Burning gear oil

[jlohe1973]

I have a 2015 roketa mc 46-150. I was riding it yesterday and there was a whining noise coming from the gear box. Turned around to go home and before I got home I smelled gear oil and noticed gear box was leaking gear oil and it was smoking. I replaced gear oil about 300 miles ago. Bike does start and run but bad noises coming from gear box and has no power and barely rideable. Any ideas plz help it's my only means of transportation