I agree nothing with webers is black and white but here is the article
"Idle jets operate from idle to 2500-3000rpms or so. Main jets are primarily from 2500-4500rpms, and Air jets affect the engine from 3500/4000 on up. "
http://www.aircooled.net/gnrlsite/re...es/jetting.htm
5th paragrah down.
It seems as if they are suggesting that the mains and the idle jets overlap. it also seems that the idle jet is at the taling end of the idle circuit at 2000 rpm and the mains need to start coming in to help the ending of the idle jet.
Could this be correct?