I
Norman,
I believe the prine function of that tube us to equalise the pressure in the float chamber with atmospheric. In that case fuel should certainly not come out of it unless the float chamber is filled to the brim and still accepting fuel.
That does imply a sticking float as previously suggested but it could also be a faulty needle valve or incorrect setting of the float level.
If the carb previuosly worked without floodiing, the float level is probably ok so is the needle valve stuck or jammed with debris?
B…..
Bernie