How Fast Does a 450cc Dirt Bike Go? [Answered]

How Fast Does a 450cc Dirt Bike Go? [Answered]

For a dirt bike, most riders are very particular about one thing: speed. How fast a bike will go depends on several different factors, but the first and most influential is the engine displacement. A bigger engine typically delivers more power and, therefore, more speed. But how fast does a dirt bike actually go? 

In this article, we’ll be looking specifically at dirt bikes with 450cc engines. These make up the high end of dirt bikes and are some of the fastest available. We’ll examine what makes them so quick and give a clear answer to the question of how fast a 450cc dirt bike really goes. 

How Fast Does a 450cc Dirt Bike Go?

450cc engines are found at the top of most dirt bike ranges. These are the highest displacement bikes found in motocross and typically the most powerful and fastest. While they are not usually as quick as a road-going motorcycle, they can still reach impressive top speeds. 

Most 450cc dirt bikes will top out just under 90mph when fitted with factory parts. This means that these bikes can be safely operated on public roads, provided they are equipped with the necessary components, such as brake lights and turn signals. It also means that they can reach speeds that most beginner riders may not be comfortable with at first.  

Below, we’ll dive into a more in-depth explanation of this answer to really understand what makes 450cc dirt bikes so quick. We’ll also look at a few specific examples to really see how different factors can affect the top speed of a dirt bike. 

What Exactly Does 450cc Mean in a Dirt Bike?

Most dirt bikes will include the engine size in their name. For example, the Kawasaki KX 450, Honda CRF 450, and KTM 450 SX-F are all examples of 450cc dirt bikes. In general, a larger engine will produce more power and therefore, the potential for a higher speed. 

450cc Engine

Calculating the engine displacement is done with a handy equation:

V = π/4 x (D)² x H x N

In this equation, “V” represents the volume or the ultimate cc. “D” is the bore of the cylinder, “H” is the stroke, and “N” is the number of cylinders. The KTM 450 SX-F, with a 95mm bore, 63.4mm stroke, and single cylinder has a total displacement of 449.393cc, which we round up to 450. 

What this means in practice is that the engine can produce more power! A larger bore and stroke produces a larger explosion during combustion, and that drives more force. A smaller engine, such as the ones found in 250cc and 400cc dirt bikes usually produce less power because they have smaller engines. While this isn’t always the case, exceptions are very rare.  

 Engine size also determines the class that you will race in if you’re competing in motocross racing. 450cc bikes compete within their own class, separate from the other competitors. After all, it wouldn’t be fair to have a 450cc bike competing against a field of 250cc challengers!

Also Read: How Fast Does a 250cc Dirt Bike Go?

Factors Affecting the Speed of a 450cc Dirt Bike

Besides the engine displacement, there are several other factors that determine the overall speed of a dirt bike. Some of these factors are down to the bike itself, while others have nothing to do with the design and construction of the machine. In this section, we’ll look at some of the most common factors that will affect the speed of your bike.  

Power to Weight

This is the most influential factor for a bike’s overall speed. Remember that the power of the engine must overcome the weight that it has to propel. The more weight on the bike, the more power will be required for it to move. 

Compare the wet weight of the KTM 450 SX-F and the Honda CRF450R. The KTM weighs in at around 223lbs against the Honda’s 238. Horsepower-wise, the Honda takes an advantage with just over 60 peak horsepower compared to the KTM’s 57. 

In this case, the weight is the deciding factor, as the projected top speed of the KTM is well over 100mph, and the Honda tops out at around 87 mph. Despite having more power, the Honda cannot match the top speed of its Austrian competition. 

Don’t forget, though, to factor in the weight of the rider. Even with identical bikes, two riders of differing weights will have different experiences. This is especially true if the difference in weight is significant. 

Rider Experience

This particular factor is possibly the most important to think about. Riding a dirt bike fast requires skill, and skill is only gained with experience. While one rider may be comfortable at higher speeds, another may become nervous at a certain speed, and that increases the chance of disaster. 

Dirt Bike Rider

The less experienced rider may not even be comfortable approaching the top speed of their bike, and that is a factor that will impact the maximum speed more than any specification you will find in the manual. The specifications of the bike will ultimately be irrelevant if the rider can’t handle the machine. 

