That little needle w nut is the idle mix adjustment.
And Mark is right this time, you need to adjust idle mixture, I'm betting it is too lean and misfiring.
I'm wishing folks would not go swapping jets around so much, esp when they can't get the very very basics (idle mix screw).
For my money put all the jets back stone stock, set idle mix, get tested, report back.
Emissions Help
Re: Emissions Help
I was changing jets as this is what was suggested the first time I had this problem. I didn't know about this screw as it was never mentioned and now that I am exploring I found it. I have put the jets back to what worked for the last three years and it seems this screw does very little for my issue. In fact I seem to be running worse now. I think it is time for a new carb. I may try the 34 ADF I have or just buy the 32/36 ADFA or whatever Vandor mentioned in another post. but I kow I will need studs to mount the carb I have.
Re: Emissions Help
The idle/low speed jet on these plug constantly. If idle mix screw is not affecting idle, and idle is poor, jet may be plugged.