How Fast Is A 125cc Dirt Bike? – Detailed Guide

What’s the Top Speed of a 125-cc Dirt Bike?

Whether you’re an absolute beginner or some rider that has some experience with dirt bikes, 125-cc dirt bikes are the perfect choice for it. Now you probably wonder what’s the maximum speed 125-cc dirt bikes can get? Well, that depends on a couple of factors such as the brand and whether the dirt bike engine is 2-stroke or 4-stroke, the type of terrain, the experience of the rider. Now some people will say that 125cc dirt bikes can’t go fast, but results have shown that their top speed opposes those talks.

The average speed of a 125cc dirt bike is 45 miles per hour. The top speed of a 2-stroke 125cc dirt bike can go up to 70 miles per hour, while the top speed of a 4-stroke 125cc dirt bike can go up to 50miles per hour.

Still, these stats are average and it’s only taken into moderation stock models from the manufacturers. There are also many other factors that can dramatically increase the top speed of a 125cc dirt bike. Putting mods to a bike to make it go faster or going downhill will also bring more speed as well. Another factor is the manufacturers themselves such as the 125cc from Honda are slightly faster than their competitors 125cc Yamaha.

Differences between a 2-stroke dirt bike or a 4-stroke dirt bike?

What’s the difference between a 2-stroke or 4-stroke dirt bike you may ask? Well here I will answer that question and by reading this part it will become very clear to you about the differences between 2-stroke and 4-stroke bikes.

The main difference between them is that 2-stroke dirt bikes are much faster than 4-strokes.2-strokes have much higher top speeds and are more suitable for track racing.

While 4-strokes dirt bikes are not all created equally. Some 4-stroke dirt bikes are faster when compared to other models. For example, the  Suzuki DRZ 125 is a 4-stroke dirt bike that can reach a top speed of around 50 miles per hour, while the Honda CRF 125 is also a 4-stroke dirt bike that can reach 55 miles per hour. This simple example shows that before choosing your dirt bike you need to research what you are really looking for in a dirt bike.

Another big difference between 2-stroke and 4-strokes is how they work as well.2-stroke dirt bikes tend to generate more rotation at a major RPM, while 4-strokes dirt bikes generate more rotation at a minor RPM.

How many seconds does it take to reach max speed?

It’s quite rare for a dirt bike to achieve top speed since it’s quite often that when you ride a dirt bike to turn a corner or you will ride on rocky roads on the trail. More important than speed on dirt bikes is acceleration, and the time it takes to get there varies on whether you’re using a 2-stroke or 4-stroke engine.

The 2-stroke dirt bikes accelerate much faster than the 4-strokes, which is why they are preferred to be used on the trail. A 125cc 2-stroke dirt bike can achieve a top speed in under 5 seconds, however, a 4-stroke dirt bike would take a little longer to reach top speed. Still, it doesn’t matter just whether the dirt bike is 2-stroke or 4-stroke, what also matters is the experience of the driver, as well as their weight.

If you put an absolute beginner on a 125cc 2-stroke dirt bike, it’s quite natural that they won’t be able to handle the power and will roll out, which means they will take longer than 5 seconds to reach top speed. Another factor that I’ll mention is the weight of the rider. If the rider is significantly heavier than the other participant, it will also take much longer to reach top speed.

Another two big factors in reaching the top speed of a 125cc dirt bike are how clean the air filters are and if your dirt bike has a wind protection system. Air filters are one of the most overlooked parts of dirt bikes, but they play a significant role in reaching the maximum speed of a 125cc dirt bike, so you must always be sure that the air filters are clean so you can reach maximum speed on your dirt bike. Here’s a guide on how to clean your dirt bike air filters.

If your 125cc dirt bike doesn’t have a wind protection system then I recommend it to you to install it. When you install a wind protection system on your 125cc dirt bike it can help you deal with the wind while riding which allows you to reach higher speeds much faster.

But the stats that I provided appear to be the norm.

Here are the stats for different dirt bike models running on 2-stroke or 4-stroke engine

Dangers of Speed

It’s not all about speed as well. As always you should know that safety comes first. Whether it’s a 125cc or even 50cc dirt bike you are not guaranteed to be free from falling once in a while. But every time you fall you should learn from it and try not to do it again.

Also, make sure you got the right protective gear when you’re on the dirt bike so even if you fall you won’t be injured as well.

Which Factors Determine the Speed of a 125-cc Dirt Bike?

