Sounds like valve train noise but I'd want to make sure the thing was at OT before I worried too much about that. When it heats up and the tolerances shrink the noise should diminish some. I've got close to 2000 miles on mine and I had some noises that made me nervous too but either I'm used to them now or they've worked themselves out over time. Get a nice long screwdriver and hold it up to the valve cover and put your ear against the handle. If it's coming from that area, you'll be able to hear it clearly.