21-06-2022, 08:35 AM
In my amateurish view on the world, I have always thought that a larger carburettor may not give better performance. I have always imagined that a smaller 'throat' will generate a higher speed of airflow, thus giving a greater charge to each cylinder. There may be other advantages as well as a result of greater mix of air and petrol. I run 1" OM's (or are they 7/8", I'm never quite sure which bit you measure) and they run fine with good performance and econony. Noting Ian's comments, yes a selection of needles is required. The Minty Lamb web site is helpful here (http://www.mintylamb.co.uk/suneedle/) for assessing needle choice and comparison. If you wnat to get it spot on, however, the only real answer is a session on a rolling road. I had a Riley Nine once that when I first put it on the Rolling road, gave 31bhp at the rear wheels. An hour and a half later, it was giving 42bhp with careful needle choice etc... Best £150 I ever spent...