If I had to take a guess, I would guess that it is the tip over switch. It would be difficult under those conditions to notice the fuel shutting off. Residual pressure would keep the engine supplied with fuel for a couple of cycles. If the light is just flashing on, it may not cut the fuel to the engine enough to notice. You may want to look up the wiring for your bike, to see how to by pass the switch. If it is anything like my 85, (and the wiring of the switch most likely is the same), you simply need to short one wire to ground. This will allow the FI relay AND the fuel pump relay to complete their circuits when energized by the ECU. Once you by pass the switch, if the problem goes away, you have found the problem. I had to bypass mine because it would kill the engine randomly.