I know it's not the exhaust. What I said was "If the exhaust is cracked, then you've definitely wrecked it hard enough to cause an air leak somewhere so that is a possibility." Personally, I think you've got it way out of tune and you need to fool with it longer than 20 minutes. I had the same issue with a Savage, thought I had a bad glow plug, changed coudln't get it to fire, etc... I kept fooling with it and finally got the tune close enough for it to crank right up. Moral of the story, it took a few hours for me to get it. As soon as it tried to turn over I knew that it was a tuning issue. Tuned it once it was running, and the next time I started it, it started up in about 10 seconds.