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Problem and possible cause Remedy
1. Oil leakage
1) Loose oil drain plug Tighten
2) Faulty oil drain gasket Replace
3) Loose main bearing cover bolts Tighten
4) Faulty main bearing cover gasket Replace
5) Crankshaft oil seal (front, rear) defect
Replace
2. Oil up
1) Faulty piston oil ring Replace
2) Piston ring seizure, wear or poor contact Replace
3) Excessive wear of piston and/or cylinder Replace
4) Faulty stem seal Replace
5) Excessive oil level Adjust oil level
6) Breather defect Repair or replace
1. Fuel system
1) Clogged air cleaner Clean or replace
2) Faulty needle valve and/or high fuel level in
float chamber
Repair or replace
3) Choke does not open fully Repair or replace
2. Engine core components
1) Low compression Check and repair
2) Overcooling
Check and adjust load
and/or engine speed
1. Ignition system problems
1) Loose ignition system wiring Inspect and tighten
2) Improper or faulty spark plug Clean or replace
2. Fuel system problems
1) Lean or rich fuel/air mixture
Clean, adjust or replace
carburetor
2) Carburetor contamination Overhaul or clean
3) Dirty or clogged fuel lines Clean or replace
4) Air mixing from air intake system joints Tighten; replace gasket
3. Cylinder head
1) Carbon deposit in combustion chamber Clean
2) Leakage from cylinder head gasket Replace
4. Valve system problems
1) Improper valve clearance Adjust
2) Valve heat deterioration Replace
3) Worn or broken valve spring Replace
4)Improper valve timing Adjust
Excessive engine oil consumptionHigh fuel consumptionAbnormal engine noise