How Fast Can A 125cc Dirt Bike Go: Find Out Its Maximum Speed!

The popularity of dirt bikes dates back to the 1960s. Since then, more and more riders have embraced dirt biking as a sport. Today, teens have gone crazy about dirt bikes, and the 125cc model has impressed most of them. It is an upgrade of the 100cc and 50cc bikes, which means better performance and faster speeds.

But, how fast can a 125cc dirt bike go?

Dirt bikes with 125cc engines can reach a top speed of between 45mph and 60mph. However, it depends on other factors like engine type, weight, terrain, brand, etc. For example, while most 125cc dirt bikes with a 4-stroke engine can attain a high speed of 45mph, their 2-stroke counterparts can reach 60mph, some even 70mph.

Different dirt bike riders have different insights and ideas on the maximum average speed of a 125cc dirt bike. If you’re in a gray area, take time and read through this article to find out more about 125cc dirt bikes.

What Age Is a 125cc Dirt Bike for?

Getting the right size dirt bike for your kid is essential for their riding experience. It makes the activity more enjoyable and safer. A kid’s dirt bike should match their height, age, and confidence to the engine capacity and seat height.

We have discussed dirt bike size chart before; here is an overview of kid’s age versus bike engine size:

Kid’s Age	Engine Size (cc)	Kid’s Height	Seat Height
3 – 7 years	50cc	2.7ft to 3.7ft	17” to 21”
7 – 12 years	50cc, 100cc, 110cc	3.7ft to 4.7ft	21” to 25”
12 – 14 years	125cc	5ft to 5.2ft	31” to 35”
14 – 17 years	125cc to 250c	5.2ft to 5.8ft	35” to 38”

Kids grow really fast, and they outgrow their bikes sooner than expected. The temptation to buy a bigger dirt bike so they “grow with/into the bike” can be overpowering to most parents. It’s a good strategy when buying new clothes but not for dirt bikes. Buy the right size bike for your kid; a 125cc bike is an ideal dirt bike for a 13 year old.

How Fast Can A 125cc Dirt Bike Go?

In the dirt biking world, power and speed matter to most riders. As they progress and improve their skills, they get the urge for more power and speed. As aforementioned, a 125cc dirt bike can hit a maximum speed of 60mph.

Different engine types, the bike’s weight, terrain, and rider experience, will produce different results. Most importantly, as a rider, ensure you ride your dirt bike at a safe and comfortable speed.

2-Stroke Engines Vs. 4-Stroke Engines

One of the most crucial considerations when buying a dirt bike is the engine type. It has a direct impact on the bike’s overall speed and performance. Regardless of your engine capacity (CC), there are two engine types across all dirt bikes; 2-strokes and 4-strokes.

The primary difference between a 2-stroke and a 4-stroke engine is the number of stages they undergo to complete a power stroke. A 2-stroke engine goes through two stages, while a 4-stroke goes through four stages. For this reason, a 2-stroke engine produces two times more power than a 4-stroke engine.

A 2-stroke engine is more powerful and lighter. It combines the upstroke ignition and compression steps with the downstroke power and exhaust steps. This method is easier to maintain since it utilizes fewer moving parts. However, it provides less torque. A 2-stroke engine operates in two stages as follows:

• Upstroke – It involves ignition and compression. The piston travels up, allowing air and fuel into the crankcase. The mixture is then compressed and ignited.
• Downstroke – It involves power and exhaust. After ignition, power is produced, and the piston is pushed downwards to expel the exhaust.

A 4-stroke engine is heavier yet less powerful. However, it’s eco-friendly and fuel-efficient. A 4-stroke engine operates in four steps as follows:

1. Intake – The valves open, and a downstroke occurs to draw in fuel.
2. Compression – Fuel is then compressed by an upward movement of the piston.
3. Power – Once the fuel is compressed, it’s ignited to produce power.
4. Exhaust – The exhaust valve opens to expel exhaust gas (Carbon monoxide).

Keep in mind that both engine types have their strengths and drawbacks, including prices; pick one that suits your riding needs.

