Tony, look here. It may be good to know what caused the light to come on
The FI is the Fault Indicator light
The next time it comes on, pull the bike over and leave it running. Put it in neutral and then put the side stand down.
This will cause it to emit the code to the FI light again. Count the long/short pulses - they will indicate the fault code. Long pulses = 10, short pulses = 1, so long, long, short, short, short = 23.
You can Google GL1800 fault codes and find out what each one means.
Good luck!