Checking Spark Plugs (Conventional Ignition System)

PROCEDURE

Normal engine operation depends largely on the condition of the spark plugs. Remove the spark plugs and inspect them. If the insulator is light brown or grey-steel in colour, the carburettor is adjusted correctly and the plug is working properly. A light grey or white insulator indicates a lean mixture. Black deposits on the plug indicate a rich mixture. If the electrodes and insulator are oily, the spark is either intermittent or the piston rings are worn. Before installing a spark plug, clean it with a wire brush, wash it in petrol and dry it. Adjust the spark plug electrode gap by bending the side electrode. Do not bend the centre electrode, as this can damage the spark plug. Tighten the spark plugs to a torque of 20 N·m.