Why Won’t My Dirt Bike Start : All Fixes

Why Won’t My Dirt Bike Start : All Fixes

When you want to go for a relaxing ride or an exciting rip around the track there isn’t anything more frustrating than when your bike won’t start. Figuring out what the problem is and then fixing it can be intimidating, and it’s easy to be overwhelmed if you don’t know where to start. Fortunately, we’ve put together this handy guide of the most common reasons why your bike won’t start, as well as the solutions. 

Now let’s look at the problems that can stop your bike from starting, and find the solutions that will get you back on the road. 

Why Won’t My Dirt Bike Start?

Several things can keep your dirt bike from starting up, but they are all based on a lack of one or more critical components in the combustion process. In order to run, an engine requires Air, Fuel, Compression, and Spark. If any one or more of these things is compromised, your bike simply won’t run. 

Why Won’t My Dirt Bike Start

Sometimes issues come up due to a simple maintenance oversight, while other times there is a greater problem at play. In this section we’ll look at the potential causes:

No Gas or Bad Gas

If your bike doesn’t have fuel, or can’t burn the fuel it has, it won’t run. If the tank is empty, your problem is obvious. If the tank is full and it still isn’t starting, check on how old the gas that’s in the tank is. Gasoline loses its potency as it ages, and creates a varnish. When that happens, not only will the old gas stop the bike from running, but it can cause other issues all through your fuel system. It’s a good practice to flush the tank and replace the old gas before trying to start the bike, especially if it’s been sitting for a very long time. 

Dead Battery

The battery is important for your lights and accessories, but is also critical to the starter motor. If the battery doesn’t have enough charge to run this component, the bike isn’t going anywhere. 

Dirt Bike Battery

Like gas, batteries age and can go bad over time. You can check the battery’s charge with a voltmeter, or simply charge the battery and try to start the bike again. If the bike starts right up after the battery’s gotten a charge, then your problem, and possibly the solution, is right there for you. 

Batteries have a shelf life, and replacing them every few years should be considered routine maintenance. If you ride infrequently, it is also a good idea to leave your battery on a tender.

Clogged and Dirty Air Filter

Good airflow is critical to any engine, and dirt bikes aren’t an exception. If your intake is blocked and the engine can’t breathe the air-fuel ratio will suffer and the bike won’t start. 

Most air filters are positioned for easy removal for the purpose of replacement or cleaning. If the air filter is so dirty that it’s keeping the bike from starting, it will be the kind of thing you can see once you’re holding it in your hands. If the air filter is the problem, cleaning or replacing it will solve your problems. 

Bad Spark Plugs

Your spark plugs are responsible for igniting the fuel in the engine and producing power. If they can’t reliably perform this function then there’s no explosion, and therefore no power. 

You can test a spark plug by removing it from the bike and holding the plug against the head of the engine. Remember to hold the plug by the rubber boot to avoid getting shocked. When you turn the engine over you should spot a spark arcing from the tip of the plug to the engine. This is referred to as “the spark test”. 

Clogged Fuel System (Carburetor or Injectors)

Just like an air filter, your fuel system can get clogged and fail to deliver enough gas to the engine. Without the right amount of fuel the bike’s engine will not function. 

You can figure out if your engine isn’t getting gas by dropping gas or starter fluid down the spark plug hole and then trying to start the bike. This bypasses the fuel delivery system entirely.  If it fires right up, that’s a sure sign that your bike isn’t getting enough fuel. This means that it’s time to do some carburetor maintenance (if your bike is carbureted) or replace your injectors (if the bike is fuel-injected). 

Cleaning the gunk and other buildup in your bike’s engine can affect your bike’s mileage and performance. You need the carb cleaner for it. Want to know how to make homemade card cleaner for your motorcycle? Check out our guide on it!

Low Compression

If your engine cannot achieve the level of compression necessary, the fuel and air in the cylinder will not create the explosion that drives the engine and produces power. 

Checking for low compression will require a compression tester. Your bike’s service manual will have a compression value that the engine should be running at, and if the test comes up lower than that, you’ve found your problem. 

This is one of the processes that you can do yourself, or you can take the bike to a certified mechanic to have it done. Simply having the compression tested is not typically an expensive service, but it can be an indicator of serious issues that can be very difficult and expensive to address. But currently there are many dirt bikes with powerband are available in the market.

What to do When Your Dirt Bike Doesn’t Start

Now that we’ve examined the possible causes for the problem, it’s time to get to work on correcting them. At this point you should have identified what the problem is. As pointed out, your bike needs Air, Fuel, Compression, and Spark in order to run, and the problems that could stop it from firing up all hinder one or more of these steps. 

What to do When Your Dirt Bike Doesn’t Start

Here we’ll break down the solutions by their simplicity. 

