What fuel pump are you using? If it's the crankcase pulse diaphragm pump, no, it can't make too much pressure.
If you're using an electric pump, yes, it probably is too much. Those carbs are only designed for a few ounces of pressure.
Could be something is up with the float, level adjustment, or trash in the fuel.
Not sure about the seat... If it comes out I would assume it is replaceable.