Sounds like your idle mixture is hosed. I'm not familiar with the TT engine so someone correct me if I'm wrong. Find the idle screw (usually opposite the carb from the main needle valve). I'd run it at the lowest throttle setting you can keep it running at and turn the idle mixture screw until it smooths out. Just like the needle valve, clockwise is lean, counter is rich. I wouldn't have a guess as to where you're at now so try one direction and go the other way if it gets worse.

Cary