7. CYLINDER HEAD/VALVES (Mongoose/KXR 90) Mongoose/KXR 90/50 Measure compressed force (valve spring) and installed length. Replace if out of specification. Service limits: IN : 3.474.27kg(at 26.0mm) EX : 8.2910.19kg(at 29.0mm) Check the intake manifold and O-rings for wear or damage. O-ring 7-11