Regarding Mikuni 6-series needles, I have always wondered, " how much of the needle straight section is still available after the idle position of the slide" so I measured it. Mikuni quote a distance to the start of the taper for all their needles, but, how does that relate to throttle application?
These measurements were taken on my VM38 with right side idle adjuster (my left side idle adjuster measures differently, turns out it's an OEM Kawa slide.) I guess there is a bit of variation between the various models of VM carbs, especially when it comes to Chinese carbs, my Chinese carbs measured way different.
I took the measurements with the slide at 1.00mm from totally bottomed-out, my bike had the idle running sweet at .9mm but I've had some bikes that had the slide raised about 2.0mm at idle, although I think the idle mixture too rich and necessitated the extra air from a higher slide?
![](https://i.postimg.cc/kgnfNs3z/Mikuni-taper-starts.jpg)