It could be alot of things. Don't ride her until you find out what it is. Damage could be getting done. First is relatively cheap: Buy a primary gasket, and open her up. It might be something as simple as your primary chain tensioner could be mal-adjusted, or the foot could be damaged. It could be a loose copmpensator bolt. It could be something wrong with your stator. The list is endless. You'll just have to open her up and start looking.
Noise can fool you. It could come from the cam chains/tensioners and sound like it is coming from the primary side.
Start with the most apparent, and least expensive. Then work from there.
Good luck,
Rich P