Greetings:
Sorry for the mis-assigned quote, 4.
The chart The Bear posted has value to help us understand which carb feature does what. I'm pretty sure it's a Mikuni publication. I'm also pretty sure one can't apply
all of its assertions to any other carburetor.
Of this I am certain. On Bakaracer's advice, I've begun "Pre-tuning" my OKO 26's air screw before mounting up. It's within a very narrow range; 1.5 turns out for cooler mornings and 1.75 for the warmer afternoon ride home. Besides the palpable improvement in mid-throttle response, I've noticed that when I fail to turn it in that quarter-turn, my temps are about 25 degrees higher in the morning than when I do. (Admittedly the VDO gauge isn't the most accurate or easy-to-read instrument in the world...)
What I think is happening is that the air bleed regulates the idle mixture as suggested in the graph. I think it's also letting a trickle of air combine with the fuel in the Emulsion Tube tower, so the "fuel" joining the main flow in the venturi has a bit more air bubbles in it too. I'll be the first to admit I haven't examined the OKO carb's circuit schematics very closely. Also, what happens on the OKO may not be true for the PA.
As a side note, KyleBo sent me his
process and pics for modding the Pilot circuit, posted in Advanced Tech. Worth a look to anyone trying to BBK or Intake Mod a Spree/SB or any stock-carb scooter.