I know this thread is old but are you sure the vent for the gas tank isn't clogged? The running and dying within a few minutes sure sounds like the carbs aren't getting a steady stream of gas. It could be you are emptying the float bowls before they had a chance to refill. I've seen this happen on a snow thrower. Try running it without the cap on. Do you have a vaccuum actuated petcock? Check that too.