I'm talking about the clink clink noise at idle. I have a well worn 06 yz450f. My brother has a brand new 07 yz450f. The noise is there on both bikes. However in my 06, it is louder. Has anyone determined what the noise is? What would it mean when it gets a little louder? I've checked the 06 valves... good. Always starts right up. Runs great. The 06 noise doesn't get louder when you rev it but actually appears to go away at anything other than idle. The bikes sound the same off idle. This is driving me nuts. What's the noise?