The AFM screw I'm talking about is the screw under the little rubber cap on top of the air box. Forgive me if I misnamed it.
I recently bought a '94 K75S with 9,000 miles on it, yes Nine Thousand, for $300. It was one of those bikes they used for filming movies and marathons, like Boston Marathon, or Spike Lees Klansman, trailered to and from events. From what I've been told the bike was only ridden by contracted California state highway patrol, and all maintenance done at dealerships. I'm converting it to one of those cafe/scrambler monsters.
I've been having issues with my bike running rich and went on a search to find the culprit. All fuel lines replaced, Intake boots between plenum and TB's replaced, vacuum lines replaced, Crank Hose replaced, all filters changed, oil changed, clutch properly adjusted with proper free-play, TPS adjusted. I've ruled out Fuel Pump and Fuel Pressure regulator for now, since there's 9K miles on the bike, and last time it was inspected was 2016, and it was supposedly serviced regularly at BMW dealerships.
When I first got the bike, it hesitated really bad when quickly snapping the throttle, even just died out sometimes. Idle was all over the place, I read all the forum posts where people were having that hesitation symptom and fixed things accordingly; TB boots were cracked, fuel lines cracked, Crank hose cracked.
Now it does not die out anymore, however it may unless it's fully warmed up. The other day I adjusted the Brass idle screws on TB's with vacuum gauges to get my idle proper. Today I looked at the AFM screw I mentioned above because when I hit the starter button while the bike was running, RPM's dropped. It was 1/4 Counter-clock wise turns from fully clockwise. AKA i screwed it 1/4 CW till it bottomed out.
I then progressively unscrewed 1/4 turn at a time until RPM's stayed the same when I hit the green starter button. I ended up with 3-3.5 CCW turns from fully bottomed out.
Fully warmed up it idles nicely at 1000-1100 RPM's, but still chugs-clunkers a tad when I crank the throttle off idle, and first gear feels underwhelming compared to the other gears; First Doesn't nearly pull as hard as second or third.
My question currently is how far out is that screw supposed to be? If there's anything else in my description that peeks your interest, I'd love to hear it.
Pics of before and current attached.