If it comes on whilst riding, the two stroke oil is low. There's quite a reserve though, so don't panic and pull up immediately.
It comes on initially to show you the light bulb works, and goes out once the engine is running.
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball