I have a Harley Ultra Classic w/ Mystery Design trike kit. Having rear break problem. Sometimes I have good firm brake and other time the peddle goes to the floor. There are no leaks. Have installed two new master cylinders, took the caliper apart and cleaned it. It has a steel braided brake line. Have bled brake several times. Nothing works. Mystery Designs says call caliper company which is Wilwood. They said "Very interesting". Would like some real advise.