How Fast Does a 125cc Dirt Bike Go?

Most people love riding on a bike either simple one or classy. For terrain areas, dirt bikes are the best ride for lovers and rigorously we always seek how fast does a 125cc dirt bike go. Some bikes run chaotic, some are just cool. From childhood, most native boys love a dirt bike in terrain areas of America, Mexico, Equator, Peru, and Chile. Because of the geographical privileges over there, lots of terrain and hilly regions are available for dirt bike racing. Motocross riders favor these places for their practice, racing, hiking, and challenges. In this short article, we’ll discuss 125cc dirt bike’s speed, enhancing tips, boosting tricks, and many more. Stick to it and take yourself to the biker world. You can check also – How to Clean a Dirt Bike Air Filter?

How Fast Does a 125cc Dirt Bike Go?

Factors of a 125cc Dirt Bike Speed

Everyone loves speed whether they’re in practical life or in computer games. Even you might love speedy bike racing games on android devices. Telling you a secret, I occasionally play android racing games of dirt bike online and take challenges from diverse players. To become the top racer, speed knows no grievance. Recently most computer or android games are made of real-time or practical life experiences. In this joint, experiencing in real life and in a game are coordinated precisely. Major factors of a 125cc dirt bike speed are- engine size, gears, modifications, physics, and weight. Let’s discuss in a nutshell. Related – How to Wash a Dirt Bike?

Engine Size

Apparently, it is fixed for a 125cc dirt bike. However, it is recommended to use a dirt bike from 70cc – 150cc at 12-18y of age. The elder you grow, the more engine size you can enhance. Expert riders use 250cc dirt bikes even. Furthermore, a 125cc dirt bike speed starts from 70-110mph. Mostly engine size means engine capacity. Hence a 125cc dirt bike means the capacity of this bike is 125cc (fuel capacity).


For a dirt bike, we’ve found two categories- 2 stroke and 4 stroke bikes. Mostly these are known as gears however people often forget about throttles. A 2 stroke 125cc has enough speed than 4 stroke ones. Because of lightweight, speed boosted up in a 2 stroke dirt bike. Basically, it starts from 70mph in a 2 stroke 125cc dirt bike where the 4 stroke 125cc dirt bike top speed is 50mph.


Modifications depend on bike boosters. Clutches or brakes are lighter and boost speed up. A good engine oil enhances speed also. Nitro boosters can be both internal and external. External nitro boosters are excellent for gearing speed up. Another boosting performer is a gear tooth. Usually, external nitro boosters enhance speed 10-25 times than normal. For example, if you have a 125cc 2 stroke bike, the normal speed is 70mph. But with an external booster, you’ll get around 100mph speed. Likewise, for a 4 stroke dirt bike, general speed is 50mph that boosted up to 80mph using external boosters. Besides, internal boosters are random for diverse manufacturers. Some companies provide internal boosters that boost speed up to +10mph maximum.

Physics of Speed

Obviously a 125cc dirt bike needs some dynamics and mechanics. Scientifically we know the speed as the ratio of distance to time. But in a dirt bike, a simple ratio of distance and time doesn’t work that much. Bike manufacturers work on speed and they figured out some common physics of dynamics. A 125cc dirt bike turns into a speedy one if we maintain gyroscopic effects, a center of mass, suspension, and torque. Torques can be eliminated from the list because it depends on motors of the engine. Center of mass is essential for speed calculation and friction. Enough of friction cause hindering of the engine. Better wheels can reduce friction. Suspension is like nitro boosters and used as an internal booster mostly. Some manufacturers produce bikes including suspension or excluding, however you can use an external one always. Center of the mass of a bike should be aligned and capacitive. It controls the bike’s handling and movement.

Weight and Geometry

In a word, you should purchase a lightweight dirt bike with durability. The excessive weight of a 125cc dirt bike reduces speed. For example, if your bike weighs 147 lbs and you weigh 100 lbs, in total the weight is now 247lbs. Contrarily, another biker weighs 110lbs with 125lbs bike, a total of 235lbs. So the speed varies much for this mere 12lbs difference. Mathematically it is proven that this 12lbs difference causes a 10% variation of speed. Geometry of a 125cc dirt bike is also necessary because of weight measurement. The more complex design, the more speed reduction due to weight increasing.


