Well im back in the hunt for a new dirt steed and the yz450f 06+ is still at the top of my list as far as what i want. Last time that happened was summer 08 and i did tons of research, but i ended up getting a nice yz250. Anyway, I remember most of the questions I asked then and their answers. One thing I don't quite remember is the question that i just possed in the subject. I remember someone telling me (i think it was Grey but not sure) that once the valves have required adjusting, the likelyhood that they will continue to go down hill from there is high. eventually leading to the need for a new valve train and head. Or maybe it's only the case if the valve seats have worn not the valves?? I don't remember.... Either way, should i avoid 06+ Yz450fs that have had their valves adjusted already???