Idle hanging high if the idle has been reset to correct when engine HOT is almost always an air (vacuum) leak of some sort. You MUST have too much air getting into motor above the idle requirement, then pulling engine up higher is normal use and letting go of throttle makes the idle hang. Can be one carb off in sync, very common to leak at the head to carb manifolds even if you think they are in great shape. More rare but throttle cable with not enough slack in it, you must have a small amount of slack left with throttle 100% off before rolling it open pulls the butterflies open.
Very common on lesser quality older engines to have the idle set high enough to hang due to old engine needing more air just to keep turning over but not likely maybe in your case.
To tell if carb bank is the problem, with it off and in front of you at the same settings that hang idle high, look at the 4 butterflies from front of carbs and ALL must be virtually 100% closed and at the dead same spot. There is a small hole in bottom center way forward that feeds idle fuel (curb idle port) then a few holes further back ( off-idle transfer holes)that act like accelerator pumps as the throttle just begins to crack open, proper idle position will have the very front hole of those in the group to be either barely covered or EVER SO SLIGHTLY exposed, over half of hole showing is too much air crack there. All 4 need to be the same too, one off can hang the others and if vacuum synced to end up like that it's evidence of one cylinder not pulling to match the others. There is one other small hole forward of the butterfly and up on the right side a bit, the aircut vacuum port. The #2 carb will have another hole all to itself for supplying vacuum to the fuel demand valve on later models.
I personally bench sync to make all 4 butterflies barely cover the front hole there and all dead even. Often if rest of motor in good shape you are synced well enough to drive the bike pretty good then. If you have the first hole showing solid that is probably enough air to hang the idle.
In post #5 of this thread higher up 91octane in his third pic clearly shows a butterfly open way too far for idle, it shows the entire first hole and part of the second open there and would hang like no tomorrow. Would also be running rich as the hole amount exposed is feeding fuel once the butterfly opens past it. They are only to feed fuel instantly as soon as the butterfly cracks open, they keep mixture going to engine while the transition from pure idle to primary system is taking place, the accelerator pump hasn't begun to work yet due to shaft not moving far enough to activate its' check valve.
Aircuts leaking at diaphragm are a vacuum leak source too.
Most of the time it's the carb manifolds to head leaking.
Hope I haven't choked you there......................