Dirt bikes are versatile and impressive machines that have evolved over the years, and now display the pinnacle of human engineering in the two-wheeled motor world. However, whether you own one yourself or plan to get one, you might wonder which are the fastest dirt bikes in the world.
The 5 fastest dirt bikes in the world are:
- KTM 450 SX-F (123 mph)
- Suzuki DR-Z (114 mph)
- Aprilia RXV 5.5 (113 mph)
- Husqvarna TX (112 mph)
- Honda XR (110 mph)
It’s worth noting that top speed clearly isn’t everything when it comes to dirt bikes, and it’s often hard to find accurate top speeds for the bikes out there because most people don’t push them to this limit. However, we will take a closer look at each of these bikes below.
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The 5 Fastest Dirt Bikes In The World
1. KTM 450 SX-F (123 mph)
The KTM 450 SX-F is an upgraded version of the 450 SX that was similarly breaking records for a long time before the entry of the 450 SX-F. Its 449cc engine propels the relatively light bike to a top speed of up to 123 mph (198 kph) with the right gearing, making it the fastest conventional dirt bike on the dirt bike scene.
2. Suzuki DR-Z (114 mph)
The Suzuki DR-Z 400SM was built for paved pathways and tarmac racetracks, but if you are willing to buy a new set of dirt bike tires for it, the DR-Z 400SM gains considerable offroad capabilities. It has an engine size of 400cc and goes on to reach up to 114 mph (183 kph). It has a surprisingly light body frame with a slim chassis, making for a smooth and nimble riding experience.
3. Aprilia RXV 5.5 (113 mph)
The Aprilia RXV 5.5 weighs 303 pounds, and it utilizes a 549cc engine to deliver 55 horsepower and a top speed of 113 mph (182 kph). In terms of acceleration, the Aprilia is an extremely fast bike, taking just over 4 seconds to get from 0 to 60 miles per hour.
4. Husqvarna TX (112 mph)
With a top speed of 112 mph (180 kph), the Husqvarna makes use of its 300cc engine to full capacity. The TX300 has a relatively small engine as compared to all other dirt bikes on our list, and the power it produces is largely because of modern engineering that increases the efficiency of the dirt bike, and its fairly light weight.
5. Honda XR (110 mph)
Honda has been producing dirt bikes for several decades, and it is therefore not a surprise that they have the right technical knowledge to produce some very quick bikes. A powerful dirt bike that offers 40 horsepower through its massive 650cc engine. It’s capable of a top speed of 110 mph (177 kph).
Torque vs Power In Dirt Bikes
Power and speed are two different aspects of a dirt bike. Power can be loosely described as how fast the engine can perform work.It is different in both torque and speed, but they are all interconnected. Torque is the twisting force that propels your dirt bike forward. Speed on the other hand, simply put, is how fast you can cover a given distance.
Different dirt bikes have different levels of performance when it comes to each of these specifications, and it is therefore difficult to find one that excels in all of them. For example, you can have a very powerful dirt bike with a lower top speed than a bike with less power. Things like torque and weight come into play too.
Torque and power are common specifications associated with vehicles and their engine capabilities, and this remains true for dirt bikes. Torque and power are what get your dirt bike moving. Different amounts of torque and power produce different results, and therefore when choosing a dirt bike, it is important to consider both individually and also as a pair.
What Is Torque?
According to mechanical physics, torque is described as a force that causes rotation. In simple terms, torque is a measure of the ability of the engine to turn the crankshaft. There are many definitions of torque, but this is the most relevant to dirt bikes. It is usually measured in Newton meters (Nm) or foot-pounds (ft-lb).
A dirt bike with a torque of a 100 ft-lbs can turn the wheel by its axis on the crankshaft with a force of a 100 lbs for a wheel diameter of one foot. The higher the torque value, the easier the bike’s engine can convert its power into motion in the crankshaft and therefore rotation of the bike’s rear wheel.
What Is Power In Relation To Dirt Bikes?
Power generated by the dirt bike is usually measured in terms of horsepower. Power refers to the rate at which something can perform work. A powerful bike takes a shorter time to reach its top speed than the exact same bike with less power. It can also be said that increasing the power generated by the engine often increases your top speed.
Which Is Better, Power Or Torque?
Both power and torque are beneficial to a dirt bike’s performance. When choosing which is more important, it all boils down to your riding style. How you are going to ride your dirt bike and the conditions you intend to subject it to will determine how much torque or power you need from your engine, and how much of the two you can afford to compromise.
