That seems to be the real question here that a few (including Wolfie) have been asking recently.
At this point, we just need someone to simply test this out to see if it works.
Yes, it will work. Even though I have never had a Kaw petcock apart, I have had others. They are all simple devises that must necessarily act in the exact same manner. The exact same principals apply to vacuum/boost referenced fuel regulators.
I have not been inside a VN petcock, but this is what you will find.
Vacuum overcomes a spring (compresses), and pulls the diaphragm toward the vacuum side. In the middle of the diaphragm directly opposite the spring will be a protrusion/fuel obstruction. To eliminate vacuum control, remove the spring and shorten the protrusion on the opposite side of that spring. If the protrusion provides a 'seat', simply removing the spring/disconnecting the vacuum source will remove vacuum control. If the resulting fuel delivery is insufficient, find a spring with a slightly larger diameter than the protrusion and install it on the gas side of the diaphragm using the protrusion as the spring guide. You quite possibly could remove the spring and just turn the diaphragm around. Install it backwards.
You will now have reentered the 1970's, and must (for safety's sake) turn the petcock off anytime the engine is not going to run in the short term.
I may eventually do this to mine. HTH.
Edit. You could also just install a check valve in the vacuum source hose. This would maintain a constantly high vacuum to the petcock. Available at auto parts stores, these should cure virtually all issues. You would still have to constantly turn the petcock off when not in use.