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I am the third owner of my '06 250X and I wanted to know how to tell if I have stainless steel valves because I will be checking the clearances soon. The reason I ask is because the second owner told me that the first owner did a few modifications to the bike and that he said the valves were good for years yet. When the second owner bought it he had a shop check them, and they said the same thing. It also has a noticeable lack of top end power compared to my brother's WR250F and I know SS valves are heavier and have stronger springs which could cause this. Any ideas on how to tell without pulling the head off.

I am the third owner of my '06 250X and I wanted to know how to tell if I have stainless steel valves because I will be checking the clearances soon. The reason I ask is because the second owner told me that the first owner did a few modifications to the bike and that he said the valves were good for years yet. When the second owner bought it he had a shop check them, and they said the same thing. It also has a noticeable lack of top end power compared to my brother's WR250F and I know SS valves are heavier and have stronger springs which could cause this. Any ideas on how to tell without pulling the head off.

First, stainless steel intake valves are not going to be the cause of lack of power. It's not accurate that the added weight of stainless intake valves would consume a significant amount of engine output.

Second, if the valves are in spec and not moving then run them until they move and then plan a valve job and vale replacement.

Third, if the valves are cheap stainless steel valves they could be a two part construction (like the Honda OEM exhaust valves). If this is the case a magnet on the back half of the stem will tell you. If not the only real way is to remove the valve and weigh the valve.

Ken