Steamer

Just pull the engine, rebuild it.

If the shaft and counterweight are still intact, how about cutting a strip of muffler & exhaust leak tape/cloth and wrap the shaft tight, and wedged in there. Maybe some tie wire over that as well.

I think you're misreading the FSM. Or it is poorly translated into the Engrish. The battery is applied to the signal wires into the igniter. It simulates the small voltage pulse made by the dissy. When the 1.5V battery is momentarily scratched...