Presumably it must have a starter solenoid somewhere which is operated by the key switch, trace the thick wire from the motor and see where it goes, if it goes to a small box and another thick wire goes to the battery then that box is the starter solenoid if the wire goes straight back to the battery then the solenoid is in the motor. There should be 1 or 2 thinner wires, depending how it's wired, one of which will come from the start switch, if there is only one wire then the switch will supply 12V when turned, if there are 2 wires then the switch will ground the wire when turned. You should be able to sort it out with a cheap meter from Maplins or somewhere similar. I'm assuming here that these things are still reasonably simple, if they have gone the same way as cars and the whole thing is driven by a computer then take out a new mortgage before you take it to the dealers. :-)