Ron,
"Generally," you will have a greater vacuum reading at idle than with throttle partially/fully open. Just a simple function of the throttle and choke plates being mostly closed when idling with the choke "off."
It also depends where you're vacuum source is...i.e. are you using "manifold" vacuum (under the throttle plate level of the carb) or "venturi" vacuum (between the throttle plates and choke plate on the carb)? Put simply, manifold is usually found at those little ports around the base plate of the carb, whereas venturi can be found at the little ports around the middle or top of the carb body.
I probably shouldn't be telling you any of this, I have
ZERO experience with these old carburators you folks use on the inliners. I'm basically just generalizing. Check out the vacuum link above...think I might just do that myself right now.
Regards,
Wannabe
P.S.
GREAT link, Ralphy! Thank you very much for sharing!
