Some of his motors are a little strange on some power supplies. Sounds like you might have a 6volt motor. Try replacing it with a 12volt motor. I have one of his machines and every now and then it stops, but if I hit the peddle again it comes right back on. When it makes me crazy enough I will just grab a 12v motor. They aren't expensive and it would most likely be cheaper than sending it back to him. Regardless he will sort it out I am sure.