Rapidly fluctuating vacuum on sync gauges

[DutchDaye]

1980 dohc came to me as non runner carbs in pieces got them all cleaned up and together. Bike starts but sync gauges are all 4 rapidly bouncing in wide arc. Make me think timing or valve adjustment. But I'm a harley guy haven't worked on a cb in more yrs than I care to remember. Any pointers in a direction would me much appreciated

 

[dirtdigger]

Gauges need to have dampers so you can slow down the bouncing.

 

[BAHNST]

FWIW i use this on twins, with the 4 pot adapter for the CB......

https://tecmate.com/carbmate/