Modern Vespa

OK so my 24.24 carb may be warped. I'm thinking of slapping the 20.20 back on. This is my P200.

The question is - if I'm overall satisfied with my jetting on the 24.24, how much, if any, should the main jet size shrink with the 20.20? On a Lambretta SH carb, only one or two jet sizes was my experience. So let's say my main is 125 right now (I run a SIP Road). How much, if any, should I expect to knock it back for the 20.20?

I'm assuming same idle jet, air corrector, and atomizer will work ok.

I run a 102 on my stock engine with 20/20. maybe youd be at a 105?

Yeah that's the part I never understood - there is a big gap between stock 20.20 jetting for the P200 and stock 24.24. So I'm really hoping someone has run both carbs on the same engine and can pipe up with their experience on what the engine actually wants (not worrying about emisisons passing, etc.).

I checked my notes, I had 107 with the go fast expansion chamber that was on it, just seems crazy to drop 15+ numbers.

I should have been more specific. That 20/20 is on a 150

Mine's 200 with stock cylinder. Thanks for clarifying.