worthyking

Hey guys, I have an 03 YZ450F that I just recently bought. After riding a couple weekends I noticed a loud engine noise. To me it sounds like valves knocking. Reading the forums I have found other threads that say it's normal for these bikes, but I just want to be sure before I do anything rash. So...I took a video clip of the bike idling and wanted to see if you guys could take a listen and tell me if i need to worry. Here it is: