First this is my personal opinion.
Vacuum gauges may not be the best choice. The the light weight oil I used in my balancer provides good pressure damping where vacuum gauges do not.
The vacuum of the running motor fluctuates every time the piston moves up and down. This causes the needle on a standard vacuum gauge to rapidly move up and down and look like a blur, making accurate adjustment of the throttle bodies about impossible.
The viscous liquid in the balancer does not bounce at all like the vacuum gauges, and makes very accurate adjustment pretty easy to do.
I have spent over 35 years trouble shooting, at one time I too was a amateur, what I learned is do it right the first time and share knowledge.
When things start to go wrong and they post a homemade manometer, the first thing to my mind is to ignore helping the poster, because they saw a post like yours and figured if he can do it for cheap, why not go that route myself, and that is where the problem starts.
I beg to differ, I did my own manometer originally, pick you fluid, you need restrictors as a mistake can easily suck your fluid into the TB, I know I did it. My Son got gauges, like you said the needles were all over the map. Then Smiley
on this forum showed me his gauges, these gauges are rock solid ( no fluid inside, stainless rods) . Carbtune Pro https://www.amazon.com/CARBTUNE-PRO-.../dp/B018UTHGPE
Check the manual what they state should be the proper vacuum setting, get that number from your homemade U tube.
What I am saying is something like adjusting the TPS on a 2007 Versys 650, moving it slightly left from the green mark, find the best performance and leave it, next when Invader asks what the setting is
yes you should have a good digital meter and the test harness. There is a thread on TPS https://www.kawasakiversys.com/forum...osition+sensor
So a brief explanation why go into detail,
you maybe as a mechanic or one that has done this a 100drd times could probably find a very simple and cheap means in any small town on a ride cross the country.Many of the members come here and to the How To forum for guidance then ask for a youtube link.
Something like myself, I could use the motorcycle battery and a signal light on my motorcycle as a continuity tester , however for a amateur I am going to recommend a voltmeter for testing electrical.And I am going to recommend CarbTune Pro also.https://www.amazon.com/CARBTUNE-PRO-.../dp/B018UTHGPE
So there are many posts for vacuum sync gauges, I have found something through Smiley
that is priced matching the excellence of the tool, there may be cheaper, but there is no fluid to worry about, and it is extremely accurate.