Got this bike from my friend not too long ago, and it was having some problems starting so I decided to check valve clearance. Sure enough they were getting tight. When I was taking the cams out, I set them aside and went on with the job. When I went to put them back in, I noticed that the exhaust cam was missing the little metal ring half that sits under the cam. There is clearly a groove where there should be one, and I don't know if it somehow fell down into the engine or if it was missing when I bought the bike. I fear that it fell down into the engine... I haven't gone any deeper into the bike than a valve adjustment, so if you guys have any video links or walkthroughs you think would help guide me they'd be much appreciated. I found a European version of the owners manual so maybe it will have everything I need. Thanks!