2009 Arctic Cat 366 ATV Service Manual, Page 38Get this manual
3Acceptable diameter range (exhaust valve) must be within specificationsMeasuring Valve FaceSeat Width 1Using micrometer, measure the width of the valve face CC134D
ATV-1004
2Acceptable width must be at or above specificationsMeasuring Valve Face Radial Runout
NOTE: The valve seals must be replaced