I usually just turn the top upside down, get the top of the float parallel with the gasket.
Be sure the float doesn't have gas inside, and the needle/seat are in good condition.
Could be rust and dirt coming down from the tank. Be sure the sediment bowl is clean and the screen is in place. I like to turn the fuel on before connecting the line, let it flush. The tiniest speck of rust can hold the needle valve open.