The first thing I looked for in the video was the Choke cam and roller. It appears that yours does NOT ride on the cam at idle and that's good !
If you can't find the problem while the carbs are on the bike, try this on the bench:
Depending on a few conditions there might be a coating of varnish on the cyl. side of the venturi. It is possible for this coating to become thick enough ( we're talking .000's ") to cause the throttle plates to get stuck on it, rather then against the actual Idle stop. Remove any staining/buildup regardless. Then apply several drops of Lacquer thinner to the Throttle shaft from the venturi side (4 places) with a SMALL artists paint brush. You just want to
introduce some fluid to the throttle shaft where it turns in the body.. Work the throttle and repeat 2-3 times. Then from the venturi side, blow with compressed air too force the fluid out that will have wicked into the shaft/body. Repeat until the fluid expelled by the compressed air is clean. This applies to the center part of the shaft, between the two venturi's, as well. You will not expose the seals to enough Lacquer thinner for
any concern. (Just don't soak the carbs in it over night
)
There should now be a discernible difference in how they close. When operating the throttle plates by hand, there should be a definitive feel of the plates closing tight within the venturi. Shine a light from one end. Viewing from the opposite end -there should be no light! You can leave the throttle shafts dry but smear a drop of oil on the exposed seal (1) and the other two under the dust-caps. The dust-caps pry off and reinstall easily. To hydrate the seal that's behind the control arm, just let a drop of oil run into the gap. Put 1 drop of machine oil on each link ball. Static sync. before they leave the bench. This can save a shit-load of time and frustration !
Check to ensure the throttle shaft arms are strait, flat and that the throttle arms to throttle shaft and the ball to arm are at 90 degrees/strait and parallel, respectively. Not suggesting you have bent them but not knowing the history: I've seen throttles arms bent noticeably from someone trying to pry off the link-rods without first loosening/separating the bodies to get that needed space. If you have disassembled the link-rods make certain that the little ball-race is positioned correctly in the bottom of each link-rod. A tiny drop of grease on this small piece will hold it in position when reassembling. Ensure the two internal pins are oriented with the correct end in the pressure spring. Obvious maybe, but still worth the mention. Ensure the throttle return springs on each carb are installed and functioning correctly. Two are wound the same with the other wound opposite ! This is a no-brainer - if they are correctly oriented they will close the throttle plates. Again, obvious; but if you've seen what I've seen....!
I'm confident this will solve the problem.
Hope this helps - scotch