Klxster, you're correct on the requirement for "lack of turbulence" you mentioned for CV carbs, and that's why there were often weird fueling issues with those older inline fours I mentioned with CV carbs and those K&N individual filters. Air turbulence was too close to the carb's intake mouth. But when the airbox is still in place, and especially when the opening is still fully contained under the seat, you're not going to get influential turbulence.

I'm not doubting your findings that a lidless KLX will exhibit some fairly dramatic fueling issues that need to be addressed, but it's due to the relatively massive increase in intake air volume available compared to that tiny opening when stock. Then you add the requirement for the manufacturer to meet emissions, and you're dealing with a carb set up to perform with a tiny, muffled air intake and an obstructed exhaust.

I think it's also why the 34mm and 36mm pumper carbs are so popular when you start opening up the intake and exhaust on the 250...and especially increase displacement. I find the OEM CVK carb to be relatively lousy on the KLX. I had four KLR600/650's with the 40mm CVK, and they all responded quite well to a less restrictive airbox and exhaust with proper jetting. I don't think the 250 carb has as much latitude, but it's not a horrible carb either. And of course we're dealing with a fairly anemic level of power in its OEM condition with the 250.

But as I mentioned in my first thread on jetting, it's easy to get too wound up around the axle on this. The OEM CVK is more than capable of achieving a very adequate fueling performance with the aftermarket tweaks we often add like better exhaust and more intake airflow. Getting down to finite research and diagnosis is very satisfying and actually useful for perfection, but we're dealing with a KLX250 here.