I received a 601 basket case in a box. I have it mostly back together and running but there is a problem. The ball bearing is in place, the thrust washer is there, and the brush cap is the correct one. It will go around the track by itself with no load, but sometimes starts with difficulty. When you add cars it won't go and the motor loads down. I see the armature is rizing up against the brush cap when this happens. There is 1/8 th inch gap between the armature and the brush plate. What is wrong here? I am sure I have all the right parts in place.
Rob