How to Fix a Dirt Bike: Troubleshooting and Maintenance

If you ride dirt bikes, knowing how to diagnose and fix starting and running issues is a good skill to have. 

This page will cover some of the basics of dirt bike troubleshooting and maintenance.

It’s a good idea to also learn how to clean a dirt bike so you’ll be able to keep everything tuned in ready to ride.

How to Fix a Dirt Bike

Once you understand how your motorcycle works, diagnosing and fixing problems becomes much easier. 

There are a few basic things that your dirt bikes requires to run properly, they are:

• Fuel. 
• Air flow & compression. 
• Spark. 

From there, you can break down any issue into distinct sections and parts that require further inspection.

For fuel, you’ll be focusing on your gas tank, petcock, fuel line, and carbs. 

For air flow and compressions, you’ll be looking at your air filter, cylinders, and exhaust. 

For spark, you’ll be checking your spark plugs, coils, battery, and ignition circuit. 

The best way to keep your dirt bike running properly is to practice regular maintenance and inspections. 

Follow your dirt bike’s service manual for maintenance and tune up procedures, and give a thorough inspection before and after you ride. 

Fuel

For fuel, you’ll need to confirm that gas is flowing properly from the tank through the carbs and into the combustion chamber. 

Work your way from the fuel, petcock, and inline filters, and fuel line to the carbs. 

If gas isn’t reaching your carbs, then you’ve got a clog somewhere between the tank and fuel line. 

If fuel reaches your carbs, but not the combustion chamber, you’ve likely got a dirty carburetor. 

Learn how to clean a dirt bike carburetor here. 

If your dirt bike is running poorly, it may be that your carbs are not tuned properly. You can learn more about troubleshooting carb issues and lean vs. rich running conditions here. 

Air

Next, you’ll want to confirm that the fuel circuit is getting the proper flow of air and there is enough compression in the combustion chamber. 

Ensure the air filter isn’t clogged and that your carbs are clean and properly adjusted. 

If you haven’t done so in a while, it may be time to change or clean your dirt bike’s air filter. 

If your dirt bike is old, the piston, rings, and cylinder walls may be too worn down. In this situation, the combustion chamber may not have adequate compression to complete or maintain the combustion cycle. 

Learn how to check the compression on your dirt bike engine here.

Spark

Finally, you’ll need to confirm that your ignition circuit and spark plug is creating a strong enough spark. 

First, make sure that your battery is fully charged. 

Next, confirm that the spark plug is set to the proper plug gap. 

Finally, you can check the spark by removing the spark plug from the engine, placing it on top of the engine and starting the bike. 

Visually inspect that there is a strong spark coming from the plug. 

If not, there may be an issue with the coil or your ignition system. 

Why Won’t My Dirt Bike Start?

Before you start taking your bike apart looking for major issues to fix, take some simple steps first if your dirt bike won’t start. 

The first things you should check if your dirt bike is not starting include:

• Check that the key and kill switch are in the correct position. 
• Check the the transmission is in neutral. 
• Confirm that there is fuel in the tank and the petcock is in the running position. 
• Make sure you are using fresh gasoline.
• Make sure that your battery is charged. 

If you’ve taken take of all the simple things and it still won’t start, you’ll need to move on to inspection of the major systems:

• Fuel. 
• Air.
• Spark. 

The most common cause of a no-start condition often comes down to the carburetor. 

Ensure your carb is clean and properly adjusted. 

If the bike is old, there may not be enough compression in the cylinder to start and stay running. 

Why is My Dirt Bike Leaking Gas?

A dirt bike leaking gas should not be ridden. 

Leaking gas can be dangerous, and gas getting into places it shouldn’t can cause damage. 

The most common causes of leaking gas are:

• Pinholes or cracks in the gas tank. 
• Leaking gaskets/seals in the petcock or fuel line. 
• Leaking gaskets/seals in the carbs. 
• Loose or improperly installed components within the fuel circuit. 
• Stuck carb float or float needle. 

Work your way through the fuel circuit and carbs to confirm where the leak is coming from. 

Why Does My Dirt Bike Backfire?

A backfire is a loud “pop” or “bang” from your exhaust. 

Backfires in your dirt bike is a symptom of improper tuning or the fuel/air ratio.

When running properly, the fuel and air mixture is supposed to combust and expel within the combustion chamber and through the exhaust. Backfire is caused by a secondary combustion within the exhaust when the mixture is off. 

Some of the most common causes of why your dirt bike is backfiring, include:

• A dirt carburetor. 
• A lean running condition (too much air).
• A rich condition (too much fuel).
• Improper ignition timing. 
• Aftermarket exhaust and carbs that haven’t been tuned for it. 
• Weak spark or fouled spark plugs. 
• Loose headers. 

To fix a backfire issue, you’ll need to determine what’s causing it. 

The best course of action is to:

• Make sure everything is properly tightened and installed. 
• Make sure all necessary gaskets are in good condition and properly aligned if you’ve recently rebuilt the engine. 
• Make sure the battery is fully charged. 
• Perform a full tune up and make any necessary adjustments. 
• Be sure to rejet and or readjust your carburetor if you made any changes to the air filter or exhaust. 

Dirt Bike Electronics & Ignitions

Problems with your dirt bike’s electrical components such as the battery, stator, or ignition coils can cause some major headaches. 

If you’ve confirmed that the fuel, air, and compression aren’t the problem, then it’s your electrical system that is the likely culprit of a no-start condition. 

In order to fix electrical problems on your dirt bike, you’ll need to work through the electrical system to find the faulty component. 

This includes:

• Testing the battery. 
• Checking the fuse. 
• Testing the dirt bike stator. 
• Testing the dirt bike coil. 
• Checking and cleaning the wiring and connections. 

To test electrical issues on your dirt bike, you’ll need a multimeter that can measure Ohms and voltage.

For more information, check out our guide on troubleshooting electrical and starting problems on your dirt bike and motorcycle charging systems. 

You can find a lot more dirt bike maintenance and repair guides here.