys think? Thanks guys!!!

Did the impact throw the wheel out of round and warp the rotor? You don't say that you tested the rotor after you replaced the broken rim. I would push the pads away from the rotor (as if you were changing them) to free up the wheel and rig up a dial indicator on a stand to check the runout of the new rim and the rotor. Obviously the rotor is more important than the rim, but there are probably specs in the manual for max runout of both.

Another possibility is there is some hidden damage to the caliper. There are square section rubber '0' rings inside the caliper that seal against the piston. Apply the brakes and the ring distorts slightly as the piston is pushed out against the pad. When you let up on the brake lever, the slightly twisted rubber ring pulls the piston back into the caliper and therefore the brake pad away from the rotor. We are only talking a few thousandths here - it doesn't take much to knock the caliper out of alignment so that it binds on the rotor. If the rotor is not warped from the impact, then the mounting or the caliper is suspect.

Just to be clear, you have a ST1300 and not an 1100, correct? Can you be more specific as to which brake caliper is dragging since you talk about both the left and rear calipers...

It sounds like it's just the rear brake that's dragging. Have you tried actuating the SMC manually to see if it pivots freely? Did you tilt the SMC while bleeding the brakes? Do you use a vacuum device to bleed them or a Motion Pro?

Check to see if the fluid is returning to the master cylinder when the brake lever is released. If the tiny orifice is obstructed with debris (which could have happened when the front end took that hard of a hit), the pressure would not back off much. An easy way to check this would be to try spreading the pads apart. It should only take moderate pressure with a tool you can get between them. If it takes a lot of force, then your return circuit needs cleaning. To clean or dislodge debris from the return orifice, remove the deflector spoon at the bottom of the master cylinder, insert a small wire in the orifice (Make sure you are wearing safety glasses because the pressure relief may squirt brake fluid across the room).

The bike is a st1300. I think the front left disc is 100% straight. I replaced both rims. The front rim wasn't damaged enough to throw the disc out of true. I can only pivot the smc maybe a 1/8 or less. How far should it pivot? On my phone now at work can take pics and go into more detail tonight. I'm leaning towards a new caliper sub assembly or rebuild.

Update!

Installed new smc piston and all is well. Time to go for a rip.