They always weep a little bit around the gasket, but certainly shouldn't "overflow" unless the float needle isn't shutting off fuel flow.
Easiest way by far to check this is to remove the bowl with the carbs mounted on the bike, and turn on the gas. Set the tang for the fuel to shut off when the float seam is parallel to the carb body, as mentioned previously. You'll be able to see right away if it shuts off or not.
Let some fuel run through for a few seconds to "flush out" the needle seat.