The motor seems to have the float's needle valve in bad shape or probably too much gunk built already there. The needle doesn't close properly against the seat and spills fuel out the upper carb.
It's faster and cheaper to simple clean the needle's valve seat for a perfect marriage between both provided that the needle it's still sharp pointy. The OP has not mentioned whatsoever which HP motor/brand that might be ? In some motors can install a new seat in others nope....
