I'm in the market for a 450 dirt bike. I'm really liking the WR450, but these are hard to find and am seriously looking at the CRF and YZ. I've been looking at these forums and I'm getting the impression the CRF's have a lot more valve issues than the Yamaha's. Is this true? or am I'm looking at this wrong. And yes I know the WR is a trail bike which is what I want (mostly trail riding) but finding a CRFX is nearly impossible and I'm willing to sprocket a CRF or YZ to make them work.