Why Does My Dirt Bike Start But Then Keep Shutting Off?

Your dirt bike starts then shuts off. This is a frustrating issue. While it’s good that the bike will start, you have to figure out why it will not idle.

Luckily, there are a handful of common reasons this happens and a handful of easy solutions. We are here to help you figure out why your dirt bike starts then shuts off, so you can enjoy your adventures.

Why Your Dirt Bike Starts Then Shuts Off

Your dirt bike should be able to idle, whether it is a two-stroke or four-stroke bike. While a two-stroke bike might be a bit more choppy, it should run and stay running for a reasonable amount of time. If it immediately shuts off or dies after a short idle, here are a few common reasons.

Idle tuning and engine heat

You can and should adjust your idle to ensure your dirt bike stays running. If you set it too low, it will start, then shut off. Be aware that your dirt bike might need the engine to warm up more to function. Leaving the choke on a bit longer can keep the dirt bike running without needing more gas.

Weak spark

A weak spark can cause a dirt bike to start then stop. There are a few reasons for a weak spark, such as a fouled spark plug or one that is too old. In these situations, replacing the plug itself is a simple fix. A weak spark might also come from a bad spark plug wire, which necessitates replacing only the wire. The same holds true for a coil, which is also easy to replace.

Air filter issues

Unless your bike has good airflow, it is more likely to stop running after it starts. Check the air filter and clean it if it is dirty. Replace it if it’s falling apart. The box around the filter should be clean and free of obstructions.

An air leak can also cause engine issues, along with letting dirt and other foreign materials into the engine. Inspect for loose, cracked, or damaged parts and bolts. Double-check your gaskets and look for gaps in the intake.

Fuel problems

Your dirt bike might be getting enough good gas to get started but encounter fuel problems shortly after that. Old or dirty fuel is going to cause problems. Another potential issue is the air/fuel mixture, which could require carburetor tuning.

If tuning the carburetor with the fuel/air screw does not help, it could be a pilot jet scenario. A jet that is too big offers fuel that is too rich. This will start the bike but will not keep it running. A leaner, smaller jet replacement can help. You may also need to clean the pilot jet circuit along with the rest of your carburetor.

What about the fuel line? If it is kinked or pinched, the dirt bike might get enough gas to start but not enough to keep going. Look at the line and ensure there are no places where fuel might be getting caught.

Battery/stator

With stator problems, your dirt bike will start, but it will not charge to power the electrical system and battery. A voltmeter is all you need to test this theory. Check the battery with the engine and the power turned off. Anything lower than around 12.5 to 13 volts shows that you are having a battery problem. With the engine on, recheck the voltage. Rev it up and watch the voltage. If it does not go up, the stator is bad or you are looking at a connection issue.

Broken carburetor

Many of the parts we’ve considered ultimately connect to the carburetor, but sometimes it is the carburetor itself that is the problem. If you have run through every other potential reason your dirt bike is starting but not staying running, it might be the carb. One way to test it is to find a friend with a suitable, reliable carburetor. If you swap them out and your dirt bike is suddenly running correctly, you know that you need to replace your carburetor or figure out what’s wrong with it. Either way, this is likely a job for a mechanic.

A professional can also help you if you have come this far and still do not know why your dirt bike is starting but will not stay running. However, with regular maintenance and a good idea of the parts of a dirt bike that can cause problems, you can overcome many mechanical issues. Even if it necessitates some mechanical assistance, it’s worth it to enjoy the ride.