Refill, Recharge, and Clean

If your bike is out of gas, the battery has simply been run dead, or if the air filter is filthy it’s time to do some routine maintenance. These issues are things you’ll usually be dealing with long before they keep the bike from starting, but occasionally they will become problematic without warning. 

Gas Tank

For an empty gas tank, the obvious solution is to fill it up! 

  • Remember that a higher compression engine will run better with higher octane fuel. 
  • Keep in mind that fuel will age wherever you store it. 
  • Do not use gas that’s been sitting around for a long time, and if your motorcycle uses a 2-stroke engine. 
  • Always pre-mix your fuel to make sure the internal components are properly lubricated.  


Hooking your battery up to a charger will take some time, but if it has run out of charge, this is a simple solution. 

  • The battery powers all of the electronics onboard, and most importantly, runs the starter motor. 
  • If the battery won’t hold its charge, then replacing it is a simple matter of finding the battery that your bike needs. 
  • Remember that batteries do wear out over a few years.  Keeping a fresh one installed should be considered simple maintenance. 

Air Filter

Once you’ve determined that your motorcycle’s air filter is dirty:

  • Rinse the filter out, or to replace it entirely. Air filters are meant to be replaced periodically, roughly every 10,000 to 15,000 miles. 
  • If your filter is new but very dirty, take a moment to rinse out the outside and inside with a garden hose and then let the filter dry before putting it back on the bike. 
  • If you’re at or past that 10,000 mile mark, discard the old filter and replace it with a brand new one. 

You can also read this article on Best Motorcycle Oil Filters by Bikers Rights.

Plugs and Carburetors

This next round of repairs is a little more involved, but still something that you should be able to do on your own without much difficulty. 

Spark Plugs

To replace your spark plugs you’ll need a specific type of socket set designed for removing spark plugs.

  • You will remove the rubber boot over the plug, then use your socket to remove and then replace each spark plug. 
  • When you’re tightening down your spark plugs you should refer to your service manual for the correct torque measurement so that you don’t over tighten the plug, or install it too loosely. 
  • Once the plug is in, replace the boot and repeat for each cylinder. 


When your carburetor needs cleaning, there are two ways to go about the task. In both cases you will be removing the air filter, so now would be a good time to clean that component as well! 

For more minor issues with the carburetor:

  • You can spray carb cleaner into the carburetor without removing it from the bike. This is best done while the engine is running. 
  • However, and if the bike is not functioning then this method will not be an option. 

Removing and completely cleaning the entire carburetor is a more involved process, and it is the first task where consulting a mechanic is a good idea. The carburetor is absolutely critical to your bike’s operation, as it delivers fuel to the combustion chamber. If you are not confident or experienced in working with such an important part of your motorcycle, let a trained professional handle this step for you. 

Take it to the Shop

This is certainly not the most popular option, but definitely the safest when it comes to getting your bike running perfectly again. In some situations the problem demands a fix that involves diving elbows deep into the complex machinery that makes up your favorite dirt bike. You will want to go straight to this option if the problem you found involves low compression, clogged or damaged fuel injectors, or if you are not comfortable or experienced working with the bike’s carburetor yourself. 

Frequently Asked Questions

How do you start a dirt bike that has been sitting?

If your bike has been sitting for a long time, the first thing to do is check the charge of the battery, flush the fuel tank and replace it with new gas, and do an oil change. Following those steps, make sure the brakes, chain, forks and tires are in decent shape, clean the carburetor if it is carbureted and prime the engine before attempting to start the bike. 

What happens if you put regular gas in a 2-stroke Dirt Bike?

2-Stroke engines do not have separate reservoirs for their oil, and so they rely on the fuel system to keep them lubricated. Filling up the bike with fuel that hasn’t had oil mixed into it is functionally similar to running a 4-stroke engine with little or no oil, and carries the risk of catastrophic damage to the internal components of the engine. 

What causes a 2-stroke engine not to start?

While a 2-stroke engine has fewer steps to the process of producing power, it still requires the same components and is therefore still affected by the loss of those components in the same way. A lack of airflow, spark, fuel, or compression will cause a 2-stroke engine not to start no differently than a 4-stroke engine. 


In this article we’ve looked at several problems that can cause your dirt bike not to start. While there are many different parts that can wear out or be damaged so that the engine doesn’t start, always remember that it all comes down to one out of the four critical components of the engine’s operation: Air, Fuel, Spark, and Compression. 

As long as you keep those factors in mind, finding the problem and the solution is far less intimidating than it may seem at first. Even if the problem isn’t something you can tackle on your own, understanding what’s going on will save you time and money that you might otherwise be wasting trying to chase it down, and that’s time and money that can be spent on many more afternoons at the track or on the road!

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Ryan Christian

My lifelong love of everything on wheels began with a dusty old scooter and a set of second hand wrenches. Since then I’ve spent every moment I can spare finding new dirt paths, winding country roads, and long open highways. I write to share my passion with other enthusiasts, and maybe inspire one or two new ones along the way!