Getting in on this a little late so forgive me if I have missed something...  If you are having problem with gas dripping from carb when the engine is sitting (like over night) Then the fix is to install/or replace the gas shutoff valve between the gas tank and the carb... Or maybe the gas tank vent is plugged???? Going way back here, I was told the B&S told all the EOM's to install shutoff valves but they refused to do it because of cost.