Thanks for all of the advice! A few things I can add: I've drained the bowls multiple times, they are extremely clean, and the fuel in the tank is fresh, I did try spritzing the intake with starter fluid but it was a no go. Sounds like it's time to borrow a neighbor's timing light. One other thing to note is that if I leave the petcock in the open position, eventually fuel will start coming out of the drain tubes attached to the bowls. Is this contributing to the problem and is this supposed to happen? (floats set too low?)