A lawn mower spark plug gap should have a standard distance ranging between 0.02 to 0.035 inches. A lawn mower should have a spark plug that is well-maintained to avoid problems.

How Do You Gap a Lawn Mower Spark Plug

In order to have the correct spark plug distance, we’ll go through three easy steps to have your lawn mower spark plug properly gapped.

How Do You Gap a Lawn Mower Spark Plug? 3 Simple Steps

💥 You can gap a lawn mower spark plug in three easy steps: Determine the recommended spark plug’s gap, measure the current gap, and adjust it accordingly. When it comes to lawn mower spark plugs or any small engine that has spark plugs, it is always best to keep them properly maintained.


This includes adjusting the spark plug gap and making sure that there is an appropriate distance between electrodes. Follow the steps below to successfully gap your lawn mower’s spark plug.

1. Determine the Recommended Spark Plug’s Gap

Read the owner’s manual of your lawn mower. Based on the recommended engine spark plugs, you’ll also be able to determine the model. This will come in handy whenever you need to make any lawn mower spark plug replacements.

Determine the Recommended Spark Plug’s Gap

As mentioned, lawn mower spark plugs typically need a gap between a range of 0.02 to 0.035 inches. Most spark plug gap distances require 0.03 inches. It is important that the spark plug gap size be as accurate as possible for the lawn mower to function properly.

Don’t worry if you can’t find the owner’s manual. Simply look for your lawn mower’s model number and use that as a reference to check for the spark plug specifications . You can do this online, with a small engine mechanic shop, or at the hardware depot where you purchased your unit from.

2. Measure Your Current Spark Plug’s Gap

In order to determine the measurement of the spark plug’s gap, you’ll need the help of one of these gapping tools. You can choose from a feeler gauge, a wire gap tool, or a coin gap tool to help you measure the distance.

Measure Your Current Spark Plug’s Gap

If you don’t have any of these and are looking to purchase, here is what you need to know about each type of gap-measuring tool:

  • Feeler gauges are the most gentle on the electrodes of your lawn mower’s spark plug. They can also be used to determine other mechanical measuring needs. However, they can be expensive.
  • Wire gap tools function similarly to feeler gauges, except that they are more circular with longer extensions to measure the gap. Wire gap tools are meant to be used on spark plugs and are quite easy to find.
  • Coin gap tools also have similar functions to feeler gauges and wire gap tools. However, they can easily damage the center electrode of the spark plug. It is quite affordable and easy to find, although it will require a careful touch.

3. Adjust the Spark Plug’s Gap Accordingly

Adjust the Spark Plug’s Gap Accordingly

  • Based on the results of your measurement, you’ll need to make the proper adjustments to the gap between the electrodes of your spark plug. Each of the tools mentioned has a hole or a slot that you can use to correct the grounded electrode gently.
  • Be gentle when you set your tool on the curved grounded electrode. Ensure that you are not applying pressure or touching the center electrode underneath.
  • Once in this position, slightly bend the grounded electrode to a distance that is appropriate, which is typically 0.03 inches. You’ll need to be careful as you can easily snap off the electrode if you apply too much force.
  • After bending the grounded electrode, measure the gap. This helps you see if you still need adjusting. However, if you managed to get it right the first time, then you can just stop here.
  • If you were not able to set the right gap between your spark plug, then you’ll need to adjust accordingly. You should eventually end up with the exact gap width based on your feeler gauge, wire gap tool, or coin gap tool.

The Importance of Gaps in Spark Plugs

Spark plugs ignite the fuel and air by initiating a spark. This provides enough energy to power internal combustion engines which are typically found in automotive models. The gap between the spark plug is found between the ground electrode and the center electrode.

These two parts can be found at the very tip of your lawn mower’s spark plug.

– Where the center electrode is located

On the other hand, you can easily spot the ground electrode. It is a metal piece that is slightly curved and runs from the threaded length of the spark plug.

Where the center electrode is located

The center electrode is found sticking out in the spark plug’s middle but still under the curved metal piece.

– Where does the arcing take place?

The gap between the two electrodes of a spark plug is where the arcing, or sparking, initiates. This means that the proper voltage will provide the right fuel ignition, causing the engine to run on the resulting combustion.

Where does the arcing take place

Without this gap, sparks would not be possible for fuel ignition and combustion. Thus, the correct gap is essential to making engines run.

