A Walbro carb that won't draw fuel has a leak somewhere between the cylinder pulse hole and the carb body..If there are no leaks or restrictions the carb will pump fuel at least 4 feet straight up....Take the back cover (one screw) off and crank the engine, you should be able to feel a small pulse at the hole near the base of the carb..Be sure the diaphragm is against the carb body with the gasket on top..On the other side (4 screws) the gasket goes against the carb with the diaphragm on top..The inlet needle lever on that side should be flush with the floor of the cavity right next to the lever....Spark gap has no effect on the running of the engine unless it's too small.....