Extremely high rpms on start.

So im still working on my '82 kz440 ltd. I've gone back to the stock airbox/cap thinking that would solve my high idle issue.....it hasn't. I replaced the carb boots to the engine thinking there was an air leak there, didn't fix anything. The problem is when I start the engine it revs up to 6000 rpm and will not come down. There is some backfiring and white smoke from both exhausts while it is running. Today there was also a very small amount of oil under the bike.....I have new plugs/wires, new throttle cable, I have the mixture screws out 2 turns. The only way that I can get the rpms to drop is to stuff pieces of shop towels in the filter cap. When I do that it idles at a smooth 1000 rpm but I cant give it any throttle without it dying.....I am just so lost at this point any help would be appreciated. 

Have you tried to run the bike with the throttle cable(s) disconnected?

During the work have you had the carbs apart and bench set the slides without ensuring that you idle screw was set mid point. Sounds like your slides are not being able to close sufficiently.
could also be caused by the throttle cables being poorly adjusted creating the same slide issue.

I have not tried that. Ill give it a try. Its really weird. The idle screw is all the way out, there is literally slack on the throttle cable. Even if I turn the mixture screws all the way in it still idles at 6k. The only thing that will bring it down is reducing air intake. 

I have no clue how to set the slides....I will do some research and see if I can figure it out. 

I just tried disconnecting the throttle cable, the issue persists. 

Are the vaccum ports on the carbs plugged?

 

One vacuum port is capped. The other goes to the petcock and I have it plugged off because I am just gravity feeding the cars at the moment. 

I just tested the slides on the bench with compressed air and they seem to be sliding with no leaks. I re-checked the air box and all boots for cracks and there is none. I got a brand new air filter in the cleaner cap, should I soak it in something?? Also is there supposed to be a filter inside the air box below the air cleaner cap? 

Here’s a manual. 

www.kzrider.com/modules/ServiceManuals/kz440.pdf
 

Your LH carb is a way out of sync and your sync adjustment need a fix. The washer and spring belongs under the butterfly accutator of the RH carb tab. Washer on top of the spring.

 

I didn't even notice that. Thank you! This probably won't fix the issue but never the less it needs to be fixed.