I'm working on a 5 horsepower Briggs & Stratton engine. With a standard small engine carburetor I replaced my needle and seat with part number 39818 8 It seems to work fine with the bowl off. When I hold the carburetor as it would be on the engine. The needle drops down and I can blow air through. When I tilt it upside down. The float goes up and shuts off the air flow. However When I put the bowl on the carburetor. The bulb shuts off the air flow and I can't blow any air through. The gas line Does anyone know what the problem is?