Robin EY40 - Engine Knocking Diagnosis; Carburetor Backfire Troubleshooting

ENGINE KNOCKS
Low-quality gasoline.
Engine operating under heavy load at low speed.
Carbon
or lead deposits in the cylinder head.
Spark timing incorrect.
Loose connecting rod bearing due to wear.
Loose piston
pin due to wear.
Causes
of engine overheat.
ENGINE BACKFIRES through CARBURETOR
1) Water or dirt in gasoline, or low-grade gasoline.
2) Intake valve stuck.
3) Valves overheated, or red-hot carbon particles in the combustion chamber.
4) Engine cold.
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