| Well its definatley not the manifold. I managed to jam the old sha rep carb on, (even with a broken attachment) and it runs like a dream. The current main jet has 78 stamped into it. Slowly opening up the throttle will maintain idle speed even tho by then you are bypassing the idle jet. Maybe the tube that runs up through the bore is stuffed or blocked so opening it up is not helping because its running soley through the idle jet and opening the throttle especially with the choke off is then giving it way too much air.
Why would an allegedly high quality italian made carbie be shipped with A: a blockage or B: a jet that is too small for even the smallest of engines? | 
