[size=12]Hey Mudviper. Just saw this post. The tube your curious about is a vent. In later designs it was determined that the necessary venting action could be accomplished without it. As far as deleting the insulator goes, it is necessary for precisely the reason it is called an insulator. It and the two gaskets keep the heat in the bowl/main body section so the fuel in the bowl, when called for, is of a proper temperature to atomize correctly in the airstream going to the cylinders. Proper fuel temperature is also why there is a heat riser valve in the exhaust manifold. To quickly bring the fuel in the bowl up to a proper temperature. However, if stuck open, that heat will cause the fuel in the bowl to boil and flood the carburetor much as you have described.[/size][/b]