We can't move our needles on the U.S. spec carbs, they're "fixed" (only one clip slot). But, I really haven't found this a hindrance when tuning them. Normally, as you increase the main and pilot jet sizes, they bleed over into the midrange and eventually make it too rich. Then you would lean the needle clip setting a step to fix that. But with our U.S. spec BS34s coming so lean from the factory, this richening of the midrange from the bleed-over just seems to make it right.