How much continuous cranking did you do with that starter? If it was a lot and that's still the 6v starter, you may have fried it. I'm still guessing that even after you get the starter motor figured out, there may still be something else. Did you ever get it to run after you rebuilt the carb? Was your fuel pump pumping strong or not? I'd say your first priority is to get the starter motor figured out and then you can cross that off the list. Also while you're ironing this problem out, I'd pull the plugs to reduce strain on the starter, and help save your battery.
