Just picked up a 1997 XR600R. My background/experience is with the CRF250X. On those little bikes, the right intake valve is usually the valve that zeros first.

I checked the valve clearances this morning on the 600, all were in spec except the left exhaust. My question is, which valve on these bikes usually goes out of spec first? Or is there one?

Thanks in advance.

Unlike your experience with the 250, the valves on the 600 last for a very long tine. Usually the valve seat and valve face wear past spec, but the clearance doesn't change much. If fact the bike will still run pretty well. In fact the only time I have ever seen the clearances decrease fast is when I had a valve seat fail.