Denny, that type of needle bounce is almost always caused by a rough spot in the cable housing that sets up a twist in the cable at a specific speed. I've chased that type of problem repeatedly, and I've found about the only surefire fix is replacing both the inner cable and the housing as a matched pair. Most shops that do big truck tachometer repairs can custom fabricate a speedo cable using whatever threaded ends are appropriate for the old stovebolts. Use your old cable and housing as a pattern.
Jerry
Edit: For calibrating the zero point, I usually install the needle just below the stop pin, and gently lift it over so the return spring holds it lightly against the pin. I suppose the needle could be twisted on the shaft, carefully, if necessary. Just hold the shaft with one plier, and turn the needle with your fingers, or another plier. Those plastic needles can get VERY brittle with age, however, so be very gentle.
Jerry
Last edited by Hotrod Lincoln; 11/04/2007 4:14 PM.
