On my 2000 Dutch Star, the Stewart Warner electric speedometer has gone goofy. It reads all over the place while driving. It will go from 85 to 0 to 35 and more while riding at about 60. I'm currently...
GMC products had the same symptoms for a few years. Turned out it was the stepper motors that drove the needles. You could by one on line and solder it in place of the old one. You had to remove the gauge cluster though.