If you have the need for speed and would like to experience higher top speeds, then going for a powerful dirt bike is more important than one with plenty of torque (although it’ll usually have a lot of that too anyway). If you are looking for a dirt bike with the ability to pick up quickly and accelerate quicker, then the more important metric to consider is how much torque it offers.
In normal circumstances, however, an ideal bike should blend both power and torque to produce a dirt bike that can accelerate quickly and hit decent top speeds. But again, other things are worth considering too, such as the bike’s weight, how easy it is to handle, the overall size of it and the brand or model. But if power and speed are your goal, what else should you consider?
What Affects The Power & Speed Of A Dirt Bike?
Engine Capacity
The displacement of your engine determines how well it is able to generate power and torque. Usually, a bigger engine translates to more power and torque. Bigger engines have the capacity to fit in more cylinders, which can greatly increase the amount of horsepower generated. Even with a single cylinder, the volume of space available for internal combustion greatly influences power output.
The Quality Of Gas
For dirt bike owners looking for maximum efficiency in torque and power production, premium high-octane fuel is a worthwhile investment. Using stale or poor-quality fuel in your dirt bike might cause it to behave in an erratic manner, which greatly reduces the power output and torque production. It is better to go the extra mile to obtain high-quality fuel if you can afford it.
Weight And Build Of The Rider
The weight and build of the rider are essential in determining the riding experience and the top speed reached by the dirt bike. Different dirt bikes are designed for different weight ranges, and overloading your dirt bike prevents you from reaching top speeds by straining the dirt bike’s engine.
Too much weight on the dirt bike can also cause handling problems which reduces agility when handling tight bends or sharp inclines.
2-Stroke vs 4-Stroke Dirt Bike Engines
Ever since the internal combustion engine was invented, and the patents for both two-stroke and four-stroke engines were given, a heated debate erupted. The debate has persisted for decades despite the current advancements in technology and testing procedures.
Before diving into the different advantages of each of these dirt bike engine types, it is necessary that you understand how each engine works. The difference between the two engines stems from the number of strokes required to complete a combustion cycle.
How Does A Four Stroke Engine Work?
In a four-stroke engine, just like the name suggests, the engine requires four strokes of the piston (upward and downward movement of the piston in the cylinder) to complete a combustion cycle. The four strokes translate to two crankshaft cycles.
The different strokes correspond to the intake of the mixture of fuel and gas, the compression of the mixture, the combustion phase, and finally the expulsion of the exhaust gases.
The initial downward movement of the piston, or the first stroke, creates a region of reduced pressure in the combustion chamber. Greater atmospheric pressure causes an inflow of a mixture of fuel and gas into the cylinder. The second stroke of the piston reduces the volume occupied by the mixture of fuel and gas, which causes a compression of the mixture.
The next stroke that initiates the second crankshaft revolution is the ignition of a spark in the combustion chamber. The spark generated ignites the mixture of fuel and gas causing internal combustion. The sudden explosion of power pushes the piston downwards. The final stroke in the cycle pushes the expended gases through the exhaust system to allow a fresh mixture to enter the chamber.
How Does A Two Stroke Engine Work?
A two-stroke engine cuts down on the number of strokes required to complete a cycle by incorporating the process of compression and ignition into one stroke and the second stroke takes care of the expulsion of exhaust gases and drawing in of more fuel and air. This is achieved through a mechanism that involves clever positioning of the valves opening into the combustion chamber.
Which Is Better: A Two-Stroke Or A Four Stroke Engine?
When choosing which dirt bike engine to use, understanding your personal expectations is key. It has been widely accepted that both two-stroke and four-stroke dirt bikes are worthy choices for riders. The fact that both of these dirt bike engines have been used by world-leading racers in different dirt bike competitions only adds to fuel the debate.
The two-stroke dirt bike engine is an excellent option for people looking for a faster accelerating dirt bike. The four-stroke dirt bike produces a steady speed and torque, even if it might not accelerate quite as fast. In the long run, it offers a smoother ride, is quieter, and produces fewer harmful exhaust gases as compared to the two-stroke engine.
Final Thoughts
Top speed might not be a term commonly associated with dirt bikes, but there are several dirt bikes that can go incredibly fast at their limit. It is an engineering marvel that two-wheeled vehicles with small engines can produce enormous amounts of speed and power, and the KTM 450 SX-F is the fastest among them.