Unfortunately, the O.D of the carb neck on these K&B's is 15.8mm. The venturi is in fact 8.5mm. I'd probably use the same size venturi, but I'd want better adjustability of the idle/midrange mixture than I do with the current carb. If I had the ability to machine small parts, I'd just make a new mixture disc and just move the spraybar orifice a little bit to have better adjustability of the midrange.