2004-2009 Suzuki LT-Z250 Service Manual, Page 66Get this manual
VALVE STEM WEAR Measure the valve stem outside diameter with the micrometerIf the outside diameter is not within the specified value, replace the valve with new oneIf the valve stem outside diameter is within specification, but the valve stem deflection is not, replace the valve guide with new oneAfter replacing the valve or valve guide, check the deflection and Valve stem O.DStandard (IN)5.475 5.4 90 mm (0.2156 0.2 161 in) (EX)5.455 5.4 70 mm (0.2148 0.2 154 in)09900-20205: Micrometer (0 25 mm)