You don't have a stock regulator but can add one if you want. If I recall correctly, you just splice it into the blue wire coming out of the stator (lighting wire) and I drilled a hole in the frame and I think it just grounds to the frame. Or you can go with an aftermarket regulator that probably has a separate ground wire.
On your model, the battery acts as the only regulator but if it ever goes completely dead, it won't serve that function. That's why Yamaha probably decided to add a separate regulator on later models (redundancy to save headlights and other lights from blowing).