I got a single sided 6 piston on my 13" rotor and the other day I felt the bike slow down really fast. I grabbed a fist full of front brake and let it go really fast and it seemed like it went away. I got 700 miles to do over the course of the weekend so I decided just to check it. The rotor has small grooves from the caliper dragging. I got a 13 ultra and I'm unsure what to try first. I bled the brakes once and next up is shims but I'm unsure if the caliper is actually returning to its original state after I grab the front brake.

 

From your description, it sounds like the brake pad is cocking, creating the drag. Your brake application re-squares the pad, fully releasing it. Until it next drags or wiggles itself into a cocked position.

I know of various 6-piston calipers, but not one that has 6 on one side only. That would be a very long caliper. Are you sure you're describing this correctly?

 

You said theres grooves on the rotor from the caliper dragging. The caliper should never touch the rotor, sounds like it is not shimmed and the rotor is not centered between the pads allowing equal movement. Hows your wheel bearings?

 

I have one Rotor and Piston on the left side. (Single Sided) Sorry. Pad may very well be cocked because I had no problems dragging until recently. Ill remove the pads and clean all surfaces, reseat the pads and hope for the best. I can see the rear of the pad sticking out and not contracting after the lever is released. Wheel bearings are good.