2009 Suzuki 400 LTZ Quad Sport Service Manual, Page 176Get this manual
Engine Mechanical: Valve face wear Visually inspect each valve face for wearReplace any valve with an abnormally worn faceThe thickness of the valve face decreases as the face wearsMeasure the valve head "a"If it is out of specification replace the valve with new oneSpecial tool0990020101 (Vernier calipers (115 mm, 150 mm)) Valve head thickness "a" (IN& EX Service limit: 0.5 mm (0.02 in)
Valve stem wear Measure the valve stem O.Dusing the micrometerIf it is out of specification, replace the valve with new oneIf the valve stem O.Dis within specification but the valve stem deflection is not, replace the valve guideAfter replacing the valve or valve guide, recheck the deflectionSpecial tool (A): 0990020205 (Micrometer (0 25 mm)) Valve stem O.DStandard (IN: 4.975 4.990 mm (0.1959 0.1965 in) Standard (EX: 4.955 4.970 mm (0.1951 0.1957 in) NOTE If valve guides have to be removed for replacement after inspecting related parts, carry out the steps shown in valve guide replacementRefer to "Valve Guide Replacement (Page 1D-36)"