I was riding my 71 Cl today and I was going about 40mph and hit the back brake(but just moderate pressure) and the thing locked up and stayed locked until I came to a stop. I was sideways a couple of times and I'd like to fix this problem so I don't have to wear diapers every time I ride it. What happens is I give the back brake(drum)moderate pressure and the pedal feels like it pumps up and the brake locks, until I stop moving, when it frees up again. The linkage isn't binding, and I'm going to go ahead and take the wheel off, but I was just wondering if anyone knew what the problem could be. Thanks, Jimmy.