I believe that the unit you are looking at is for a tachometer. I would venture a guess and say it is for an Airguide dash tach. Since motors of this vintage didn’t have alternators on them, the only way you could install a tach was to have a direct reading off of the ignition system. This unit is installed inline with one spark plug lead. The gray wire goes up to the tach, the black ones connect to the spark plug wire and spark plug.
This reply was modified 5 years, 2 months ago by RICK EICHRODT.