Why Does My Dirt Bike Not Accelerate?

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Dirt bikes are well-known for their break-neck speeds and exhilarating experience to the riders.  These two factors allow you to make your riding fun, exciting and quite fulfilling. To achieve any of these feats, your bike must accelerate steadily to the velocity of your choice.

But it can be frustrating when it turns out that your dirt bike is not accelerating as you would wish. However much you try to make it increase the speed it still loses power and eventually slows down or stalls. So, what do you think might be the cause of your motorbike not accelerating?

5 Reasons Why Your Dirt Bike is Losing Power

For your two-wheeler to accelerate, it requires the following:

  • Fuel
  • Air
  • Spark to ignite a mixture of fuel and air

Once your bike has these three elements, nothing should prevent it from increasing its velocity from zero to maximum in a short time. If one of these elements is not supplied to your bike’s combustion chamber in the right amounts and time, the engine may not operate as smoothly as it should be. And that is why your dirt bike may not accelerate however much you try.

Below are the main reasons why your motorbike may not accelerate:

1. Plugged Jet in Your Dirt Bike Carburetor

The carburetor is the source of many problems in motorcycles and other vehicles. Sadly, many things in the carburetor prevent acceleration in motorcycles. But the good news is that each of these components is simple to fix compared to other parts of the engine.

So if your dirt bike is experiencing acceleration problems, you must take a look at plugged jets located in the carburetor. These small passageways allow fuel to flow through and mix with the air in order to make the engine run. They include pilot jets and main jets.

Sometimes these jets get clogged with dirt or tiny particles found in the fuel such as ethanol. The clogging prevents smooth delivery of fuel to the engine. As a result, the engine receives more air than fuel, leading to loss of power. With less power, your motorbike cannot accelerate.

To fix this problem, you should carefully dismantle the carburetor to examine every component inside. Then clean it to get rid of any debris that might be blocking the flow of fuel to the engine. Re-assemble it and then test the engine to see how it behaves. If the problem persists, look for a qualified mechanic to help you fix it.

2. Faulty Carburetor Springs

Even though it is small, the carburetor spring plays a critical part in the running of your motorbike’s engine. If this tiny engine component malfunctions, you will notice it within no time. The easiest way to know if it is broken is by assessing the acceleration of your motorbike.

Carburetor springs are usually located where the throttle cable comes in contact with the carburetor. Their main function is to open or close the butterfly valve or throttle valve slide during the acceleration.

Once broken, any of these springs will not open the throttle valve slide to allow air in. With a lack of enough air, your dirt bike engine will not work properly. The inability to mix air and fuel in the right proportions may cause your two-wheeler to lose power and eventually stop to accelerate.

To solve this problem, you may start by diagnosing the carburetor springs. Start by turning off your motorbike engine. Then remove all pod filters to have a clear view of the interior part of the carburetor. Examine the reaction of the butterfly valve every time you twist the throttle. Failure to see the valve movement may help you see where the real problem lies and correct it.

3. A Vacuum Leak

A vacuum leak is also a problem that causes your dirt bike to lose power that makes it accelerate. This is because the leaking allows in too much air to the air-fuel mixture, exceeding what the carburetor can handle.

Too much air and less fuel will prevent the engine from running properly. When this happens, the engine will lose power. With no engine power, your motorbike won’t accelerate.

However, you can fix this problem by examining the air intake on the carburetor. If you notice a fault on the hose clamps, tighten them to control the intake of air. If possible, replace the broken intake boot as soon as possible.

4. Poor Timing Advance

This problem is common in most of the fuel-injected dirt bikes as opposed to those with carburetors. Poor timing advance can prevent your motorbike from accelerating. The timing advance is crucial when it comes to speed.

With poor timing advance, the acceleration will not take place. This is due to the fact that the spark firing will be delayed momentarily, causing your dirt bike not to accelerate properly. At the same time, this failure will be accompanied by backfiring.

Poor timing advance is normally caused by faults in your motorbike’s electrical system. Also, it can be brought about by some faults on the mechanical timing systems.

The best way of preventing this problem is by looking for a qualified mechanic to help you solve it. Don’t do this task on your own unless you are pretty sure of what you are doing.

5. Poor Quality Gas

Bad gas or poor fuel quality can cause the engine on your dirt bike to run erratically. Sometimes fuel can become stale after a period of one month, especially ethanol mixed with gasoline. In most cases, ethanol attracts moisture for quite some time. As you may know, moisture dilutes the gas, leading to poor functioning of the dirt bike engine.

But you can prevent such cases by using high-quality fuel in your motorbike engine. Also, you should make sure that you check the expiry date of motorbike fuel before using it.

Final Thought

There are reasons why your dirt bike won’t accelerate as usual. The most common ones include faulty spark plugs, damaged carburetor springs, poor timing advance, and poor quality fuel.

Most of these problems are easy to fix but you should always take your dirt bike to a professional mechanic for better services.

Josh Berry - MotoShark Editor
Josh Berry
I'm a off-road enthusiast, extreme sport fan and the editor of MotoShark. If you have any questions or suggestions regarding this article, please leave a comment or contact me.

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