thats the base gasket between the carb and the intake manifold. replacing it will be essential, since your bike will start running too lean if its getting too much air and not enough fuel. thus, causing the bike to run hotter than it should. ill try to find a schematic for carb removal. it should be a simple fix it could be from the top of the carb as well and is just dripping down and hitting the hot engine block while its warming up inside? i noticed the change in performance on my bike w/non ethanol gas. more so in my old 68 chevelle! haha it does make a difference with carbureted engines.