I get PTSD every time the 2CV has a hiccup. I have had plenty enough of carb issues to last me a lifetime.
You may think you know how the carburettor works; you've studied diagrams, watched training videos, and you're confident you understand it. You don't. The carburettor is the product of 40% engineering, 10% prayer and 50% absolute witchcraft.
As mentioned above my 2CV (and friends Ami 8) was an absolute nightmare, and it has one of the simplest carbs going. Both cars developed running issues that couldn't be traced even by people with many many years of experience of 2CVs. Rebuilding them, ultrasonic cleaning, checking for air leaks, even chasing faults round the ignition system, both cars were only sorted by replacing the carburettor. It only has an idle mixture adjustment, a throttle stop screw and a screw to adjust the closed position of the secondary butterfly. The jets alone control the running mixtures. The fault must have been one of the areas I listed above, but nobody could find it in either case.
By the time you'd have read this far, a computer would have probably told you Misfire Cylinder 3 and you'd have found a knackered injector.
If the above makes no sense, it is early and I'm ill and trying to talk about carbs is a bad idea.
Oh yeah, it's hard to miss coolant peeing out of the side of your engine, haha.