For 6 weeks I've struggled trying to get my tractor running smooth again. I've put in 2 sets of points and condensors. New plugs. New coil. New battery. Each time, it runs good for about a minute and a half. Have to polish the points after the minute and to get it to run. Thought the new battery fixed it, but it still runs rough. Could I have a bad alternator? It's a GM internally regulated unit.