Related: Best 4 Stroke Dirt Bike for Trail Riding


How Long It Takes to Reach Top Speed

There are lots of speedsters in dirt bike racing. In the beginning, speed increases slowly and in the middle, it boosts up. As time runs, speed increases gradually. If the tracks are smooth, slippery and no major bulks there, a 2 stroke 125cc dirt bike speeds up to 80mph without nitro boosters. However, a 4 stroke bike gets 56-78mph maximum with nitro boosters. Delay time reduces up to 2 seconds for an advanced technology bike. With a duration of 2 seconds, speed enhances to 10% each slot. Say, you start with 30mph and boost the gear. So a 2 stroke 125cc dirt bike will speed up to 50mph in half a minute; top speed within a minute accordingly.

Similarly, a 4 stroke 125cc dirt bike will gear up within 2 seconds by 10%. But there’s a problem in a 4 stroke 125cc dirt bike. During speed up, it skids sometimes even you’re an expert rider. A 4 stroke engine has 4 slots of Sprocket and it gears up sequentially but takes little time like 2-3 seconds. Moreover, if you want to gear up faster, it would slip or crash.

Related: Best Starter Dirt Bike Review & Guide

Dangers and Preventions

125cc dirt bikes speed-enhancing has some privileges as well as demerits. Not only dirt bikes but also every bike has this danger. Anyways, lots of preventive steps and precautions are available from expert’s solution. From their aspects, we figured out the most common dangers of boosting the speed of a 125cc dirt bike.


  • Due to overspeeding, 90% of the chance to skid always. If the roadways are sloppy and muddy, it would cause severe injuries. Scratches, dislocations of bones, cracks in knees are familiar to dirt bike racers. It is rare to find a dirt biker who didn’t experience any accident whether minor or major.
  • Nitro boosters are occasionally dangerous because it enhances speed faster and drastically. Even brakes don’t work well during nitro. Hard braking during a nitro boost cause firing in conveyor belts or chains. This causes serious mishaps. Internal nitro boosters are precisely good to use for newbie kids.
  • Brakes are an important element of a 125cc dirt bike. Brakes and clutches are placed parallelly in the handle. Clutch motivates direction and angle where the brake is for stopping at once. If these both are pressed at a time, the bike will lift up or jump forward/backward. Without proper practices and trials, people shouldn’t do this in-field. Some manufacturers prepare clutch as a mini speed booster so check the manual before purchasing a dirt bike.
  • Engine motors are sensitive, warm, stay closer to biker’s leg, and pretty noisy. Air filters of a dirt bike reduce some noise but not totally. When you in a race tournament, lots of mental pressure suppress on you, and tension increases gradually. Due to this tension, people can’t follow common instructions even. A slight touch of a running bike’s chain on to your toes causes a dangerous situation.
  • Mostly, 125cc dirt bikes are used for older kids. They feel flexibility and lots of fun factor riding it. However, it is not recommended for elder people who already experienced much. Elder bikers grip dirt bike handle firmly and adjust angular options amicable. This matter causes bothering kids and they may feel uneasy.


We suggest preventives from skid, crash, healths of both bike and rider, human-bike coordination, and accidents on swampy highways. In most cases, dirt bikes have fame to drive on hilly arenas, dirt roadways, trails, terrains, and hiking. Junior school boys love to ride and jump along with. Despite all disadvantages, some preventives can assist the longevity and durability of a rider and the bike as well.

  • Use knee pads during a bike ride. Lots of foamy knee pads are available in marketplaces and specifically built for riders. Collect accurate sizes and wear on both knees.
  • Dirt shoes are mandatory. It prevents from skid and rough pathways. Also, it prevents sudden slip on moisture roads. But keep concerned about quality products. Numerous duplicate products are available that last few days only.
  • Hand gloves are essential as well. Although super comfy grips cover the handlebars of a dirt bike, it is compulsory to wear hand gloves. Without hand gloves, some tournament doesn’t allow bikers even.
  • Check gasoline or fuel of the dirt bike before riding. If the indicator not working properly, change the indicator. Without full-tank fuel, speed shrinks down faster in a blink. Don’t use nitro boosts when the fuel indicator is low. Besides, it is not recommended to use nitro boosts successively. Use those with some duration.
  • Flexibility of the handle neck is a must. If you feel the bike neck doesn’t work well or stuck in, use some lubricating oil on the bolt joints. Grease or normal glycerin can do in dying moments.
  • Riders experience and level is the last concern. 125cc dirt bike can raise speed up to the top unless the rider is an expert in biking. Don’t involve in any championship if you are a newbie rider.


