I'm trying to get this Polini PWK 28 to play nice with the Malossi Sport 221. It does to varying degrees but I have difficulty working out whether it feels rich or lean.
I started out trying to follow this guide - http://www.shiny-red.net/guides/keihin-carburetor-jetting/ - and set the idle by the method they suggest. I ended up with a 48.
I had this carb fitted to the 177 for a bit, until the big end bearings felt they'd be happier without the restriction of the conrod. So now I've moved it to the 221. SDJohn suggested I start with a H needle (I have 3) and try the 30-hole atomiser... I thought I'd give it a go and see how it felt. It had a 122 main jet in there from the 177, it actually ran pretty well except for a patch in the 4-5000 area where it gurgled a bit. A 5 kilometre 100km/h run showed temps around 320f near the end, maybe they would keep climbing if I went further? Also I feel like 122 is pretty small, when I had an SI fitted to the same motor I was running a 155.
I looked for a richer main and the only one I had with me at the time was a 132 so i gave it a go. Quite similar but the gurgling area was now much broader.
I took it home and tried the 20-hole atomiser. Felt better at very low revs but very choppy until it gets up to the main.
So you can see I'm all over the place. I did follow SDJohn's thread (all 30-something pages) but the jetting advice never made much sense to me. I feel like what I need is a system. The link above has suggestions for individual carb bits, but the whole thing is based on the premise that the carb you buy is already pretty close to right.
What would be really nice is a guide that takes it step-by-step, but complete so you know where you're heading.