[ossiblue]

There's a little trick available on a 912. Look in the engine compartment at the left rear corner where the electrical connections are. You should see a yellow wire that is not connected to anything. If you touch the end of that wire to a hot lead, the starter will crank. If it doesn't, then the problem is likely with the starter/solenoid. If it does crank, the problem is with the switch or high resistance in the start circuit.

Note: It's been many years since I owned a 912, but the above is from what I remember. I owned two 912s and both had the wire as did all of the ones I saw from other owners.