TM 10-3930-653-14&P Condition Probable cause Corrective action Seized valve seat Improper valve clearance Adjust Weakened valve spring Replace. Thin valve head edge Replace valve Narrow valve seat Reface. Overheating Repair or replace. Over speeding Drive within proper speed Sticking valve guide Repair. Excessively worn Shortage of engine oil. Add or replace oil. cylinder and piston Dirty engine oil Clean crankcase, replace oil and oil filter element. Poor quality of oil Use right oil. Overheating Repair or replace. Faulty assembly of piston with connecting Repair or replace rod Improper piston ring clearance Adjust. Broken piston ring Replace Dirty air cleaner Clean. Too rich mixture Adjust Engine over run Drive at proper speeds Sticking choke valve Clean and adjust Overchoking Statt correctly. Malfunctioning Shortage of engine oil. Add oil. connecting rod Low oil pressure Correct. Poor quality of engine oil. Use right oil. Rough surface of crankshaft. Grind and replace bearing. Clogged oil passage. Clean. Bearing wear or eccentricity. Replace. Improper bearing assembly. Correct. Loose bearing. Replace. Connecting rod alignment incorrect Repair or replace. Malfunctioning Shortage of engine oil Add or replace. crankshaft bearing Low oil pressure. Correct. Poor quality of engine oil. Use right oil. Crankshaft journal worn or out-of-round. Repair. Clogged oil passage in crankshaft Clean. Bearing wear or eccentricity Replace. Improper bearing assembly Correct. Eccentric crankshaft or beanng Replace. 4 - 22