Can't help you with the tumbler issue at this point! But you can get the electrical portion of the ignition switch seperated. There are three screws under the electrical connector, with one of the flat 1" diameter abrasive wheels in the Dremel tool you can just below the parting line of the electrical switch section, use it to cut the three screw shafts. With these screws cut the switch section will seperate from the locking section, you can then use a screwdriver to turn the ignition switch, with the switch turned to the first indent you can pull the connector off the rear of the switch. With the connector of you can remove the cut off screw heads, and then put the connector back on the switch and use a screwdriver to turn the switch to start and stop the engine while you figure out what to do about a locking mechanism