9 Reasons Why My Dirt Bike Won’t Start & How to Fix?

Written by

James Stevens

Fact-checked by

Robert A. Verdin

Reasons why my dirtbike wont start

I was ready to hit the road for another adrenaline-fueled ride when all of a sudden, my 4-stroke dirt bike won’t start. This was a very frustrating ordeal because I was all pumped up for a day of fun and thrill.

Since most bike owners encounter a similar problem, there can be several reasons behind it. If you are currently in the same situation, here are possible reasons why my dirt bike won’t start.

Why Doesn’t My Dirt Bike Start?

The common reasons why a dirt bike may not start include:

  • Gas issues
  • Bad spark or faulty starter
  • Clogged fuel
  • Clogged air filter
  • Blocked carburetor jets
  • An air leak in the system
  • Damaged electrical connections
  • The choke not working properly
  • Low compression.

1. Gas issues.


Gas issues can be major causes for a dirt bike not starting. Check if the tank is empty or if the gasoline is old or discolored.

If the bike is not routinely used, gas can age and produce a varnish residue upon evaporation, weakening its combustion ability. This then clogs fuel injectors and other fuel system components.

Chemistry changes in gasoline start around thirty days after filling the tank; therefore, gas degrades and can lead to problems such as the bike not starting properly, reduced bike engine performance, and clogged fuel injectors.

  • How to fix it?

You can prevent this from happening by draining the gas if you plan to keep it in storage for more than 30 days.

Also, to make the gas cooler, especially during the summer, you can use a tank wrap taped underside of the gas tank.

2. Bad spark and a faulty starter.


If your 2-stroke dirt bike is not working, a faulty starter might be why. If your mini bike won’t start but the motorcycle has power but won’t turn over, the starter could again be the culprit. A faulty starter typically generates a clicking sound upon start-up or an engine turning on slowly.

Moreover, the battery can also be a reason. If the voltage is too low, there might need to be more amps to turn on a dirt bike.

  • How to fix it?

Check the spark plug and the battery. Remove the spark plugs and make sure that it is not damaged. It can be cleaned with a wire brush if it is dirty.

If the motorcycle shuts off while riding, checking the batteries for dirt bikes with an electric starter is necessary. Also, check the voltage to see if it is fully charged or not.

3. Clogged fuel


With a clogged fuel system, the dirt bike may not start since it restricts fuel from going to the engine.

In a fuel-injected or carburetor dirt bike, the clogging can be caused by various factors, including a malfunctioning fuel pump and a damaged or dirty carburetor or fuel injector.

Another reason can be the gas boiling over. When hot, the engine also gets too warm, boiling and spilling out the gas in the tank, picking up debris from the surrounding area, and pulling it into the carburetor or fuel line. The collected debris will cause a clog in the fuel system.

  • How to fix it?

You should clean the clogged fuel injector and try starting the bike again. Also, make sure you use high-quality fuel to prevent issues such as an unclean carburetor in the long run.

4. Clogged air filter


Clogged air filters restrict air entry which then interrupts the engine combustion process. When this happens, lesser air enters the engine, which disrupts fuel burning.

This means that fuel consumption increases because it is not being burnt, and more is necessary to produce power. Then, it will be difficult to start the dirt bike.

  • How to fix it?

Check the air or fuel filter. I can remove the air filter to check for debris and dirt caking. If it is too dirty, it has to be replaced.

You should inspect for loose or damaged parts and bolts, look for intake gaps and check the gaskets.

5. Blocked carburetor


The carburetor regulates the amount of fuel and air and then delivers it to the engine. Once this is blocked, the ratio of fuel and air is not balanced, resulting in an engine failure or a bad start.

If your dirt bike keeps shutting off or even starting, it might be due to blocked carburetor jets or fuel lines.

  • How to fix it?

Check carburetor jets once all minor checks are done to fix a dirt bike that won’t start. It can be removed and disassembled and checked for blockages. If it is damaged, you might have to replace it.

6. Air leak in the system


Fuel to air ratio in the engine must be the right amount for combustion. With an air leak, this ratio can be disturbed, and the engine cannot start properly, or your dirt bike won’t stay running.

  • How to fix it?

You need to check for air leaks in the engine, carburetor, and airbox for any visible cracks. Tightening any loose gaskets or bolts can also help prevent air leak problems.

7. Damaged electrical connections.


A Chinese dirt bike won’t start or any bike for that matter if electrical connections are damaged. This disrupts electrical flow between the ignition system and the battery, and other electrical parts of the bike.

  • How to fix it?

Examine the electrical connections. When inspecting for electrical disconnections, you must first disconnect the battery. Also, inspect if the wires are frayed, or the fuse is blown.

Furthermore, make sure the ignition and the starting relay are working well. You can also use a multimeter to check the voltage and continuity.

If after running for a while, it still stops and doesn’t turn on, you can call a mechanic or go to a shop nearby.

8. Choke is not properly working


If the choke does not work properly, your motorcycle won’t start after sitting on it. This mechanism restricts air that enters the carburetor allowing a better fuel-to-air mixture necessary for starting cold engines.

  • How to fix it?

Check if the choke is functioning well or not. Adjust the choke to fix a dirt bike that won’t start. You might need to inspect and replace if the choke no longer works properly.

9. Low compression


Dirt bikes have specific compressions for them to start properly and run smoothly. If a bike has a lower-than-normal compression, it may be difficult to start, runs roughly, backfires on deceleration, or completely loses power.

  • How to fix it

There are different ways to fix a 2- stroke and a 4-stroke dirt bike that won’t start.

A major reason for a low-compression engine is a top-end that is already worn out. Replacing the piston or piston rings can be a solution to rebuild the dirt bike’s top end.

Another way to fix this issue is to start with a compression test while ensuring the bike is clean and turning off the engine.

If leaking components such as the cylinder ring, cylinder head gasket, valves, and camshaft cause low compression, carefully change them.


Riding your bike can give you a thrill and satisfaction. If your bike doesn’t start like mine, these reasons can be the first thing you can look into.

It is easy to troubleshoot a dirt bike that does not start as long as the anatomy of the machine is well understood. With this article, I hope these reasons why my dirt bike won’t start can guide you in troubleshooting your motorcycle.

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James Stevens

James Stevens is an expert bike mechanic who knows everything from basic repairs to custom modifications. What sets him apart is his ability to explain complex concepts in a way that's easy to understand. Check out his content on Speedway if you need help with upgrades or modifications for your bike.