Leaf Blowers

I have a 560BFS blower. It does not stay running. I start it, and it will run for 20 seconds as long as there is gas from the bulb. After that, it sputters and dies. If I try to open the chock, or increase the throttle, it dies.

I have taken apart the carburetor, changed sparked plugs, bought the $32 gasket kit and replaced all the gaskets, made sure the hoses are clean, and still the same problem.

Unit is a year old.

What could this be?

Thanks!