I have a 2004 CRF250R and I want to replace the valves and springs. I am considering the Kibblewhite kit. Will these eat up the stock 2004 seats? Do I need to get hardened seats?
The seats in the CRF250R are very compatible with the Kibblewhite stainless steel valves. Given how hard the stock seats are, the stainless valves are actually a better match than titanium is.
Just make sure you get a good valve job done before you install any new valve. Valve longevity is very much a function of how well the seat and valve seal together, and only a proper valve job will get you that correct seal.
When you have the head apart make sure and closely inspect the valve seats for chipping and cracking. Some of the early 2004 250Fs had seats that were too hard, to the point of being brittle, which caused some chipping of the seats.
The pics below were from an early serial number CRF250 that I worked on. The valves and springs were really shot which was a major contributor to the seats cracking.