I kind of like tweaking the jetting on my Vision since it's so easy to do.
I live in S. FL where it's hot and humid in the summer and I noticed the bike running slightly rich probably from the air characteristics compared to the Winter when the jetting was much better because of cooler and drier air.
So anyway, I was running 120 MAJ's up top and I picked up some 122.5's and 125's just to have on hand. I tried the 122'5's on the MAJ and with 3-4 threads showing on the accelerator pump and it's pretty good. I'm running stock main jets, pilots and pilot screws 3.5 turns out. Flap is on the airbox and it has a Keyster kit.
I'd say even with the 120's it ran pretty good and the richness was hard to detect under most conditions. The 122'5's seem a bit better for the time being, but as always I'm always listening to the engine! :)
BTW- Niche Cycle on Ebay is quick and cheap on the jets.
I think you're on to something here. I don't have humidity, but I've noticed that my fuel economy goes way down when I'm riding in 90°+ days, versus days when the temperatures are in the 70's or 80's. I think that the temperature compensation for these carbs isn't as good as, say, the carbs on my Ninja. In temps over 90°, I also have to be very careful to keep the bike from stalling at idle, which is never a problem in the cool of the morning.
Hmmm, I with the lack of accurate temperature compensation, I wonder of rejetting might not leave me too lean in the mornings? I have a feeling that Oregon mornings are a lot cooler than Florida mornings. This morning was 54°, for example. (The only part of Florida I lived in was Pensacola and Gulf Breeze, and in the summer I woke up wondering if it would ever cool off again. ;D For an Oregon boy, that was mighty hot. Swimming in the Gulf after work was mighty nice, though.)
Scott