Check fluids & change if you haven't already to bike-specific full synthetic. While you're at it, look at your drain plug. Small metal shavings are normal, look for anything abnormal. Adjust Primary chain for kicks, if too loose it can knock around in there. Hopefully, it's as simple as one of those if nothing is just loose...
Edit: One thing to consider is you hadn't noticed it till now. It's a Buell, but it has a Harley heart and all the noise that entails.