In the first place, the fuel level should not be that high. Make sure the vent hole is not plugged.

This should work – make sure the bowl gasket doesn’t catch on the float. . . 😉

the float should block off any excess fuel at the rim of the carb bowl base junction….. if the inlet needle is working ok. that is why the float must be level when you flip the carb’s upper half upside down see pic. from garry

if the carb fills up to the top …enough to spew gas out….. the float/inlet needle assembly is not doing its job and you need to find out why before plugging anything.

think of it as a toilet bowl float valve… if it is overflowing it is not working right

That passage goes straight to the bottom of the float bowl through the float bowl gasket. If the vent gets plugged, air trapped in the float bowl keeps the float from rising and any fuel pumped in goes past the high speed needle valve dribbles out the high speed nozzle and to the low speed needle valve through that passage. If that plug is missing, virtually everything pumped in will squirt out that hole.

have you done a blow test ?? air should not enter the carb bowl (body) when flipped upside down ….if the float and inlet needle are doing their job properly

with the carb right side up… air should enter the carb bowl (body) if you blow in the inlet