Hard to say what has happened. Maybe carrying it in the back seat of a car has damaged a pipe & gas has leaked out or not allowing it to stand for a while before running the motor has forced sludge up in to the pipes causing a blockage. Turning it upside down for two hours has to be the dumbest suggestion I have heard. it will not achieve anything. Time to bite the bullet & pay for someone to come & repair it.
George, December 2009