– Deterioration of spark plugs

However, it should also be noted that spark plugs can break down as time goes by. This deterioration can also be a cause of any gap increase. This makes the spark plug unable to produce sparks for ignition.

Deterioration of spark plugs

On the other hand, if the gap is too small, it is still a problem. Despite the consistent presence of sparks, the thin gap will not provide enough room for the fuel and air to ignite and combust.

The Truth About Pre-gapped Spark Plugs

Some manufacturers will label their spark plugs as pre-gapped. The labeling encourages people to assume that the gap is accurately distanced. However, not all spark plugs will have the proper gap distance. Some will have wider gaps, while others will have narrower distances.

The inconsistencies can be caused by a lot of factors, such as friction with other spark plugs during transportation. These logistical activities can be one of the causes for the gap to narrow or widen.

This is why it is recommended to always check the gap between the spark plug prior to installation. Doing so will help you from reinstalling your spark plug frequently to check for the right gap distance.

Signs That You Need to Gap Your Spark Plug Correctly

As time goes by, your spark plug can slowly break down and wear out. This can lead to the gap between the electrodes of your spark plug to widen. When this happens, your lawn mower will not function correctly. Here are some signs when you need to correct the gap in your spark plug:

  • The engine of your lawn mower keeps on misfiring.
  • You have trouble starting your lawn mower.
  • The lawn mower runs out of fuel quicker than before.
  • Your lawn mower shakes or bounces when it’s turned on but idle.

Spark plugs are typically found on the side or the back of your lawn mower’s engine. Generally, a wire is attached to it. To be sure, check your owner’s manual.

If you are not in possession of the owner’s manual, you can always get the model number and type of your lawn mower. Use the information to search online. Alternatively, you can always inquire at the store where you purchased your lawn mower.

When purchasing spark plugs, it is always best to stock at least one or two at home. This will help you replace any damaged ones as quickly as you can. Keeping a few extra ones on hand will go a long way to making the most of your time.

– Removing and Replacing Your Spark Plug

Removing and Replacing Your Spark Plug

  • Once you’ve located the spark plug for your lawn mower, check to see if it is damaged or dirty. If it’s damaged, you can replace it. If it’s dirty, you can either clean it or replace it. In the past, spark plugs were expensive. Hence, people tend to clean them first before they think of replacing them. Now, spark plugs are more affordable so replacement is a better option.
  • To remove the spark plug, simply pull off the wire at the top of the spark plug. Look for a spark plug wrench and use it to latch onto the spark plug. Turn counterclockwise to loosen the spark plug and then remove it.
  • Prior to replacing the spark plug, ensure that the gap is correctly spaced. To install it, simply place the spark plug into its slot. Use the wrench to turn the spark plug clockwise to tighten it.

Frequently Asked Questions

– Do All Lawn Mowers Require the Same Spark Plugs?

Not all lawn mowers require the same spark plugs. Each model can require a specific model. Since each engine model can only fit a specific spark plug, using the incorrect ones can damage the lawn mower. This is why you should always ensure you are using the right spark plug model.

– How Often Should I Change the Spark Plugs in My Lawn Mower?

You should, ideally, change the spark plug in your lawn mower after every 25 hours of usage. Alternatively, you can replace them every season. However, if your lawn mower shows the signs of a damaged spark plug, it is time to install a new one.

– Is It Okay To Clean Used Spark Plugs in Order To Reuse Them?

It is okay to clean used spark plugs in order to reuse them. Although, it may not function as well as a new one. If you notice that your spark plug is too dirty or too worn, it’s better to replace it.


The lawn mower spark plug gap can be considered an important factor to keep the engine in tip-top condition. Let’s review what we’ve learned so far:

  • Ideally, the gap between the electrodes of a spark plug should be from 0.02 to 0.035 inches, with 0.03 inches being the most typical.
  • Correcting the gap distance of your lawn mower’s spark plug requires simple tools and a steady, gentle touch.
  • When your lawn mower has trouble starting and functioning, or even shakes when idle, it may be time to replace its spark plug.
  • Spark plugs should be replaced every 25 hours of usage, every season, or on occasions when it is damaged and unable to function properly.
  • It’s always best to check the gap of spark plugs, even when they are new since they can still be prone to having distances that are too narrow or too wide.

Now that you know the simple steps to fix the gap between the electrodes of your spark plug, you can rest easy if your lawn mower decides to malfunction. Simply remember to learn the model of your spark plug, stock some at home, and install them when the time comes!

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