Hello everyone: I have always been a CRF 450 owner, and not yet have had any valve issue, anyway I take care of them every 25-30 hours. But I heard YZF's 450 were much more reliable and didn't need that much manteinance, oil as well... and were much more reliable in general...... I also have to say I heard the complete opposite story, plus much more expensive and difficult to find components for YZF's and five valves instead of four!! I am planning to swsitch but not sure, please give me your views!! thanks a lot !!