How to Replace a Walk-Behind Lawn Mower Spark Plug

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Before you being the process of changing your mower spark plug, make sure you have the right replacement part.  For all your maintenance, it's best to use genuine factory lawn mower parts.  They are built for your machine and will help maximize its performance and lifespan.  The correct mower spark plug for your machine is listed in your engine operator's manual.


Make sure you also have the tools you need to replace a lawn mower spark plug, including a spark plug socket wrench and a gap tool.  Keep in mind that the instructions for changing the spark plug on your MTD lawn mower model may be slightly different.

Step 1: Disconnect the mower spark plug wire

Begin by disconnecting the mower spark plug wire.  The engine should be cool when you replace your lawn mower spark plug..

Step 2: Remove the old mower spark plug

Use a spark plug socket wrench to remove the old mower spark plug..  Check the gap on the new spark plug.  Use a specialized gap tool or a set of feel gauges to adjust the gap.  Refer to your manual for the correct gap.

Step 3: Change the spark plug

Install the new mower spark plug, being careful not to cross-thread the plug. You should be able to thread it in smoothly by hand for a few turns.

Step 4: Tighten the mower spark plug

Using the spark plug wrench, continue tightening. Make sure the mower spark plug is in tightly, but do not over-tighten it.

Step 5: Reattach the spark plug wire

Once you've replaced the lawn mower spark plug, reconnect the spark plug wire.

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