Air gap adjustment, with the engine running, is by bending the rod. But this assumes the engine has enough vacuum to actually pull it open,lol. The screw you see hiding down there is for adjusting the fast-idle speed while on choke and specifically after it has been "tapped down"
Go back to the pic in post 51. You see that little tang where the choke coil anchors on? Attached to it is the vacuum pull-off piston.Engine vacuum is supposed to suck the piston down the barrel until it bottoms. This sets the initial air gap to spec. If your engine doesn't like it perhaps because of the timing, or T-port sync,or the float-level, or for whatever reason; then you get to adjust the gap, by bending the rod.
If the choke time cannot be made long enough with the existing heater element, then you have to reduce the voltage to it. But really, a little timing retard and a little more fuel in the low-speed circuit,usually gets the job done.
