dyna III ignition/Reverse

Remember me? I'm the ass**** that stuck a starter on the sidecar wheel and blew up his Dyna II ignition controller. well I finaly figered out what happened. To back up I pulsed the starter, each on time draged the battery down to almost o volts then I released it, allowing the battery to recover. When it was on a tremous mag. feild built up, then when I released it, the colapsing feild on the starter winding made a huge reverse voltage spike. Evan though the solenoid contact were open, there must have been a spike big enough to jump them and blow up the controller.