22-10-2021, 08:09 PM
Jon, on some later dynamo, particularly well used neglected units, the bearing housing can be worn allowing fore and aft movement of the armature shaft. You need to correct this by machining/shimming dependant upon the specific issue you may or may not find on yours, if not dealt with this movement plays havoc with ignition timing and is not good for the timing gears.
Black Art Enthusiast