Last week I was splitting wood and using my 2N to move the wood on a util trailer. With no warning the tractor quit running. Thought I was low on fuel so I added a couple of gal. Tractor would not start unless I had it at about 1/2 throttle and the choke all the way out. Would quickly die and I could not find a spot where the choke would keep it running. Nursed it back to the shed and get another worker to cont my wood moving. Today was a great day in MO - 75 degrees. Shorts and tee shirt. Spent about 3 hours on the 2N. Checked spark - good blue snappy jumps 3/16". check fuel flow thru the carb. Seems good: no water in gas. Removed air hose. Good suction. Tractor will start at mid throttle and run less than 3 sec before it dies. There is spark on all 4 cylinders when it quits. There is fuel in the carb when it quits. I removed the carb and replaced it with one from a running tractor. Same symptoms. I removed the dist cap and checked the rotor. Looked good. I ran out of daylight and will cont tomorrow but don't know where to start. Plan on doing a comp test and swapping the dist with one from a runner. Any other ideas. Sorry for the long post. Thanks for your ideas.