Idling issue

[shedhappens]

Finally got the Stag back on the road after 12 years sitting in my late father-in-law's garage. Rebuilt carbs, steering rack, suspension, brakes, cooling system etc. Started first turn so well pleased. Still lots to do but its good enough to drive my daughter to her wedding as is her wish!
It's idling a bit high so went to adjust but noticed something that seems weird ... the intake vacuum appears to be holding the butterfly open and there's a gap to the idle screw. In the video you can see the linkage move when the engine is turned off and then sits against the screw.
Any thoughts? Is it just that the spring is weak maybe?

https://photos.app.goo.gl/oLMizbfT64u4cu1N9

[richardthestag]

Carb rods are set too short would be my guess looking at that. disconnect the carb rod between the two carbs and see if it still happens

[shedhappens]

I had disconnected the link to the other carb to isolate the issue.
When the engine is running there is a gap between the arm and the idle screw. When the engine stops the link moves against the screw. Which is why I said it seems almost as if the manifold vacuum is holding the throttle open somehow, very strange.