Factors that Determine the Speed of a 125cc Dirt Bike

Regardless of the machine they power, every engine has a manufacturer’s defined speed limit. A 125cc dirt bike has a maximum top speed of 60 miles an hour. However, other underlying factors can significantly affect its speed.

Below is a comprehensive description of factors that determine the speed of a 125cc dirt bike:

Sprocket Gearing

The gear ratio is essential for speed on a 125cc engine. A larger front drive sprocket combined with a smaller rear sprocket produces more wheel RPM (rotation per minute) hence faster speed.

Engine Size

Dirt bikes come in various engine types and sizes; it is significant when it comes to the performance and speed of your bike. A 125cc dirt bike with a 2-stroke engine will certainly ride faster than a similar bike with a 4-stroke engine.

Rider Experience

A novice rider may not ride fast on a 125cc dirt bike due to fear and lack of confidence. An experienced rider, on the other hand, with confidence and experience, can handle a dirt bike at high speeds and even perform some stunts.

Don’t push your bike to the limit if you are a beginner rider; remember safety first. Try to build confidence and experience first before attempting top speeds.

Modifications

Most dirt bike riders want their bikes to be faster than competitors, thus modifying them. If done correctly, modified bikes ride faster than they were initially built. Some modifications include tires, aftermarket exhausts, sprockets, etc.

Weight

Weight is not a crucial consideration for riders who ride for adventure and fun; however, it is critical if you intend to do dirt bike racing. The more the bike’s weight, the slower the speed. It doesn’t really matter if you have the latest model in the market or expert skills.

This factor is more prominent in 250cc dirt bikes as those are for more experienced riders, and they want lighter and faster rides.

Tips and Tricks to Make Your 125cc Dirt Bike Faster

125cc dirt bikes are fast. And these are some tips and tricks to make your 125cc dirt bike go even faster:

• Adjust your suspension – Buying an aftermarket 125cc dirt bike suspension might be a costly mod, but worth it after all. With an improved suspension, you get more comfort and better control of your bike regardless of the terrain. This positively affects your dirt bike speed.
• Remove carbon residue – More often, carbon residue accumulates inside your bike’s exhaust pipe, blocking airflow into the engine. This affects the performance of your bike. Disassemble the exhaust and muffler, and use a rag or brush to remove the buildup of carbon residue. You can also modify it by drilling holes to boost airflow into the engine.
• Boost compression – Changing the compression ratio of your dirt bike helps enhance its performance and increase speed. This process varies depending on the engine type. Changing a 2-stroke engine’s compression ratio involves milling the head. On the other hand, for a 4-stroke engine, you’ll have to replace its pistons with dome-shaped pistons.
• Open the valves – The engine’s balance of fuel and airflow is significant for your dirt bike’s speed and performance. If you increase the air flowing to the engine, you boost its power. A camshaft is used to regulate the airflow by closing and opening valves.

A high-performance camshaft allows more air by letting the valves stay open for long. It’s recommended to hire a professional to help you with this job. They can easily determine which camshaft suits your engine setup and riding style.

How Long Does It Take To Reach Top Speeds in Dirt Bike?

Due to the nature of dirt riding sport/racing, it’s rare for these bikes to attain and maintain their top speed. Acceleration is more important than speed. The question of how long it takes for a 125cc dirt bike to reach its top speed entirely depends on the type of engine.

A 2-stroke engine accelerates faster than a 4-stroke engine resulting in an efficient acceleration. A 125cc dirt bike with a 2-stroke engine can achieve its top speed within 5 to 10 seconds, while its 4-stroke counterpart would take longer than 10 seconds. Also, what matters is the weight and the experience of the rider.

Final Words

Dirt bike riding is an adventurous and enjoyable activity. Some riders do it professionally for races, while others do it for fun which it is, for sure. Since most riders love speed and 125cc dirt bikes are the most widely used, we came to analyze how fast these bikes go and how to improve their speeds.

125cc dirt bikes are not designed to race like beasts; however, some modifications can be done to make them go faster. We hope you find the tips above helpful in transforming your dirt bike into a speed monster. Above all, SAFETY should be the biggest priority, and be sure not to damage your bike.