cletis is right all though when the engine is warm the "Valve" is considered to be open. The weight will be at the lower position (open) when it is free to do so. The by-metal spring will overcome the weight when cold and "close" the valve. In either case the exhaust remains open. The exhaust air is simply deflected to the bottom of the carb. when cold.

I didn't do it, no one saw me do it, you can't prove anything! "Bart Simpson"