I take a 2-56 socket screw, carefully grind off the threads on the last 1/8-3/16" and stick it in the little hole on the knurled knob on the needle adjuster and tighten the set screw. If it's way down inside a cowl, I make a guide of brass tubing that the hex wrench just slides through, and mount it on a stand-off, lined up with the adjuster and the hole in the cowl, with just enough clearance that it doesn't touch either. All you have to do is stick the hex driver in the hole, the tube guides it straight to the adjuster, no fiddling around trying to find the thing. All that shows is a hole about 2.5 mm in the cowl.