Farmall A will not start when warm

I thought it was vapor lock but I checked for spark out of the magneto and I can not see a spark when I try a warm restart. I can see a spark when I try to start it cold. It has the original magneto. I recharge the battery with an alternator.

Tractors history

I have a Farmall A that my dad got in 1978 when I was 15. He traded his boat with a stuck motor. I was really the only person who used the tractor over the years. I converted to an alternator when I was 17 because I didn't have a 12 volt battery charger and my dad would not let me get one. Someone gave my an alternator and somehow I got it to work. There was no Internet back then and I just worked it out by trial and error. Mostly error. It has a woods L59 belly mower I put on when around 1988.

I was not using it recently because the seat had rusted completely out. It was running on two cylinders and belching oil. You would get oil drops on you and your cloths when you used it. I hesitated buying a new seat as I was thinking of scrapping the tractor. My wife said "you can't get rid of that tractor you wanted to keep it for sentimental reasons" Well I know when not to argue with the wife.

So I just had the engine overhauled. The motor now runs very strong and starts quick. It pulled 22 hp on the dyno!

I have a new carburetor and generator I bought at central tractor when they were going out of business. I am considering going original. I am concerned that 6 volts may not be enough to start the tractor with the overbore cylinders. Plus I would have to redo the starter again.

The tractor is out being sandblasted right now.

Thanks for any and all advice.

As far as starting it with 6 volts, it shouldn't be any problem at all. I have a B (same engine as yours) with oversized, high compression pistons in it and it starts fine, even in winter, with a 10 year-old 6 volt battery.

Unless you had your starter specially rebuilt for 12 volts, you probably won't need to do anything to it to go back to 6 volts. Those starters don't care about polarity, and will work just fine on 6 or 12 volts.

This battery was purchased in the fall of 1994.
To be fair, it is probably in it's final year, but it hasn't yet failed to start the tractor.