There are many factors on which the rider can increase the speed of a 125cc dirt bike. There are many more but here we will take out the most important factors needed to increase the speed of a 125cc dirt bike.

  • The Engine Size
  • Modifications
  • Experience of Rider
  • Exhaust System
  • Rider Weight

The Engine Size

As we said earlier, every manufacturer makes dirt bikes with different engine sizes. This is a very important factor when it comes to the horsepower and speed of a dirt bike. 


It comes as no surprise that modifications are on this list because honestly, we all want our dirt bikes to be faster than our competitors. With modifications, we can all increase or decrease the speed of our dirt bikes.

If you wish to modify your dirt bike you’ll need two fundamental things. One is money, and the other one is experience. I will clarify these two necessities for your benefit.

You can customize your dirt bike in any way you want if you have more than enough money. All you have to do is get in touch with the dirt bike company or manufacturer, and they will do all the work for you and in the least possible time, you’ll have your dream dirt bike.

But on the other hand, if you’re really experienced to know all the parts on your dirt bike. You can get the needed parts from independent sources, which will be less expensive than getting them directly from the dirt bike company. And once you assemble all the parts you’ll have your dream dirt bike, which you will be proud of and enjoy riding. 

Here we have a list of dirt bike parts that you can change for modification.

  • Tires Whether your dirt bike is old or new, it’s always nice to change the tires. Tires with lighter weight can increase your speed compared to tires that are heavier. Also if you wish to ride in different terrain you’ll need a different kinds of tires. So changing them will also give you experience in changing the tires and help you ride in different terrains.


  • Stock Sprocket If you want to achieve high speed while at the same time maintaining your low-end torque acceleration, then you need to change the stock sprockets.

But before you change the stock sprocket on your dirt bike you should be aware of the ratio of it. For every 1 tooth you change in the front it is the same as changing 3-4 teeth in the rear which will result in faster acceleration.

If you want to achieve higher speed then you need to use a larger front sprocket or the smaller rear sprocket.


  • Aftermarket Exhaust  

One of the most popular and famous modifications on dirt bikes is the exhaust. An aftermarket exhaust can give an extra boost to your dirt bike engine and with that, you will be comfortable covering more distance with your dirt bike.


  •  Suspension If you love to ride on rocky terrain then you will need a new suspension system that will bring more comfort to you and at the same time suspension can protect you from danger as well. So it should not be looked at suspensions as expenses but rather as an investment into your dirt bike.

Experience of rider

Another big factor in increasing the speed of a 125cc dirt bike is the rider experience with riding dirt bikes.If a beginner sits today on a dirt bike he won’t have the freedom in himself to increase the speed of a dirt bike, because he will have some fear. While a pro rider will increase the speed without a problem since the more you ride freer and better you become. 

But if you’re a beginner don’t get discouraged by what I just said. All you need to do is ride more and with time and practice, you too can increase the speed or do some tricks.

Still, if you feel uncomfortable or unsafe while driving at top speed, you should lower the speed, because after all safety comes first.

Exhaust system

Exhaust systems are very powerful if you want to achieve top speed. There are two kinds of exhaust systems. One is 2-stroke other is a 4-stroke exhaust system. 2-strokes are better when it comes to increasing speed because they are lighter, cheaper and you can increase the speed. While 4-stroke exhaust systems are heavier and much more expensive and you won’t be able to increase the speed as much as with a 2-stroke exhaust system.

Also, another factor in the exhaust system is the material they are made of. Most exhaust systems today are made of either aluminum or steel, but there are some exhaust systems made of titanium. Titanium exhaust systems are lighter than the ones from steel or aluminum which equals higher speed as well.

Rider Weight

If you want to ride for fun and enjoyment then the weight doesn’t play a role. But if you’re a rider who wants one day to go on to race tracks then the weight plays a very big role.

RIders with a lot of weight will have lower speed and performance than riders with lighter weights. It won’t matter if the riders have the latest dirt bike model or all the skills and experience at the end of the day their weight will still determine their dirt bike speed.


Riding a dirt bike is very funny and enjoyable. Some riders do it for fun while others ride as professionals so that they can compete in the race tracks.

Since all rides want fast bikes, we came to conclude how fast a 125cc dirt bike is. Well, the answer to that question is it depends. It depends on many factors such as the type of brand, the riding technique, rider experience, and weight, and many others.

Still most 125cc go around 45 miles per hour, on extreme ends it can go up to 55 miles per hour. You can also modify your dirt bike to make it faster up to 100+ miles per hour as well.


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