TM 10-3930-653-14&P Condition Probable cause Corrective action VALVE  ADJUSTMENT An Improper adjustment of valve clearance Adjust Noise of timing chain Adjust the tension or chain An excessive end-play on crankshaft Disassemble engine and renew main bearing ABNORMAL COMBUSTION (back fire, after fire run-on etc ) Improper ignition timing Improper Ignition timing Adjust ignition timing Improper heat range of spark plugs Use specified spark plugs Fuel system trouble Damaged  carburetor  or manifold gasket Replace them with new parts (back fire, after fire) Faulty carburetor jet Disassemble carburetor and check it Improper function of the float Adjust the level, and check needle valve Uneven idling (Run on) Adjust Defective cylinder head, Improperly adjusted valve clearance Adjust etc. Excess carbon in combustion chamber Remove head and get rid of carbon Damaged valve spring (back fire, after fire) Replace it with a new one EXCESSIVE OIL CONSUMPTION Oil leakage Loose oil drain plug Tighten it Loose or damaged oil pan gasket Renew gasket or tighten It Loose or damaged chain cover gasket Renew gasket or tighten it Damaged  oil seal in front and rear of Renew oil seal crankshaft Loose or damaged rocker cover gasket Renew gasket or tighten it Improper tightening of oil filter Renew gasket and tighten it with the proper torque Loose or damaged oil pressure switch Renew oil pressure switch or tighten It Excessive oil Cylinder and piston wear Overhaul cylinder and renew piston consumption Improper location of piston ring Remount piston rings gap or reverse assembly of piston ring . Renew rings Damage  piston rings Repair or renew piston and cylinder 4-6