Tractor Question

Do any of you guys have experience with tractors? My patience is about to wear thin with my old Ford Powermaster 861. For the longest time I had to give it more choke in order to run well the longer I worked it. Well guys about two weeks ago it just stalled out and wouldn't fire up. So I replaced the coil and adjusted the carb. That didn't work. I found some points that looked okay in my parts shed and gapped and replaced them. I set the timing with the help of a friend and it ran great. Well today I start plowing and about ten minutes in the same thing happened. I had to give it more choke to run smoothly. Unfortunately after a brief time it began running very rough and finally stalled out. Could my distributor be the issue? Are my points bad? HELP!!!