How to Change the Spark Plug on a Lawn Mower

by Mike Palmer

A Bad vs Good Lawn Mower Spark Plug

Worn/Fouled Spark Plug vs. New Spark Plug

A dirty or worn spark plug can make your lawn mower hard to start, make your engine run rough and cause it to misfire. It can also be a symptom of other problems such as bad fuel, a carburetor that needs to be adjusted, or a dirty air filter.

How Often Should I change the Spark Plug on My Lawn Mower?

You should change the spark plug on your mower about once per mowing season or after about 100 hours of use.


What Tools Do I Need to Change a Mower Spark Plug?

Tools Needed for Changing Lawn Mower Spark Plug



Socket Wrench
Spark Plug Socket
Spark Plug Gap Gauge




Step-by-Step Instructions on How to Change Your Lawn Mower Spark Plug

Step 1: Move your lawn mower to a level surface so it won’t roll while you are working on it. Make sure the engine has cooled down before you start.

Step 2: Disconnect the spark plug wire.

Step 3: Loosen the spark plug by turning it counter-clockwise using your socket wrench (with the spark plug socket).

Step 4: Remove and discard the old spark plug.

Step 5: Verify the new spark plug you have is the correct one since many of them look alike. Double check with the engine manual if you are unsure.

Using Spark Plug Gap GaugeStep 6: Check and adjust the gap on the new spark plug using the Spark Plug Gap Gauge. Again, refer to the manual for your engine’s recommended gap on your spark plug.

Step 7: Screw in the new spark plug using your hand. Tighten the spark plug with the socket wrench, but don’t over-tighten.

Step 8: Re-attach the spark plug wire.

And that’s all there is to it!

Remember, changing the spark plug should be part of your regular lawn mower maintenance, along with oil change and mower blade sharpening.

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