Ive been working on three TW's in the last few months. All of them I had to go through the carb. I have found that these carbs are Very sensitive to the airbox and filter.. If you have a disappearing or dried out air filter or any air leak behind the carb, it will run lean. Obviously a carb boot leak will cause a problem as well. One of the TW's i got had no air filter because it had disintegrated over time. It popped and surged and was lean. A newly oiled air cleaner fixed that problem. My 89 TW would run perfect unless you held it at 60 plus for a minute or two and it would die as if starving for fuel. That turned out to be a clogged inlet screen on the float valve. Seems both the petcock screens and the float inlet screen will gum up over time. It would let enough fuel in if the demand wasnt too much, but wide open for any length and it was too restricted to keep the bowl full. All three of mine have the stock 116 main and no washers and run fine. None of them surge or run lean on the main. They will all hit 70 plus on the speed and have a tan colored plug. But if you take out the restriction of the air filter and box and they will lean out with a an accompanying hot exhaust and white plug. Anyway, Ive determined that if you have it right, a TW will idle low and smooth and you can touch the front exhaust guard for at least 8 seconds with your finger. If you touch the guard on your exhaust and you cant hold your finger on it for a few seconds, you are probably lean. I could touch mine at idle and after a sustained top speed run for at least eight seconds. Another thing I noticed is that if you have the slide up too much on the idle screw, it causes a surge at idle because apparently there isnt enough vacuum to pull the low/ pilot thru, it is easy to turn up the idle screw, which raises the slide, too high without the idle going up. I would turn it down until it almost died and then back up a bit. This results, assuming your low jet and pilot circuit are clean and your air filter is in, in a very smooth idle without any miss or hiccup.