Got it going again, Same issue

You check pipe for obstructions?

That year doesn't have a power valve, does it?

For jetting, try going up or down several sizes on the main to get an idea of where you're at. You aren't going to seize it from just a quick blast through 3rd gear to see if it cleans out and runs well.

Is the coil "new" as in NOS

Dont fret, you are right there about to find the problem. You changed all the big things like stator and carb. Just brainstorming, is the filter new? (I left a rag in my new 250f airbox, the first 3 times I rode it I wanted to burn it because it was so slow). Air vent for the gas cap clear? Maybe find stock carb jetting and make sure it wasn't switched. Someone slow owned that bike or it wouldn't be so nice when you found it, and could have loaded the thing full of oil,make sure the pipe and silencer is clear like Big Al said. People in Wisconsin have has cheese in thier exhaust. Is the coil you have new or just from another bike? I have a stock coil you could try. I really like that bike. The 84 KX were the best looking production bikes ever

So you put the Keihin on it? Was it new?

What did you get a shock reserviour from? It looks good. Does the stock one have a bladder or a piston ? I had a trashed 250 shock I bought for the spring for my 125 and I saved the stock finned aluminum reserviour because it looked so cool

Assuming it's not the float as that effects all circuits.

If it's not running properly when the throttle is opened all the way up, the needle is not the correct jet to be worrying about. That's the main jet. Go pick up 150, 160, 180 & 190 mains. Try them all and keep in mind while testing that the main jet is a factor from 3/4 throttle and up. Yes, all the jets overlap a bit, but you're just trying to get it to run decent, not fine tune it.

I've had two bikes do this due to needle jet issues. One was actually the venturi that the needle jet goes down in, the part the main screws into. It had a groove worn in the side of it. Bike ran great at idle when you first started it but as soon as you opened it up once, it all went to crap. Ran fine wide open though.

The other the little keeper that goes over top of the needle that holds it in place in the slide was missing. Bike started and idled fine but when you opened it up it went all rich and bogged like crazy from then on. The needle was hanging open even when the slide was closed.

Oh yeah, had a CR85 cause considerable problems too. Owner had pulled the carb and it wouldn't run right after that. There was a little top hat looking brass piece that went in the carb before the venturi for the main/needle. That top hat had fallen out and was missing. Had to buy a new carb to figure that one out.

How about the reeds? If the bike has them?

as to be the cdi. Last night when i read this i thought you changed it. Unless im missing it that its stock. Unless you switched an original bad stator for another bad stator it has to be the black box. Even if it were one of the other things you had changed like jetting or a coil, you would see some kind of difference. But it has the original problem every time.. maybe check the wires where they bend and go right into the black box. Perhaps something is cracked or dry rotted.

I misunderstood your original post to mean that the previous owner rode it in the current, crappy state and just dealt with it.

I agree with Max- electrical.

Spider, I am going to agree with Max Power. My guess is ignition and it may be as simple as timing. I chased a problem for way to long thinking carb and center case leaks. Was a stator I had swapped. Both looked "identical" but were from two different years.

On the bright side, I won the village idiot of the year award for my sufferings.

Try putting a timing light on it and check the timing. Make sure you can see the advance as you rev the beast.

Regards

My Cagiva had a similar problem, seemed fine on the bottom but the more the rpm went up and by the time I hit 3rd gear or was WFO it would die. Ended up being the coil was bad

Spidermonkey, If the crankcase bore and top end compression are good then its probably the electrics,

Spider, I just looked up the stock jets and it shows a 340 main and 27.5 pilot. Based on the 160, I think you are way too lean. But why is the question.
https://www.rockymountainatvmc.com/oem-schematic/2

Have you ever put a timing light on the bike? It would eliminate the whole guessing game. Lining the marks is fine, but the timing light would tell you where it really is sparking. It also would allow you to see the advance is working properly.

Try to get a timing light on it and let us know what it shows.....

It has to be frustrating for you after all you have done. Dang, it's frustrating for me. I'm offering cheap advice to go spend money on a CDI and it wasn't the problem and I feel stupid. Sounds like you have done all there is to do. But it has to be something. Could the air filter somehow have gotten wierd from age? Did you change it. I like to install a freshie on old bikes just because i hate cleaning them. Maybe try pulling it and take a blast down the road. I would have bet my last dollar it was the stator or black box. If that's not it maybe try the old trick of running it in the dark to see if you can see an arc somewhere like you would on a old Ford Fairmont. We aren't looking for a cure for cancer here. It has to be something.

http://www.2wheelpros.com/oem-parts/kawasaki-rotor-21007-1129-part.html
Cheapest ive found
This is 270
Most were 311
Seems its unique to the 85. Perhaps other years would work but are a different weight

You need to pressure test the engine to make sure it's sealed up before swapping out other parts. Also, keep some NEW plugs on hand while tuning and clean them out with brake clean if they get wet. Also, if that's an off-the-shelf Keihin, they require alot of tuning, maybe even a new slide, to work right. You might be better off using the stock carb if it comes down to the carb being the issue.