What causes spark plugs to go bad?

The main causes of spark plug damage include carbon deposit accumulation, electrode erosion, insulator cracking, and air-fuel mixture imbalance. Carbon deposits, typically caused by incomplete fuel combustion, engine overheating, or improper ignition timing, adhere to the electrodes, hindering spark generation and potentially completely blocking the spark plug in severe cases. An overly rich air-fuel mixture (due to factors like excessive carburetor fuel level or clogged air filter) causes carbonization of unburned gases at the electrodes, while substandard spark plugs or incorrect specifications (such as improper heat range) can accelerate deterioration. Furthermore, engine oil consumption, ignition system malfunctions (e.g., magneto demagnetization), or improper electrode gap settings (too wide or narrow) may also contribute to failures. Regular inspection of spark plugs is advised, with replacement every 20,000 to 30,000 kilometres, using premium-quality components that meet OEM specifications. Maintaining proper fuel quality and engine upkeep is essential to prolong spark plug service life and ensure consistent engine performance.