2001 Polaris Sportsman 400-500 DUSE and H.O. Service Manual, Page 98Get this manual
VALVE INSPECTION
1Remove all carbon from valve with soft wire wheel2Check valve face for runout, pitting, and burnt spotsTo check for bent valve stems, mount valve in drill or use "V" blocks and dial indicator
3Check end of valve stem for flaring, pitting, wear or damage (A)4Inspect split keeper groove for wear or flaring of the keeper seat area (B)NOTE: The valves cannot be re-faced or end groundThey must be replaced if worn, bent, or damaged