Denatured alcohol or HEET is what we use up north here... the water in the gas happens every year usually un the fall up here. I had the same prob last year till I dumped the old gas, dried out the tank, and ran a few cans of HEET thru it. You might wanna try about 3 cans first, its only about $2 each can. That way if it works, you don't have to drop the tank.
***--- Wrecking Crew member ---***
"I've prolly been around longer than you think"