First, set the high speed valve and then idle back. Start with the airbleed fully closed (running rich) then slowly open it (CW rotation) while monitoring engine RPM. At some point, the RPM will increase a bit. At that point you are close to the desired value. If opening it more (leaning it out) causes the engine to speed up and die, you've gone to far. If that happens, close it up until the RPM falls a small amount. There is some interaction between the high and low. Reset the high end for max RPM and repeat the low end adjustment. Depending on fuel, altitude and plug, you may have to enlarge the airbleed hole with a small drill to get the necessary idle, just go slow and do not overdo it.