If the float level is too high, gas will dribble out of the venturi when the engine is idling. Set the float as high as possible without gasoline dripping into the airflow at idle speed. If you could see a cross section of most carbs, the level of the liquid in the float chamber will be just slightly below the narrowest point in the carburetor body (the venturi) so just a slight increase in airflow above idle starts drawing fuel into the air stream. The higher the float level is, the richer the carb will run at any midrange to cruise RPM.
Jerry
