Bit Of Advice Needed.

Don't know if it helps, Joe, but when I were a lad and carbs had throttle slides and bugger all air filtration, we would use lollipop sticks or long matches balanced under the slides, and then watched as the throttle was slowly opened to see which stick moved first and then the carbs could be adjusted as necessary. Because of where the fulcrum of the stick was in the intake, a very little movement of the slide would produce a much bigger effect on the other end of the stick, so it was pretty accurate.
Fuel/air mixture was another problem entirely.

 

Are you talking throttle stops or just the cable opening Joe?

 

Vacuum ports should be on the inlet manifold not carbs themselves. You can make your own manometer with plastic tube but use light oil rather than water for a more stable signal.

 

Joe, I suggest you have a look at the CB500 site here
http://cb500.forumotion.com/forum
Very helpful people even though the search function on the site isn't very good.
The watercooled CB500 - great wee bike by the way. I've had mine for years.