Fuel enters the float bowl from the fuel pump and through the inlet strainer - If the strainer is missing then be sure you have an external fuel filter in-line between the fuel pump and the carburetor. The strainer is used to keep the inlet needle & seat clear of any particles. It doesn't take much to obstruct the needle from closing, thus causing flooding.
As the gas level drops so does the float. As the float drops, then needle opens to allow more fuel to enter the float bowl. When adjusting the float do not put any pressure on the needle. They are easily damaged.
Dirt in the needle & seat is probably the number one cause of flooding. To test turn the carburetor upside down and blow through the fuel inlet. You only needs 4 lbs of pressure. The needle should hold pressure.