Why Does My Dirt Bike Only Runs On Choke – How to Repair It?


Sometimes, dirt bikes only run on choke, and when you turn it off, you will be unable to start your bike. If you wanna know why does a dirt bike only runs on choke,” then you are at the right place.

If a dirt bike runs with only the choke on, the reason behind this is the in choke on condition, rich mixture flow to the engine and the richer mixture becomes ideal as the engine’s usual operating fuel mixture. On the other hand, when the choke is off it supplies leaner mixture which is not enough to run a dirt bike. And hence when the choke is not on, the engine does not get enough fuel; rather than it gets too much air; therefore, it stops.

As you know, choke plays a vital role in a dirt bike or any motorbikes. Sometimes you may have noticed your bike dies when you turn the choke mode off.

There are different reasons for this, and you can fix it by yourself. But if you think riding a bike with a choke on, you’re gonna lose so many things.

Let me tell you how choke works and why do you need to fix the issue, and what will happen if you avoid it.

You can even ask the nearby motor mechanics; they will tell you the same. At my end, I have done my research work; here is what I have got information from my research.

How does Choke Works in a dirt bike?

What is a choke? If you are new to dirt bikes or any motorcycle, then it would be your question here.

A choke is like a small machine part of a bike that resists the airflow in an engine’s carburetor. It helps the engine to start even at a low temperature. A combination of the carburetor and the choke valve helps the bike to get enough air and fuel for a smooth start during cold weather. 

When you start your bike while it’s cold, turning on the choke is good. As choke will allow more fuel passage to the engine and tune the carburetor, the bike will start.

But, you are aware that every good thing has its bad habits too. Similarly, leaving the choke on while riding will no longer be beneficial, but how? we will talk about it next.  

What happens if you run your dirt bike with open choke?

If you ignore the choke and keep riding your dirt bike, this will make a significant loss. When you leave your choke on, the engine starts burning more fuel.

It will result in more oil consumption, so you need a fuel station to fill the tank again. In the winter seasons, the engine needs more fuel at starting, but when this is ready to get a ride, be assured the choke is off. 

If you leave your choke on, the bike engine will be addicted to it. And as a result, your bike will be under the control of a choke.

Also, more fuel starts burning, which produces more carbon that is not good for the environment. 

Why does a dirt bike only runs on choke?

Finally, we have come to the point where we will discuss, why does a dirt bike bike only runs on choke?

Here, you will see the most commonly occurring factors and how to resolve the issues at the same time. 

1. Dirty Air Filter

If the air filters are dirty, it will create problem in airflow.

When this happens, the engine starts burning more fuel, and hence it needs more fuel which is only possible when the choke is on.

Gradually, your bike only runs when the choke is on and shuts down according to choke steps. 

How to clean a dirty air filter?

If you find that the air filter is dirty, then follow the steps to clean it:

  • Please remove it from the rag, and don’t forget to check the airbox area is cleaned. 
  • Please put it in a bucket of warm water with washing powder. Leave it for 20 minutes at least. 
  • Now, squeeze the water and let it dry till that cleans the airbox full of dust or dirt. 
  • Once the filter is dried, oiling it. When it soaks the oil, apply grease around the rim of the filter. At last, put it back to its place. 

In this manner, you can check air filters and clean them as well. Now, we are moving to the next point. If there is no issue with your air filter, the next one may be beneficial. 

2. Wrong Float Height

If you have set the lousy level of float height, this will affect fuel flow. The float is placed at the top of the float bowl.

If you set it too high, fuel will flow more even if it damages the engine.

And if it is set too low, your bike doesn’t start. That’s why in such cases, the engine needs more fuel and runs only on chokes. 

How to adjust float Height?

Now you want to know which height is perfect that will not damage any internal part. Let’s see the procedure:

  • Take off the carb and drain it so that you can access the float easily. 
  • Now, remove the float bowl and use vernier calipers to measure float height. 
  • Measure the float through the top of the carb as such that floats fall back enough to close the float valve without pressing the float valve spring. You can find the manual as well for more details. 

