I had the same problem. Took the carb apart, rethreaded it, reassembled it and it leaked like a mother. Took it to pieces again, reassembled...did it twice more and then...TOOK IT OFF, HELD IT BY THE FUEL INTAKE LINE AND SWUNG IT AS HARD AS I COULD AGAINST A CONCRETE WALL...
...THEN I WENT AND BOUGHT A BRAND NEW DEMON, INSTALLED THAT AND FUNNILY ENOUGH, THE PROBLEM WENT AWAY...COMPLETELY!
Glyn