While doing a tuneup on a recently purchased 01 YZ426 I checked the valve clearances and they were fine. When I moved onto the cam timing check however, I ran into a little problem. The intake cam was off 2 teeth and the exaust was off 1. I have corrected the problem but am trying to determine what caused it. Previous owner/mechanic error or is there an underlying issue with the engine. The tensionor operates well.