There is only one reason a bing will leak THE FUEL LEVEL IS TO HIGH therefore overflows. There are several reasons for this and the most commonly overlooked reason is dirty seat ( get an inline filter and clean the damn seat ) TEST IT OFF THE PED.... bowl off and upright gently blow through the fuel supply inlet and feel the air going through the valve now lift the float and flow should completely stop.
Are you using pump gas? Ethanol content makes gas lighter.
Remove float from carb and test if it really floats in your premix.
I had a sinker once and it caused a leak
Also a leaker will cause richer/incorrect jetting due to excessive fuel height in the bowl