BS90 velocity stack/rejetting/airbox

[jbmjeff]

I am transplanting a BS90 motor in a chibi. I can relocate airbox/etc, but it would be a lot easier to just remove the carb sidecover and run a velocity stack with no airbox. 
has anyone rejetted a bs90 carb (mikuni vm17-18) with just a velocity stack? if so, what jets?

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[OldSwartout]

Sounds interesting.  The BS carbs don't have a shoulder on the inlet to clamp a velocity stack in the normal way, so that's something you'd have to work around.

[jbmjeff]

I can solve the inlet/velocity stack  problem with a grub screw/set screw.

the factory airbox is very restrictive, and I know that these bikes wont start/run well without some sort of airbox. I assume that someone has addressed the re-jetting  necessary when the carb is just just sucking air?