I skimmed the thread. Maybe I missed something. But, 069A carbs were tuned for a stock engine , the stock F muffler, and the stock air filter. If any of those things change, the carbs will never deliver proper fuel mixtures with the stock tuning parts and settings.
The pilot air screws set the throttle response off idle under load. )More about this later) It will run rather rich at idle, but not so much as to black foul spark plugs.
You need a dyno or a test track to find out what jets, slide needles, and setting work best for your newly engineered set up.
First verify fuel level in the carbs using clear tube test. Too high level will soot up spark plugs. 2-3mm below float seal seam.
If you won't take it to a dyno to get a fuel map print out, you will need to learn to read spark plug tips. Find a test drive area, stop the motor and put in fresh clean spark plugs, while the engine is at operating temp. Get on the bike and with the throttle wide open run through the gears to top speed. Hit kill switch and pull in clutch, coast to stop and remove spark plugs. The deposit patterns will tell you if you need larger or smaller main jets. If the tip insulators are light brown going whiteish, the main is good size. Going dark, too rich, full white too lean.
Now you need to set the needles. Mark your throttle so you know where half throttle is. Again with clean plugs, Start up and run through the gears using only half throttle to get color on your plugs. Still looking for light tan going white. Sooty, drop needle lower, too white, raise needle.
What remains is to determine if the needle taper is good. With the slide set for best half throttle, now use clean plug to test 3/4 throttle position operation. at end of run plug the plugs and read deposit patterns. If still tan going white, your needle taper is likely good. If rich or lean deposits show, you need different taper needles. Try ones from 022A, or 627b carbs. Repeat finding the needle position with the half throttle plug chop test. With luck your 3/4 and 1/4 throttle will keep your plug deposits good.
When/if you get success to this point, now set the air bleed pilot screws. Get the bike moving and put it in top gear, so the engine will get full load. Open the throttle suddenly to half way. If the engine wheezes and quits, then resumes with throttle return, the idle mixture is too lean, turn in the screws a bit at a time, until the bike picks up reliably, if not powerfully. If you can whack the throttle full open and the engine picks up, the idle is too rich and the air screws should be turned outwards to lean it. A too rich mixture will foul spark plug during prolonged idle, leading to misfires and burbling recovery with throttle changes, as the plugs heat and clear themselves.
Good luck!