Riding Surface

Dirt bikes are meant to be ridden off the road in all sorts of different conditions. Different conditions are going to behave differently, though, and that will impact the way the bike performs. Gravel and dirt, in particular, are going to slow a dirt bike down, as the loose terrain slides around under the wheels of the bike and compromises its ability to deliver the power to the ground. 

Also Read: How to Build a Dirt Bike Track

Bumpy tracks will also slow a dirt bike down considerably. Riding across bumps and irregularities in the track surface can damage the bike if going too fast and can even result in dramatic and dangerous crashes. Reaching a bike’s top speed in conditions like these is not typically a possibility. 

Dirt Bike Age

Over time, the parts and components of a bike will wear, and this results in a loss of performance. This includes parts of the engine, which determine the power of the bike, as well as chassis and suspension components that help translate that power to the ground. 

Regular maintenance can help to offset the effects of wear on the bike, but over time the parts will require more and more attention, and eventually, it will be time to replace your old bike with a newer model if you want the same performance as it once had. 

Also Read: How Fast Does a 150cc Dirt Bike Go?

Brand

While all motorcycles run on the same basic principles, competing brands will come up with new ways to maximize performance, minimize weight, and deliver a product that has some kind of edge over their competitors. 

This may come in the form of more advanced engine management or lighter materials, or even riding ergonomics. KTM’s quickshifter function, Kawasaki’s ergo-fit, and Yamaha’s power tuner app are all different features that these brands use to give them an edge.

When looking at features that specifically impact top speed, engine mapping technologies are the number one factor to look for. By allowing the rider to fine-tune the response of the engine for their preferences, manufacturers deliver bikes that can reach the top of their potential with a much wider range of riders. 

Frequently Asked Questions

What is the maximum safe speed on a 450cc dirt bike?

This will depend on the specific rider. More experienced riders will have developed skills for handling the behavior of their bike as they reach higher and higher speeds. By contrast, newer riders won’t be used to the way the bike behaves as it reaches higher speeds and, therefore, won’t be comfortable riding faster.
In the long run, your bike’s maximum safe speed will be apparent as you ride. If you ever feel like you are not in total control of the machine, that’s a sign that it’s time to slow down!

How fast does a 650cc motorcycle go?

650cc bikes come in a very wide variety of models, brands, trims, and styles. Because of this, it’s difficult to get a read on exactly how quick a 650cc motorcycle typically is. Even in situations where the engine is very similar, such as the Kawasaki Vulcan S and Ninja 650, the top speeds are dramatically different at 113 and 135mph, respectively. 
A good idea of the range of speed for this engine size would be anywhere from 95mph to over 150mph.

Is it dangerous to go fast on a 450cc motorcycle?

Any time you’re going fast, you are taking a calculated risk. The quicker you are moving, the less time you’re giving yourself to react to changing conditions, obstacles, and other riders. While riding on the road, these risks increase exponentially compared to riding on a track, as the circumstances are much less controlled, and there is more for you to account for. 
You can mitigate the danger by always wearing the proper gear, and with lots of practice, but the danger of riding fast will never be completely eliminated. Just as with the maximum safe speed of the bike, always be aware of your limits when riding, and slow down if you begin to feel uncomfortable. If you are riding on public roads, always observe the posted speed limits and follow the rules of the road. 

Conclusion

When looking for your next dirt bike, understanding the specifications is the first step in having the best experience. Key to those specifications is the engine size and the comparative increase in speed when compared to smaller bikes. The clue will usually be in the model name, such as the KX 450, FS 450, and YZ 450, all being 450cc dirt bikes. 

450cc dirt bikes are the largest bikes in motocross, and they are some of the few that can be used for transportation as well as recreation, provided they are outfitted with the proper lights and signals. Whether you’re upgrading from a smaller bike or just getting into dirt bikes for the first time, 450cc machines are an awesome way to enjoy riding offroad.

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Ryan Christian

My lifelong love of everything on wheels began with a dusty old scooter and a set of second hand wrenches. Since then I’ve spent every moment I can spare finding new dirt paths, winding country roads, and long open highways. I write to share my passion with other enthusiasts, and maybe inspire one or two new ones along the way!

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