Another thing to check is the tank vent tube. Most people don't think about it, but I found out the hard way (at an $80 price tag, with the shop saying, "we can't find anything wrong"), that when that vent tube gets plugged or restricted, it can cause the gas to not flow out from the tank to the carbs, so it will just die. On mine, the vent tube is on the back right side of the tank, opposite the petcock. If you open the tank cap, start it, and it runs fine, then that is likely the culprit. Just remove it, and blow it out, and save yourself the $80 dollars. I think a bug crawled up in mine, and died there, with it's dead carcass restricting the air flow.