Motorcycle Repair: CX500 throttle response problem, air filter element, air screws

Question
I hope you can give me some advice with a persistent , what I think is a carb, problem on my 1980 CX500A  (UK model) of which I am the FIRST owner.  
When I open the throttle smoothly and gradually the engine revs up and goes through the gears without any problem and in no time the bike is able to reach 150-160 km/hr and able to go further  .  At full open throttle it hesitates a little as well .
At say 100 km/hr in 4th or 5th and flip the throttle open for an overtaking manoevre the engine starts hesitating and the bike actually slows down and what feels like misfiring and the only way to overcome this is to close the throttle again and open it slowly.  Only then it will accelerate further.
When in idle I open the throttle slowly the engine zooms quickly to red line, although it feels like there is a flat spot during the acceleration around 4000 rpm.  But when I flip the throttle open very fast the engine does not go higher than 4-5000 rpm and runs terrible and sounds like it misfires or only runs on 1 cylinder or so.  
Here is what I have done so far:
-changed spark plugs;
-checked valve lash (was good)
-changed air filter element
-replaced the spark plug caps -cleaned carbs by removing them from the engine , opening them and blowiing out all passages and jets with compressed air; I can't see anything unusual inside the carbs; I did not check the small enrichment valve/diaphragm as described in your article
-I adjusted the air screws below the carbs and idle is very smooth and there is no (more) popping on overrun

 I have never separated the carbs from their bracket so original factory adjustment should  still be pretty much intact.

The engine behaviour during the rapid throttle opening as described above is very similar to the way it behaves when running out of fuel.  Yet, fuel flow to the carbs from the tank is full flow when I take the hose from the inlet pipe.

Hope you can help me shed light on this problem.

Thank you  

Answer
Hi Bastiaan.

The carbs could be overdue for synchronization, so make sure that they are correct.  Blowing out the carbs will not clean them.  Clean them with carb cleaner, because something is sticking and blowing them out will not clean up any build-up in them.

Start with that and let me know what you find.
Good luck and ride safe.
FALCON