Is Your Dirt Bike Missing its Spark? Here’s What To Do

Is your dirt bike missing its spark, otherwise known as misfiring? This problem can be an easy one to diagnose or one that can keep you baffled for hours! Once you have checked the obvious, it sometimes pays to investigate the obscure! You may be surprised at what you find!

There are a few reasons why your dirt bike might be missing a spark or misfire. Some possible reasons include a bad spark plug, a bad spark plug lead connection, a blocked fuel line, a block fuel filter, a carburetor not functioning properly, or dirty fuel.

The best strategy to follow when trying to solve this problem is to start with the simplest and most obvious first. We will follow that strategy here in discussing the potential problems from the easiest and most obvious to the more difficult and more obscure!

Let’s get started diagnosing why your dirt bike is missing its spark!

Bad spark plug

This is the most obvious choice to start looking at as a potential problem. Spark plugs are considered a consumable and need to be replaced periodically. After many hours delivering a spark, they can degrade and no longer produce an efficient spark.

This can be the result of buildup on the electrodes of the spark plug and can be remedied quite simply by removing the spark plug and cleaning both electrodes with some emery cloth.

Another reason for the lack of spark could be the gap between the electrodes is incorrect. It may be too small, or too wide, either instance could cause erratic sparking and cause your dirt bike to misfire!

A set of feeler gauges is necessary to set the gap correctly and don’t forget to find out the correct gap for your plugs from the manufacturer.

Sometimes the lack of spark could be a result of a problem that is difficult to diagnose with the naked eye. I have encountered instances where the electrode was cracked, but the crack was not visible on inspection. However under the intense heat in the engine, the crack opens up, causing a misfire problem for your dirt bike!

The Spark Plug Lead

Following the electrical path of the sparking system, the next easiest option to check is the spark plug lead. This lead sends the DC voltage from the coil (full name is the ignition coil) through to the plug and generates the spark as the voltage jumps across the spark plug gap.

Check the end that connects onto the spark plug to make sure it is making a proper connection, and likewise check the other end to make sure it is connecting to the coil correctly.

Another problem to bear in mind is one of those more obscure issues. It is not something that is not immediately identifiable with the eye. The cable itself may be faulty. A break in the cable may cause an intermittent connection, resulting in the misfire. The best way to diagnose this fault is with an electrical multimeter.

Could the coil be a potential problem? If you are experiencing misfiring across all cylinders, or the bike not starting at all, it could be a faulty coil. However, if the misfiring is localized to a single cylinder, it is unlikely to be the coil causing the problem.

Fuel Line

Moving through the list of potential reasons why your dirt bike is missing its spark, the next potential problem area is the fuel delivery system.

The first and easiest item to check in this system is the fuel line. Check to see that the fuel is flowing freely through the line and that the line is not blocked.

Wear and tear of the fuel line in the form of cracking may cause fuel to leak or air bubbles to form in the pipe. This may lead to misfiring, but can easily be remedied by replacing the fuel pipe.

Fuel Filter

Dirt bikes by their very nature are used in dusty, muddy environments. It is quite conceivable that your dirt bike’s fuel filter could have some dirt or debris that is clogging it up. This will prevent the free flow of fuel through the filter and may cause the misfiring issue you are experiencing.

The simplest solution is to remove the clogged filter and replace it with a new one. If, however, you are out at the track and don’t have a spare filter, there is another option you can try. You can dismantle the fuel filter and try to wash it out using some fuel from your tank. This may dislodge whatever is blocking the filter and allow for the free flow of fuel again. This method is not a guaranteed fix, and may only be a temporary fix, but it may get you up and running again for a day on the track!

You should then replace your fuel filter as soon as possible to make sure you have the best possible fuel flow for your engine.


The other culprit in the fuel delivery system that could cause your misfiring malady is a carburetor that is not functioning properly. The causes for this could be many, from a bent needle and seat assembly to a broken valve.

This type of problem normally needs expert care, where the carb needs to be stripped, cleaned, and serviced. This is probably not a job that can be done at the track but will have to wait till you get your dirt bike home.

The other issue that could cause a problem in the carburetor and the fuel filter relates to our next topic, dirty fuel.

Dirty Fuel

Once again, due to the environment that dirt bikes are used in, dirty fuel could be a real possibility. There could be various reasons for dirt in the fuel. Many people take additional fuel to the track in containers. The container may have become contaminated with dust from the track environment, or the lid not closed properly allowing dust and dirt to enter the fuel.

This dirt could enter the fuel system of your dirt bike and cause problems in the functioning of the carburetor, or cause blockages in the fuel filter.

Another possible area for contaminants to enter the fuel system could be from your bikes fuel tank. With the dusty and dirty conditions of off-road riding, an ill-fitting fuel cap could allow dirt to enter the fuel. This can result in the problems we have discussed and potentially cause your dirt bike to miss its spark.

I have even heard of a problem where a random leaf managed to get into a fuel tank and periodically blocked the flow of fuel out of the tank. This type of problem can be difficult to troubleshoot and the leaf moves around with the movement of the bike and the flow of the fuel.

Generally, the only way to fix a dirty fuel problem is a complete flush of the fuel system of your dirt bike. It can be a lengthy process, stripping each section of the fuel delivery system and cleaning it out. You will need to determine the source of the contaminant to make sure it does not clog the system once you put it all back together again!


In conclusion, please sure to go through the list of possible reasons why your dirt bike is missing a spark or misfiring, and remedy the problem accordingly in order to get back to the track in no time.

For any doubts or queries about your dirt bike and off-road adventures, be sure to check out this space for all the advice, tips, tricks, and hacks you need to make the most out of your off-roading adventures.

Happy dirt biking!

Louis Pretorius

As an amateur off-road enthusiast, I have always been drawn to outdoor adventure. I have decided to share all of my learning experiences with you as I dig a little deeper into my new-found passion and wonderful world of off-roading. My mission is to create the Ultimate Off-roading space on the internet in the process. Stay safe and happy Off-Roading!

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