I have an all terrain 70 that would not work intermittently. I disassembled the motor and discovered that the brushes wer hung in the brush housing. The housing is clean and the brushes are in great shape. It appeared that the geometry of the brush spring is just right to make it hang at that prticular position. I freed the spring and could not recreate the problem. Reassembled with new gaskets and seals and all is good.