The bike has been perfect. Have studied the 2006 YZ450 reliability data from many experiences on this site. Has about 50 track hours by a plus 40 Int. rider. Ridden fairly hard... for me, I guess. Quality JASO oil changed regularly, clean air filter etc. I am going to replace the clutch plates, top end and timing chain, using OEM pieces. My mechanic insisted on having the head rebuilt on my 2005 using stainless springs etc. I am guessing that is overkill and am not planning head work, except for valve adjustment as needed. Does this sound about right? Thanks.