Farmall Cub won't start (long post)

Just bought a 1948 Cub yesterday. I heard this tractor run in October 2010. It sounded good, although I know the motor has low compression. He told me he was selling it as non-running. I asked him why, because I had heard it run in October and he said because it has been sitting. When I picked it up, I brought a can of gas and a battery and I said to him, I'll drive it on the trailer instead of winching it. He said I don't think it's going to start...I don't know if I took the magneto out of this tractor. I really think he knew more than what he let on, but I don't think he thought it was serious. I have spark, but it seems to be intermittent. It backfires and seems to be out of time. I watched the video on how to time your Farmall Cub with a magneto, and followed the instructions perfectly, but I cannot get the mag to snap when I'm adjusting it like they did in the video or like it says in my book. The #1 piston is at top dead center and I did everything else right as in the video, and there is spark, but it just seems out of time. I had a mechanic friend look at it and it did the same for him. He seems to think the mag needs to be rebuilt, but I'm not so sure. Is it possible the govenor is out of time...it could have jumped a tooth?? I know this motor is tired, but like I said, I heard this tractor run in October and it was smooth as silk and not smoking, but did have low oil pressure. This Cub is in decent shape and has a sickle bar. I don't want to put hundreds and hundreds of dollars into it, but I don't want to have the mag rebuilt and then it still doesn't run and it's an internal motor issue. Any advice would be appreciated. Thanks.
PS: It will fart and run for a second at times, but it sounds out of time to me.

The mag is equipped with an impulse coupling. This device is a spring loaded trigger operated mag component that speeds up the mag internal magnet. At cranking speeds the magnet turns so slowly that the voltage it produces in the coil is not sufficient to make reliable spark. The mechanism locks at each cylinder location and as the engine turns, it winds the spring. when the engine gets to TDC, it triggers the release of the spring, allowing the magnet to leap faster for a fraction of a second. this makes nice fat spark. When it sparks the tractor starts, and the impulse system is disengaged the running tractor has all the speed it needs to make spark level voltage in the coil. It also advances the spark to full advance for running and work. It is set at TDC for the impulse to prevent backfiring and kickback when cranking manually or with a starter.

To fix yours, the impulse coupling needs to be cleaned out and lubed with a PTFE spray like Tri Flow. Set the #1 piston at TDC on the timing mark, with the mag rotor pointing to (or near the #1 plug wire terminal on the cap. If you carefully remove the mag, and do not move the engine, putting it back in is not an issue, if it ends up pointing at the same location.
Be careful with internal parts, there is internal timing marks on the rotor shaft as well. Best of luck. Jim