Sounds like the pilots jets are blocked or air screws ports are blocked. I'd pull them out and look close at the pilots.Also, look at the bowls for corrosion. If there is oxidation clean all the white oxidation out of the bowls. Little bits can break off and jam the piots in a few mins. I'd also pull out the air screws and make sure you have the spring, washer and o-ring on each carb. While they're out blow some carb cleaner through the ports on the pilots and air ports. The new ethanol gas is very corrosive and can reak havic with your delicate fuel systems.
Good Luck
