Re: 2004 Classic 60hp 3-cyl
They want the butterflies to stop a bit shy of full lock open. They could stick wide open and that would be a bad thing. Once they get within a few degrees of fully open, they are letting in all the air they can anyhow. Or put another way, the diameter of the shaft prevents a fully open butterfly to allow any more air through the throat anyhow. So if the butterfly is only opening to the point where it aligns with the outer diameter of the shaft, it's as wide open as it needs to be. More is irrelevant.
