When the fault occurred the other night - I pushed the starter button and the starter motor whirred it's heart out with no fuel pump whine and not a sputter from the engine.
Then - standing beside the bike - I unplugged the tank without jostling or even touching the tank itself and pushed the starter again. This time the bike sputtered .
Clearly I had no spark before I unplugged the tank - and clearly I did have spark after I unplugged the tank.
James - I absolutely agree it doesn't make sense - but it was clearly observed. Furthermore - I had a similar thng happen last week during troubleshooting - although I didn't recognize what was happening at the time.
Here's the theory - the hot G/W wire going in to the fuel tank is shorting to ground inside the white molded plastic base of the fuel level sender. That G/W comes from the fuse panel which is fed from a G/R wire from the fuel injection relay. The ignition control unit also connects to the fuel injection relay - through the Y/Br wire and it's possible that the short is travelling to the spark box through that wire.
I have the FI relay on my desk in front of me - -it looks good physically and the contacts don't look burned. Unfortunately - a new one is 3-4 weeks away through my local supplier and it's not cross reference-able to anything off-the-shelf.
I spent the morning trying to agree that it's a kill switch problem and that the lights on the dash could somehow stay on even though this switch was failing - but I just couldn't get there. Furthermore - the starter button works just like normal and if there's one thing that won't work without a good kill switch - it's the starter button.