Testing the starter motor solenoid. 

Once again, if you are uneasy with electrics, pass on this bit. 

   Find the solenoid, this can sometimes be a little difficult, as it may be mounted on top of the starter motor ( as on B.M.W. boxer engines ).
    Having located the beastie, you will notice two of the wires are much thicker than the others.  These are the wires that feed the starter motor, and should be left well alone.
    Find the wire that goes from the solenoid to the start button, and bridge it with the wire that operates the relay in the solenoid.  If there is no "Click" as the solenod energises, then it is shot.  If the solenoid works, and the starter motor spins, then you have a fault with either the ignition switch, the start button or one of the electrical interlock switches.   Good luck in finding which one.  Just "bridge" them, one at a time until the thing works.  I hope you have good eyesight and an up to date wiring diagram.