After Setting in a hot enclosed trailer, my Cub trimmer builds alot of pressure in the fuel tank. Actually all trimmers and blowers do the same. The Cub seems to flood. When I go to start it, the engine is full of fuel. Have to clear. Is this a bad carb problem, or should I loosen the fuel caps? Hate to drive around with the caps loose. The trimmer runs great after clearing all the fuel. Thanks.