The color of insulator appears powder white,yellow,yellowish brown,green and black.
Cause: When an engine operates in low load speed,heavy looad condition,the temperature of spark plug increases further,then because of the increase in temperature,the conductivity of the lead compound formed on the insulator surface increases,therefore causing the misfiring of the spark plug.
Action: Avoid using lead gasoline,or change to use a hotter type of spark plugs.
