Problem
Valve sticking.
Cause
Deposits on valve stem. Worn valve guide. Warped valve stem. Insufficient oil. Overheating valves.
Solution
Clean or remove valve stem deposits. Replace valve. Check oil or service lubricating system.
Problem
Valve burning.
Cause
Valve sticking. Distorted valve seat. Valve tappet clearance too small. Spring cocked or weak. Overheated engine. Lean air fuel mixture. Preignition. Detonation. Valve seat leakage
Solution
Check cooling system, tighten cylinder head bolts. Adjust. Replace spring. Check cooling system. Service fuel system. Clean carbon from engine, use cooler plugs. Adjust ignition timing, use higher octane fuel. Replace valve face and seat. Replace valve guide.
Problem
Valve breakage.
Cause
Valve burning. Detonation. Excessive valve tappet clearance. Valve sticking. Scratches on valve system.
Solution
Adjust ignition timing, use higher octane fuel. Adjust. Replace valve.
Problem
Valve-face wear
Cause
Excessive valve tappet clearance. Dirt on face.
Solution
Adjust. Clean, check air cleaner.
Problem
Valve deposits
Cause
Carbon from rich mixture. Worn valve guides. Carbon from poor combustion. Dirty or wrong oil.
Solution
Service fuel system. Replace. Service fuel system, ignition or service engine. Replace oil.
