Perhaps fuel is dripping out of the venturi after turning the engine off.
You are probably flooding (getting too much fuel in the bowl).
Test the fuel pump to be sure it isn’t putting out too much pressure. Check your motors manual for the specification, but probably around 2.5 – 3lbs.
Make sure the needle & seat has the gasket installed and that it isn’t damaged in some way.
Make sure the old needle & seat gasket is removed. Any problem with the gasket would allow fuel to flow around the seat.
Test the brass float – heat up water and immerse the float. Any bubbles indicates a leak. You should not hear any liquid when shaking the float.
Make sure the float isn’t sticking when moving it up and down. A worn float pin would do this. The needle may have been damaged when installing. They are easily damaged. With the float up and the needle closed see if you can blow through the needle & seat. Look at the needle to see if there are any marks on the needle.
Be sure that the main discharge nozzle in the throat is gasketed and tightened.
Be sure that the float has no gasoline in it.
Be sure that the float lever is contacting the needle end squarely.
Be sure that the float hinge is not loose around the float pin (tighten with pliers if so).
Be sure that nothing is interfering with the float closing completely when the lid is installed.
Check the bowl vent to make sure it isn’t plugged.
#12 is the float retainer and it is spring loaded. Sits on top of the float and when the top is installed it is pressed down on the retainer. This keeps the float from moving at the hinge. You will want to make sure this retainer hasn’t been bent to where the top isn’t pressing it down.