You ever seen a choke plate on a 4-cycle glow engine? It's just a little flapper on a spring. You put a finger on the flapper plate and it closes off the carb.

Maybe you could do the same thing with your carb. Use the carb mounting screws to hold a little ring on the face of the carb. Rig up a little metal or balsa flapper on a hinge and put a piece of rubber on it to make a seal. Rig it to a servo and a linkage.

Crude paint image:

How rude goldberg is that?


Edit:
Silversurfer beat me too it. I was gona tell you the same thing. [sm=lol.gif]