How to Change Lawn Mower Spark Plugs

Image via jhritz on flickr.

For safety precautions, it is always best to turn off all power to the machine before repairing or replacing parts. It is also a great safety precaution to wear gloves and safety glasses while operating on a machine. It is always best to refer to the machine’s user manual if it is available. If the machine did not come with a user manual, contact the manufacturer or distributor to request a copy.

One of the most important parts of a lawn mower is the spark plug. The spark plug is what completes a circuit from the battery to the engine in order to power the machine. Taking a lawn mower to a repair shop for routine maintenance can be costly, and with a little education, most maintenance can be done at home for a fraction of the cost. Another benefit of replacing parts and doing routine maintenance at home is the fact that there are no shop hours that must be adhered to.

The first thing one has to do in order to change the spark plug is to find the spark plug. Different types (push or riding mower or riding tractor) may have different locations for the spark plugs. Once you have located the spark plug, remove the boot (the rubber cover that protects the spark plug head) and use a socket wrench or crescent wrench to gently twist the spark plug loose. Once the spark plug is loose, gently remove it from the spark plug wire or socket.

Use the old spark plug to double check the new spark plug. Make sure the gap is spaced correctly (most times they are pre-aligned, but it never hurts to be cautious) and that the correct spark plug has been purchased. Using the wrong spark plug or using a spark plug with the wrong gap measurement may cause extensive damage to the lawn mower.

Once satisfied that you have the correct spark plug, place the new plug into the spark plug wire or socket. Tighten by hand only. Using a wrench to tighten the spark plug may apply too much torque. Using too much torque on a spark plug may strip it or cause other damage. Once the spark plug has been replaced, put the boot or cover back on the head of the spark plug.

The spark plug ignites small explosions in the engine, which gives it more power. Since the spark plug is actually inside a part of the engine, it is subjected to high heat and corrosion as well as the basic wear and tear. Since the spark plug is actually a power producer, a faulty spark plug may not produce enough of a spark to cause the fuel to combust, or it may not spark at all.

Even if the lawn mower is starting and running correctly, replacing the spark plug is a maintenance routine that should be performed at least once a year to maintain optimal performance from your lawn mower.

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