7. CYLINDER HEAD/VALVES (Mongoose/KXR 90) Mongoose/KXR 90/50 VALVE/VALVE GUIDE INSPECTION Inspect each valve for bending, burning, scratches or abnormal stem wear. If any defects are found, replace the valve with a new one. Check valve movement in the guide. Measure each valve stem O.D. Measure each valve guide I.D. Subtract each valve stem O.D. from the corresponding guide I.D. to obtain the stem- to-guide clearance. Service limits: IN : 0.06mm replace if over EX: 0.08mm replace if over If the stem-to-guide clearance exceeds the service limits, replace the cylinder head as necessary. CYLINDER HEAD INPECTION Check the spark plug hole and valve areas for cracks. Check the cylinder head for warpage with a straight edge and feeler gauge. Service Limit: 0.05mm repair or replace if over VALVE SPRING INSPECTION Measure the free length of the inner and outer valve springs. Service Limit: Inner: 30.8mm replace if below Outer: 33.5mm replace if below 7-10