It does sound like their is something funny there as where the cable connects to (should be a L sharped picece) that connects to an arm which should make the butterfly move. When when the engine is running the wind vein helps control that by the air coming from the flywheel.
This whole experience with this mower has been funny but on the positive side I have learnt a lot. If I hadn't invested so many hours in this I would have given up long ago. Would it help if I took some close-up photos of the governor mechanism?
