sharp valves

[russell wrx]

im in the process of rebuilding the top end on my zxr750 at the moment and i have just started grinding the valves in. I noticed that 2 of the inlet valves are quite sharp where they sit in the seat and seam to sit further down in the head. Do they need replacing?

[DGXR]

Yes they need replacing. That kind of wear is called "dishing" and happens when the valve face starts wearing at the seat contact and is slowly receding into the head. So they need to be replaced, along with a new valve seat cut. I have the head apart on one of my bikes too and I say just replace everything that is even slightly worn so it's done right and you don't have to tear it apart again for a loooong time.

[russell wrx]

ok cheers ?