My tractor will not turn over. I removed the starter and tested it using the same battery that's on the tractor, and it spins fine. I put it back on, it will only click. I bypassed the switch, still only clicks. I took the starter to an Amish guy who works on them and he said he sees no problems with it. The tractor has always turned over extremely slow. It's a 54 To30 6v positive ground. The motor seems to be free. I also tried turning it over with the plugs all out, and the starter still only clicks. Any advise?