I bought this sled at the beginning of the season last year with 1000 miles on it. It ran well initially, but began fouling plugs during the winter. This fall after getting it out of storage, I went though about 10 plugs (old but clean) before I got it to run on two cylinders. After running a minute or two, it fouled another one. So I decided it was time to go through the carbs. They were a little dirty but not too bad. I cleaned them thoroughly, checked float levels, etc. Put it all back together and it started right up, but only running on one (the right) cylinder. Tried a few more old plugs, but still only one cylinder. Went out and bought new plugs, and it has not fired once since. I have great spark (tried two sets of new plugs), compression is 125-130 in both cylinders, and I'm getting fuel. I can lay the plugs on the top of the head, crank it over, and flames will shut up a foot in the air. But it absolutely will not fire with the plugs in. I have a good inductive timing light, but don't know how to check the timing without the motor running (and no battery). Also seems unlikely that the timing would just go out. One friend thought maybe the crankcase is full of fuel. I have let it set for two days, and it still won't fire. It's in a heated garage. Any ideas????? Thanks! Also, this sled has the HAC (high altitude compensation thing) and about 1400 miles. My other sled is an Indy 400, which runs great.