Bike will not rev past 4000 rpm

My 82 kz440 is finally idling fine but when I give it throttle in neutral it will first hesitate to rev up, then once it does it will only go up to 4000 rpm and sputter until it finally dies.....I rode it around the block the other day and it would do the same thing in gear....I have throughly cleaned the carbs more than once, its got the stock air box, element, and new filter, the spark plugs and wires are new, it will start every time you hit the button no problem. One thing that happened tonight is that my left side cylinder didn't seem to be firing, I think this because the left pipe was much colder than the right pipe......I have the fuel/air screws turned out 2 turns each....Any help would be appreciated. Thanks in advance. 

Did you remove the pilot jets and bleed pipes from the carbs and hold them up to a light to make sure the tiny passages are open?  Remove the pilot screws and squirt carb spray though watching it come out in both the carb throat passages and in the pilot jet?

Yes I did that, I've had these carbs apart more than I'd like to admit. They are incredibly clean, through every hole and every nook and cranny. 

Do you have spark on both cylinders?

Yes, I had spark on both cylinders, the really weird thing thats tripping me up is that yesterday both cylinders were firing just fine. 

Check your timing advance. If ignition timing does not increase with rpm, that can cause this problem.

In the owners manual it has options for dynamic and static timing....on the kz440 D belt drive it is static I believe.....im having a hard time figuring out how to test the timing....im not sure I understand how to do it. From what I've been reading that sounds like thats the issue. Quick question tho, on the fuel/air mixture screws on top of the carbs by the diaphram, turning them in riches and out leans, is that correct or is it the other way?

No eBay APP ID and/or Cert ID defined in Kunena configurationThis e-bay image is a pic of the timing advance mechanism, right side of cylinder head. Make sure the weights are free to swing open as the unit spins.