How to Adjust Magnetic Coils on a Lawn Mower

Ensure your lawn mower is turned off. Take the plastic engine cover off. This reveals the plug wires and spark plugs. Disconnect the plug wires that connect to the spark plugs.

Find the magnetic coil. The plug wires you just disconnected lead back to the coil, so follow their trail to locate it. There is a separate, thin wire that connects to the plug beside this coil and acts as a ground. Pull this wire out of the plug.

Connect one of the plug wires into an old spark plug. Use insulated pliers to press and hold the spark plug against the lawn mower's engine block.

Attempt to start the lawn mower. Look carefully for any blue sparks near the attached plug. If the spark is not blue and is instead yellow or orange instead, the magnetic coil will need to be replaced by your manufacturer.

Look for the air gap of your lawn mower if there is simply no spark at all when attempting to start your mower. The air gap will be found directly between your magnetic coil and the magnets on the flywheel at the back of the engine case. Ensure this gap is very narrow. Depending on the manufacturer of your lawn mower, this air gap should be between 0.010 and 0.015 of an inch. If the width is larger than a playing card you will need to loosen the magnet coil with a wrench and make the gap adjustment.

Turn on the lawn mower again and check for blue sparks once more. You should now produce sparks upon igniting your engine. The magnetic coil is properly adjusted.