Check the needle and seat, make sure that the tip of the needle is not cracked or distorted in any way, also check the fitment of the needle in the seat, there should be minimal side play of the needle inside the seat. Chack the float arm level as well, when holding the carb upside down with the bowl removed the float arm should be slightly higher than level with the gasket surface of the carb body. Check the folat arm pin as well, if it has worn considerably where the arm rides on it then the pin should be replaced. If there is fuel coming out of the vent lines then the float valve is not closing as it should be.