If you still didn’t get the answer to ‘Why Does My Dirt Bike Only Runs On Choke?’ Have some patience, and maybe the next one will be your solution. 

3. Dirty Carburettor

If your bike runs only on choke and releases black smoke from its exhausted area.

This would be a sign of a dirty carburetor. Yeah, when the carburetor is dirty, it distorts the ratio of air and fuel, and as a result, more fuel will be released into the engine.

More fuel means more burning, and for more fuel, the choke is needed to be on. 

How to Clean Dirty Carburettor?

If black smoke is coming out from the exhausted area, it means you need to clean the carburetor, don’t take too much stress with just a few steps; you can clean it your own:

  • Remove the carburetor carefully as it will turn off the valve of the fuel tank. 
  • When you successfully take off it, separate the float, the bottom part of a carburetor. It would be best if you did so as cleaning the carburetor will be easier. 
  • Now, it’s time to separate the pilot jet, a part of the carburetor which is long and skinny by look. 
  • At the last step before the cleaning process, remove the air screw and idle screw too. 
  • Now, clean the parts using spraying carb and choke cleaner. Once you are done with cleaning, reset the components in the reverse way as you separated them. 

You have seen how to fix a dirty carburetor, but did you find it helpful or not.

If you have cleaned air filters, carburetor and also adjusted the float height as mentioned above, but nothing works. In such a case, you need to check the pilot jet at the last time. 

4. Blocked Pilot Jet

You might have heard that jetting a bike will charge it up. It’s nothing, just changing the size of the hole by adjusting the needles. These needles shift the ratio of air and fuel.

But, if the pilot jet is blocked, your bike will run lean and slowly- slowly start taking more power. Usually, a pilot jet is used to start the dirt bike; when it is jammed, a choke is needed.

That’s why this point is also a part of ‘ Why Does My Dirt Bike Runs On Choke.’ Let’s see how to maintain a pilot jet.

How to fix blocked pilot Jet?

You can unblock the pilot jet in different ways, either by removing the complete carburetor or just removing the bottom float part. 

  • Remove the carburetor as we have discussed in the previous point. One by one, you will need to remove the jet too. 
  • Now, spray some carburetor cleaners and wait for a while. Then again, spray the same amount. Now, please wait for a few minutes until it recovers completely. 
  • Reset the float bowl by attaching the pilot jet. Take a ride to know if it works or not. 

We have dealt with one more point about blocked pilot jets as I shared all possible ways, which may be one reason behind the lousy choking. But the last one still keeps you in the same situation. 

5. Long time

I know it sounds crazy that how long time steady mode can make your dirt bike worse.

If you haven’t used your bike for a long time, in that case, it only runs on choke for a few days.

When you leave your bike for a long time, the entire tank will evaporate and also block all the valves.

You can solve this issue before riding, clean all the system parts such as air filters, carburetors, pilot jets, and float bowls, too, in the similar way I told you earlier. And then feed it with a perfect ratio of air and fuel. 

I discussed all the crucial points to sort out the issue. Any one of them will help know ‘why does my dirt bike only run on choke.’  

Note: If nothing works at all, even cleaning the whole bike. It would be best if you visited the nearby motor mechanics centers. They have more knowledge and ideas on fixing any issue or problem (like dirt bike dragging) related to dirt bikes. Keeping and riding a dirt bike is easy, but it will be a headache if you don’t maintain it in an exemplary manner. 

Conclusion

In this article I have explained why does ay dirt bike only runs when choke is on.

I have also shared the research I have done about how to fix this issue. I guess this post was fruitful for you.

If you like our post, then don’t forget to comment. If you want more details or fix the issues related to dirt bikes, subscribe to our newsletter.  

Thomas A. Talley

I’m Thomas. Since childhood, I am fond of bikes and hence dirt bikes are my passion now. Ever since then, I’ve been giving advice to the beginners and this has become my hobby.

Recent Posts