Hi Yorchie, I have fitted quite a few of the new 29 carbs to Comets, Shadows and Rapides. They seem to run lean off idle and you need to use the choke slide for quite a while until the engine warms, this i have found is mostly due to the number 4 slide they come with standard......perhaps this is due to the nature of the fuel we have to use these days. A number 3 slide will be on the rich side, so ideally you need a number 3 1/2 which are available from time to time....otherwise i simply machine 30 thou off the base of a number 4 slide, and this works very well. Run the needle in the middle groove to start with, with the standard 106 needle jet, and a 200 main jet is normal on a Comet.....finally, try and fit an air cleaner, as this will save engine wear and also the slide in the carb itself. The idle mixture will be correct with the screw approximately 1 to 1 1/4 turns out after being carefully wound fully in, this on a warm engine. All Vincent's look much better with their original carbs, and they run well on them too.....But thats just my oppinion. Cheers and good luck........Greg.