Replacing your spark plugs is a simple, cheap, and quick way to keep any machine running smoothly and efficiently. Whether you have a brush mower, lawn mower, stump grinder, or homemade whoozeywhatsit, if it has a combustion engine, it has spark plugs. You can easily replace your own spark plugs on both manual- and electric-start engines.

How do you know when your spark plugs need replacing?

On an manual-start engine, you’ll know that they need replacing if you find yourself having to yank and yank and yank to get the engine started. Or, if once you get it started, it often sputters and stops running. In an electric-start engine, you may find that it doesn’t start on the first try, or doesn’t stay running once you’ve started it. As part of your regular maintenance of any machine, you should replace your spark plugs about once a year.

How to replace your spark plugs:

Thankfully, spark plugs are inexpensive to purchase and simple to replace. Here’s how to go about it:

1. Locate the spark plug. It can be found on the front or side of your engine, and looks like the image at left.

2. Remove the wire. Pull the plastic or rubber wire out of the spark plug.

3. Remove the spark plug. Use a deep-set socket wrench to unscrew the spark plug from its housing.

4. Look at the reference numbers. Printed on the porcelain part of the plug you’ll find a reference number. Take that number to your local hardware store to ensure that you get a replacement plug that will fit in your engine.

5. Check the gap. Spark plugs function best when the gap between the two metal components at the bottom is a very specific distance. This is because a spark of electricity will go across this gap, igniting the compressed fuel in your engine to get it started. The ideal gap distance will differ depending on your engine model, but you can check your owner’s manual for the ideal gap for your spark plug. Use a spark plug gapping tool to measure the gap on your new spark plug before you install it. If it’s too narrow, you risk burning the end of the plug or detonating the fuel prematurely. If it’s too wide, you will have trouble getting the spark to cross the gap, making the engine difficult to start.

6. Set the gap. If your new spark plug’s gap is too wide, gently tap it on a hard surface to bend it a bit closer to the stationary metal piece. Then, test it again with your gapping tool. If it’s too narrow, gently bend it outward and retest.

7. Install the new plug. Screw the new spark plug into the port on your lawn mower engine, tightening it down with your socket wrench. Be sure to make sure it’s firmly in place but not excessively tight. Finally, replace the wire.

Changing the spark plugs on your DR machine? Make it part of a full engine tune-up for your DR RapidFire Log Splitter, DR Dual-Action Log Splitter, DR Chipper, DR Field and Brush Mower, or DR Trimmer/Mower.