Swapping magnetos isn't such a bad idea! I'll try that as a last resort.
I hooked the wires up to the ol' multimeter, and this is what I found:
Black wire: engine kill (ground it and engine dies).
Yellow wire: 12V
Green and Red wire: 6V
What in the world am I supposed to do with 12 volts? When I bought the engine, the 6V and 12V wires were connected together. Should I leave them that way?