The newer Briggs carbs had a bad habit of leaking when sitting, the bad thing is that the excess fuel would leak into the crankcase and foul the
engine oil, so check that, then you would replace the carb bowl gasket and inlet needle, polish the needle with a q-tip and baking soda while apart,
and re-assemble, then put in an in-line fuel shutoff, to use when the mower sits in the garage.
Fish