Related: Best Dirt Bike for 9 Year Old Kids


Speed Vs Control for a 125cc Dirt Bike

Yes, controlling a 125cc dirt bike is the key concern first. Without acute controls, you shouldn’t ride one. In racing championship or motocross madness, severe controlling is required much. The bending, edge, and angle are important. Red Bull racing trials always use lots of different angles and fringes. Riders have to pass the brake-n-go method while facing serious corners like 90 degrees to higher. Narrow paths to pass with terrain obstacles keep a rider busy all the time. Experience and expertise are too much mandatory for racing. When any sharp edge comes, a rider must have to stuck for seconds then go again. This is well-furnished by better control. Speed comes to null from the top with clutches and brakes.

Speed and control are somewhat inversely proportional to each other. Any of these increases, the other decreases gradually. Just imagine for a simple moto GP bike or Honda bikes- when you ride with the maximum speed on a straight road, definitely, you need no controlling unless any obstacles arise. Contrarily, when any obstacles come along the path, controlling is essential than speed. Rough edges, rims are the most available stuff in dirt bike racing. For a 125cc dirt bike- either 2 stroke or 4 stroke- each bike can provide the top speed as 70mph. For a 2 stroke dirt bike, controlling is superb and easy but less durable. For a 4 stroke dirt bike, controlling is hard and takes seconds somehow, but these are accurate for speed and features. Anyways, if you wanna be a speedster, you have to learn every style and action of bike control. However, if you wanna be a moderate rider, relevant features of controlling should be aware of then speed.


Related: Do You Need a License to Ride a Dirt Bike

Top Speed of a 125cc Dirt Bike

Honestly speaking, a 125cc dirt bike is famous for kids and teenagers. Specifically, in some hilly region or terrain areas, downtowns, villages- dirt bike is necessary for the fun factor, daily usage, time passing, and to go anywhere. Mostly in America and Chile, lots of terrain areas and mountains there. In rainy season/monsoon, these areas become rough, muddy, landslides increase drastically, and tiny rocks everywhere. So it is hard to ride normal bikes or racing bikes there. Dirt bike wheels are perfect for these areas as well as the control. However, we are discussing the speed of a 125cc dirt bike in this article, so let’s get to the point.

First of all, you have to decide why you need a dirt bike. Probably it supports you in daily tasks or you wanna be a racing pro. For regular usage, you need no speedy ones rather need 4 stroke dirt bikes for enough durability. For a racing pro, you have to pick the 2 stroke dirt bikes because it enables quicker speed. Furthermore, you should aware of some common things here-

  • A 125cc dirt bike speeds up to the top 70mph within 4 seconds, mostly.
  • The most fabulous feature of a 125cc dirt bike is its flexibility. Kids are strongly recommended to have it once in a lifetime. It goes everywhere at the speed range of 35-75mph. Sometimes it speeds up more than the featured.
  • Manufacturers tell in the specifications about speed however every dirt bike gain more speed than the documented speed range. Basically, this one depends on user mobility and caring.
  • For obstacle riding, faster bikes aren’t that useful. Rather you need 4 stroke dirt bikes instead. The handling and braking are better in a 4 stroke dirt bike.
  • As we said earlier, faster bikes or speedy ones need more control because of decreasing controls. To fulfill the reduced control in a speedy bike, expertise must be grown-up for a rider.

Lots of factors and credentials are available for a 125cc dirt bike. The more you ride, the more you gain knowledge about it.


So far it is clear that a 125cc dirt bike top speed varies within 35 – 80 mph and occasionally higher. We recommend a 125cc dirt bike for 12 – 12+ kids with a height of 5 – 6 feet. Moreover, the seat height should be 30 – 40 inches from the ground. Wheels are important also because it supports the gravity on rough roadways. So we recommend the best tires from manufacturers. However, you can change good quality wheels when required. Smooth-shifting is another minor factor of top speed though it is tough to create one. Finally, maintenance and troubleshooting is the last step to recommend. Use proper filter oil, lubricants for a 125cc dirt bike.


It is easy to speed up on any ride but difficult to control smoothly. Expertise and experience of a rider can do anything in any critical situation. During dirt bike racing on rough motocross, you need less speed than controls. But on a smooth flexible downtown roads, definitely, you gear up to the top speed. If any further queries, feel free to ask us. Please share our tutorials, articles, suggestions if you think this useful.