How to Change a Lawn Mower Spark Plug

Most garden lawn mowers are going to have a simple single-cylinder engine. With the exception of big commercial mowers or larger garden tractors, which may be a V-twin. That means they are fairly easy to service, including changing the spark plug.

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How do you change a lawn mower spark plug? Let’s start from the beginning! Most garden lawn mowers are going to have a simple single-cylinder engine. With the exception of big commercial mowers or larger garden tractors, which may be a V-twin engine. Either way, they are fairly easy to service, including changing the spark plug.

Older lawn mowers had a magneto style which supplied current for the ignition, but newer designs often use electronic ignition for spark delivery.

Now that we have a bit of lawnmower history, the question still is, how do you change a lawn mower spark plug? No matter what type of mower you have, the method of changing the spark plug on the engine will be the same.

Instructions

  1. With the mower on level ground, remove the engine cover and/or heat shield.
  2. Disconnect the spark plug wire from the plug and insulator.
  3. Place the spark plug socket over the plug and ratchet it out by turning counterclockwise until the plug is removed.
  4. Installation is just the reverse of removal. Screw in the new spark plug. Make sure it is torqued down snugly enough to not loosen up again. Reconnect the plug wire, and reinstall the engine cover.

 



TIP

Most new spark plugs for mowers will come pre-set with the appropriate electrode gap. But it is still a good idea to verify the gap with the proper feeler gauge so that you can be sure that the plug is gapped properly and ensure the best firing of your engine.

 


 

 

NOTE: Replacing the spark plug is recommended annually. During the season it is still worthwhile to pull the plug out and inspect it. If it does not appear to be burned, eroded, or fouled, set the gap once more, cleaning it with a wire brush and some solvent (aerosol brake cleaner will work fine) and reinstall it.

Don't forget a spark plug wrench