170cc scooter problem

[envdevo9]

I have a bbk on my 150cc. Right now im having problem with my electrical system. I have a fully charged battery on the scooter, i hooked up a multimeter to it and it reads 12.50ish with the engine running. But it starts jumping to 7.30ish and then back to 12.50ish. Im not on the throttle at all. Not sure if maybe something to do with my stator or regulator?

Thanks