The needle valve adds more fuel as you turn it out. It only effects idle, once the throttle is open just a little the main circuit of the carb takes over. Try giving it a few more turns out, go till you can tell the engine is running rough or you smell fuel in the exhaust. Once you find that point, go in till it starts to die or stumble, then back it out till it smooths out but not so far it over fuels. 2 to 2 1/2 is about right for most carbs, the fuel quality can effect it (ethanol).
Joe
