How To Change a Spark Plug on a Dirt Bike

Replacing a spark plug on your dirt bike is quick and easy. It’s something that needs to be done every now and then even though we’d honestly rather be only riding dirt bikes all the time.

Changing the spark plug on a dirt bike usually requires removing the gas tank, disconnecting the spark plug lead, and replacing the old spark plug with a new matching spark plug. In some dirt bikes, you can replace the spark plug without removing the gas tank.

In this article, we will cover:

It’s an easy job to change the spark plug on a dirt bike, especially if you follow these easy five-step instructions. So let’s get started!

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A hand holding a wrench and opening the spark plug on a dirt bike

Why and When To Change the Spark Plug

The spark plug gets contaminated over time. The carbon build-up may cause a weak spark resulting into rough idling or having difficulties with cold starts.

Changing the spark plug on a dirt bike is part of the regular bike maintenance and recommended every 40 hours of riding or so.

Typical symptoms related to a bad spark plug on a dirt bike or motorcycle includes:

  • Difficult cold starts
  • The dirt bike is idling rough
  • Motor is sputtering
  • Misfiring
  • Exhaust popping
  • Pinging or early detonation
  • Higher than normal fuel consumption

If you experience any of the above symptoms, it is time to replace the spark plug on your dirt bike or motorcycle to a new one.

How To Find a Replacement Spark Plug for Your Dirt Bike

Spark plugs on dirt bikes come in different types, sizes, threading and temperature settings. You have the options to buy copper, platinum and iridium spark plugs.

However, the model number stamped on the side of the spark plug is the one that matters. The spark plug model defines the temperature and resistance settings designed to your dirt bike or motorcycle and ensures proper fitment.

Each dirt bike will require a specific spark plug. You can find the spark plug model from your service manual or look at the side of the old spark plug for the exact spark plug model.

This NGK Resistor Sparkplug is a common spark plug for 2018 KTM 300 XC-W that also fits many other dirt bike models. You can find more spark plugs for your dirt bike here.

Tools Needed for Changing a Dirt Bike Spark Plug

You can use a normal wrench or an adjustable wrench to replace the old dirt bike spark plug. Sometimes the spark plug is hard to reach or at an angle where a special tool will help. In most cases the spark plug can be changed without taking the tank apart, but it usually requires using a shorter special spark plug tool.

The KTM spark plug removal tool is a handy tool that usually fits under the gas tank and makes the spark plug change quick and easy. Most manufacturers have similar short multi tools available.

Here are some popular dirt bike spark plug tools or wrenches:

  • KTM 4 in 1 Multi-size wrench. It is the wrench that comes with a new KTM or Husqvarna dirt bike tool kits and can be used to open most nuts in dirt bikes, including the spark plug. This KTM spark plug removal usually fits under the tank well.
  • Motion Pro 13/16″ Ratchet Spark Plug Wrench. This ratcheting wrench makes it easy to loosen the spark plug with the gas tank on. Fits standard 21mm size spark plugs.
  • 2-Piece Adjustable Wrench. This 2-piece adjustable wrench set works well to open any size spark plug. The shorter 6 inch wrench should fit under the gas tank.

How To Change a Spark Plug on a Dirt Bike in 5 Steps

Changing the spark plug will take you about 15 minutes. Time spent on the task varies depending on how easily you can access the top of the cylinder head area with tools. The only tools you will need are regular maintenance tools that usually come with the dirt bike tool kit.

Step 1: Clear Space To Access the Cylinder Head Area

Changing the spark plug on most dirt bikes can be performed with the gas tank on. However, getting your wrench fit well might be an issue.

The multi wrench that comes with many dirt bike toolkits should fit and have enough space to open the spark plug and retighten it safely. This works great when you need to change the spark plug trailside. But we recommend performing the spark plug swap at the same time with other maintenance tasks while you have the gas tank off the dirt bike.

A dirt bike standing on a center stand with the seat, gas tank and plastics removed
The gas tank, side plastic panels, and head exhaust pipe are removed for clear access to the cylinder head.

Having said that, let’s start by removing the gas tank and the dirt bike plastics that are holding the gas tank in place. You want a clear access to the cylinder head and to be able to have enough space for the wrench to fit well.

Step 2: Remove the Spark Plug Cap

Remove the rubber spark plug cap by grabbing it tightly and pulling it straight upwards. You can wiggle it if it appears to be stuck.

Once it comes loose, do not twist or pull the cap as it may disconnect from the lead wire and cause a weak or lost spark. Set it aside away from the spark plug. You can use a zip tie if needed to keep it out of the way.

If you have intermitted issues with the dirt bike and you suspect it might be related to ignition issues, check the spark plug lead wire thoroughly. Sometimes the plug may become loose from the lead wire and may cause a weak spark. To make sure it’s not loose, rotate the black rubber lead connector clockwise while pushing it inwards into the lead wire.

It is also a good idea to check the model of the old spark plug on your dirt bike. If you have any idling issues or similar issues described previously, the cause maybe a wrong model spark plug. Check the plug model against the service manual and replace with original spark plug to eliminate the spark plug related issues.

Step 3: Remove the Old Spark Plug

Use a closed-end wrench to carefully open the old spark plug by rotating counterclockwise. Once you break the spark plug loose, use your fingers to thread the old spark plug out.

Hands holding a wrench around a white spark plug on a dirt bike cylinder head and about to change the spark plug
The KTM spark plug removal tool is a handy tool that usually fits under the gas tank to remove the dirt bike spark plug.

The spark plug usually has a rubber seal preventing dirt build-up around the spark plug. You need to save it and reuse it on the new spark plug.

You can find replacement spark plugs for your dirt bike here.

Step 4: Change the Spark Plug Into a Matching New Spark Plug

Next, compare and make sure the new spark plug has the matching temperature setting and size as the old one. The text on the spark plug isolator, that is the white part, indicates the spark plug heat setting and they need to match.

Check your owners manual for the original recommended spark plug model.

A white spark plug threaded slightly in on a dirt bike cylinder head
A spark plug on a dirt bike being replaced with a matching new spark plug

Move the rubber seal or grommet from the old plug to the new plug. Thread the spark plug back in place by hand all the way in first.

Then snug it slightly with the wrench. DO NOT OVERTIGHTEN. A good thumb rule is to tighten the spark plug in by hand, then use the wrench and turn ONLY 1/8 of a turn.

Reinstall the spark plug cap by holding it tightly and pushing it straight down. You should hear an audible click and feel when the plug cap is in place.

Make sure the cap wiring is unobstructed and clear of the gas tank mounting areas. Use zip ties if necessary to fix it in a stable position.

Step 5: Finish the Gas Tank Assembly

Reinstall the gas tank and side plastic panels to finish the process of changing the spark plug on your dirt bike.

When reinstalling the gas tank, check that the spark plug lead wire and the throttle cable are not crimping under the gas tank mounting points. Sometimes there is not a lot of space between the gas tank and the frame around the mounting points and correctly routing the wires is extremely important in order to prevent future issues.


Change the spark plug on your dirt bike often into a fresh one, especially with two-stroke engines. It is a quick and easy way to prevent cold starting issues and resolve a rough idle.

Spark plugs are cheap to buy, so carry a spare one in your trail tool kit and you will be able to change the spark plug trailside should any issues occur.

Keep on firing!

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