Could be loose slides...but I bet it is still the correct adj on the air bleed screws.
Is the throttle, from full shut, to 1/8 open, absolutely free of "dead" spots, a place where the engine just doesn't run quite right and ran better/faster at the point it was a bit less open? I mean, is the increase in revs a smooth/gradual thing? No places where it wants to sort of die...between a closed throttle and giving it gas? I had to play with mine. Eventually found one carb out of sync with the other (Slides not same height ), and at startup, cold motor, I had to slowly increase the motor speed, and when the dead spot was there, hold that place and fiddle with the air screw till the motor ran right and the dead spot was gone. Had to do it more than a couple of times to get it right. Listen/feel the blowing out of the exhaust pipe, note which side is guilty and fool with that side only. Carried a small screw driver too around for awhile too, and listened which pipe did it downhill, and tweak only that side on the side of the road at the bottom of the hill.
All popping gone now, though, and a nice gradual throttle response, which makes shifting much easier without having to mentally take into account the dead spot and dying motor. Only other popping problem has been the nice new gas taps, which starved the motor so much for gasoline, that the motor popped downhill too...got new taps on it????
