So does that mean that at some point the "dial-a-jet" becomes ineffective? I'm not questioning you're understanding... you tune airplanes, I tune mopeds... I just want to understand better.
It makes sense that the diffuser isn't very effective at idle because there isn't enough air flow to pull the fuel through the line and atomize it... but I don't understand why it stops working at WOT. Is there a "peak" output of the diffuser? Do you think since these carbs are smaller, maybe they wouldn't max out the fuel flow?
I'm asking all these questions based on simple logic. I don't know anything about fluid dynamics or anything and I certainly don't tune airplanes (props, no pun intended, to you).
Also... just out of curiosity... if there are any write ups, pics or guides to fabbing adjustable needles... that would be just fantastically interesting.