Gas Quality...
Andrew - Today's reformulated gas is not as durable as the gasolines of 20 years ago. From what I have read and seen, it will actually go bad rather quickly, and weak gas could cause what you describe. So could several other things, as the other responses have mentioned. Here is what I would do. Completely remove all of the old gas from your tank. Siphon it or use a pump approved for pumping gasoline. I use one of those hoses that is inteneded for outboards. It has an inline squeeze ball that pumps gas when you squeeze it. Once you get the gas going, it will allow a siphon. Make sure you get the tank dry to the bone. This will require lots of ventilation. If you fail to ventilate the cabin, you will suffer, believe me. You could even die if the fumes are heavy enough. This, of course, is a minor concern next to the fact that you need to make sure that there are no sparks in the cabin, etc. Allow the tank to dry for a few days if you can.Once you are done, refill the tank with about 5 gallons of fresh 93 octane gas. Dump in some fuel cleaner as well. If this fixes the problem, you are all set. If not, get out your troubleshooting hat.If you don't have one yet, install a good fuel filter - it will pay for itself quickly. I once had a symptom just like yours - turned out I had a slightly clogged fuel filter. I changed it and all was well.Good Luck -Rob