How do back brakes work? I was at the track and all of a sudden they went weak. Well I thought it was the master cyclinder so I ordered one. I put a brand new one on and it did not work. The brakes would bleed out the way they should but it would not move the piston out of the caliper. There was no leakage any where around the piston either. I will tell you I have a caliper coming by the end of the week. What else could it be? Please help. My wife is going out of town next weekend and I want to ride all weekend.