Things You'll Need
Spark plug gapper
Spark plug socket
Lawn Boy lawnmowers contain small, simple engines that employ single spark plugs to ignite the air/fuel mixture to keep the mower running. Depending on usage and environment, it's not a bad idea to replace the plug every year or two. As the spark plug is used, the center electrode wears down, making it less and less effective as time passes. The spark plug can also foul over time, also decreasing its effectiveness. Anyone with decent mechanical aptitude can change the spark plug in a Lawn Boy in a matter of minutes.
Gap the spark plug using the spark plug gapper, which you can purchase at any auto parts or lawn machinery store. The gap is determined by the year, make and model of Lawn Boy engine you own, so reference the Lawn Boy's specific owner's manual for gap specifications. You can also consult an authorized Lawn Boy dealer for this information.
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Pull the spark plug wire off the plug by hand. You will want to grab the boot and pull it, not the body of the wire. Pulling the body of the plug wire can cause damage to the wire.
Put the spark plug socket onto the socket wrench and use the combination to remove the old spark plug by turning it counter clockwise.
Thread the new spark plug in by hand and then tighten it down with the socket wrench and spark plug socket.
Plug the spark plug wire onto the new spark plug by hand.