During a run out today, had to pull over and stop when another rider had a small snag. anyway, he got going again so I went to start my bike. It turned over slowly, fired up, showed about 10.8 volts then cut out, wouldn't tick over. Started her again and kept the revs on with the throttle till we were under way. Volts around 11.0, then fuel warning light came on and gauge stopped working. After a few minutes the light went out, the gauge came up and voltmeter back to 12.5 volts (I know it should be higher but I need to get round to connecting the meter direct to the battery, not a live on the clock cluster, just haven't done it yet). She was then fine for the rest of the day.
I don't know what was going on, but I'm off to fine a bucket of sand to bury my head in..... :roll:
Sorry I don't have a definitive answer, but I would check connections in the charging system. I have recently had the stator/rectifier connection overheat and fry which caused some strange things, not system failure, but fuel gauge light coming on and going off and dips in voltage. After I fixed the connection, things seem to be good. (for now at least)