siren
The siren you are hearing is probably the overheat sensor. If the siren is on when the engine is cold then you probably have a faulty sensor. The sensor is located on top of the engine between the spark plugs.
Cold engine......siren on......unplug sensor......siren quits.....faulty sensor.
If the siren only comes on after you have ridden a bit then the engine is probably overheating and you'll need to look for restrictions in the cooling system. Good luck,
DAWG