I modified mine a lot, ported and a cam, but before that even, the idle jet was too lean, go to a 22.5 or a 25 maybe. Also, when you bolt the carb onto the manifold, open the slide and look in there and make sure the bottom of the carb and the manifold are in alignment and smooth. I have to lift my carb up when I tighten it to make it right there. If there is a step it makes the idle signal poor and very hard to jet and generally runs like crap down low.