The 440 will crank, but not start by twisting the key in the ignition.
However, if I take a screwdriver and short circuit the starter solenoid the engine will fire up pretty much immediately.
I've swapped the starter solenoid without getting any different result.
The ignition is controlled by a MSD 6AL box.
I'm going slightly mad here. Any suggestions?
Edit: Forgot to mention that the neutral safety switch has been tested OK.