Ken---I may be coming in late on this one, but just in case...Use
penetrating oil down in the air valve, where the adjustment screw
resides. In stubborn cases, lacquer thinner may be necessary to break a
possible varnish-type stickiness. You may have to invert the air valve
to allow penetration around the needle sleeve and the valve body.
Put penetrant in the threaded hole where the set screw was that you
removed, for a good shot at this area.
On the adjustable needle type carburetor, lhe purpose of the
spring-loaded screw is to keep the needle&sleeve from turning, during
needle height adjustment.
There is about three full turns of adjustment for the needle movement.
If you go CCW too far (lean), disengagement will take place between the
adjustment screw and the threaded bushing.
Dick
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