So my son got a new bike and when he got it home he started it and ran fine except when he revs it, it makes a noise when the rpms fall back down. I was thinking the timing chain or guides were bad, so we opened it up to put the new chain and guides in. When I dropped the oil there were a few copper flakes on the drain plug. At this point we removed the cams and the exhaust cam bearing seems to have some slop in it, so he ordered new cams for it. I'm just wondering if the cam bearing would make a noise like that or if I'm on the wrong path here. Any opinions would be appreciated.