How to Replace a Spark Plug On a Lawn Mower

Replacing a lawn mower spark plug

In order to keep a lawn mower engine operating well it is recommended to replace the spark plug at least once per year. If the lawn mower is operated frequently it may be necessary to replace the spark plug more than once per year. A lawn mower has very few routine maintenance parts that need replacement, so replacing the spark plug is easy and very cheap so do not skip this need. This article will show you how to properly replace the spark plug in a lawn mower.

Things You Will Need

Spark plug gap tool

Spark plug socket

Replacement spark plug

Step 1

Old lawn mower spark plug Pull the spark plug wire boot off the existing spark plug that is currently in the motor. Just pull the boot back away from the engine to expose the existing plug. Write down the brand and model number of the spark plug. You will need this information to be able to find a replacement.

Step 2

New spark plug

Take the spark plug manufacturer name and model number to a home improvement store that sells lawnmowers, a lawnmower dealer, or an big box retail store. Either find an exact match in regards to manufacturer and plug number or look for the same spark plug from a different manufacturer. They will usually have a reference guide that cross references different manufacturer's spark plugs to find a match. If you like you can do a look up on one of the major spark plug manufacturer's web sites like autolite or NGK before you go to the store. You can also order the spark plug online although unless you buy in bulk, it would be as much to ship the item as the price.

Step 3

Using a spark plug socket, remove the existing spark plug from the engine by turning the plug counterclockwise. This may be different on some cheap Chinese mowers since they do not always follow US standards. Inspect the spark plug to see how much build up there is around the gap. This can tell you how the motor was firing. Throw the old spark plug away.

Step 4

Set the spark plug gap

Find the manual for your lawnmower or look online to find a manual. Determine the recommended gap for the spark plug. Using a gap tool, set the gap on the plug.

Step 5

Place a little new oil around the threads of the new spark plug. This will make it easier to tighten the new spark plug into the engine. It will also help to be able to remove the spark plug next time you need to change the plug.

Step 6

Insert the spark plug in the engine and, using a spark plug socket, rotate the wrench clockwise to tighten. This also may be different on some cheap Chinese mowers since they do not always follow US standards.

Step 7

Connect the spark plug wire boot onto the end of the new spark plug so it gets a good electrical connection. The lawn mower will be ready to go with the newly installed spark plug.

Tips & Warnings

Never replace the spark plug on a hot lawn mower.