How fast can a 450cc 4 stroke go?

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Looking for a fast dirt bike? A 450cc may be the one for you!

The average maximum speed of a 4-stroke 450cc dirt bike is around 87 miles per hour, while speed will vary based on bike modifications, the weight of the rider, engine stroke, and a few other things like terrain.

Max speed varies between different dirt bikes, so there is a lot more to learn about it.

The fastest dirt bikes are actually 450cc dirt bikes with four-stroke engines! So if you’re wanting speed, this is definitely the bike for you.

Not Designed for a High Top Speed (Like Street Bikes)

While your average motorcycle is definitely meant for smooth, paved roads, and can reach high freeway speeds, that really isn’t the purpose of a dirt bike.

Dirt Bikes aren’t really designed specifically for high speeds or maintaining high speeds over an extended period of time. Dirt bikes are essentially small motorcycles that are designed for off-roading. With a more knobby tread and good suspension, dirt bikes were created with dirt, rocks, mud, and sand in mind, rather than a paved road.

The idea is to have the best type of acceleration, control, and power to get you up hills as well as over all sorts of terrain. If all you are worried about is speed, then you might want to look into getting a street bike.

What are the factors that go into top speed?

Engine Stroke

Knowing the “stroke” of your engine will give you a lot of initial information about your bike. While two-stroke engines are generally lighter and faster, as you get up higher into the ccs (cubic centimeters) of dirt bike engines, 450cc dirt bikes with four-stroke engines are actually some of the faster dirt bikes out there. In all reality, once you get up to a 450cc engine, they actually don’t make them with a two-stroke option.

Two Stroke

Two-stroke engines are much simpler. Their operation produces less waste than a four-stroke engine does. They have a more efficient build, enabling them to be assembled using thirty to fifty percent fewer moving parts. They are the easiest of the two types of engines to clean. They do, however, have elevated fuel consumption, and because of the way the stroke of the engine works with the openings in the chamber, it produces more emissions. That being said, direct injection and catalytic converters are the exceptions to those rules.

Due to the way they’re assembled, they require fuel and oil mixture. Two-stroke engines generally require more maintenance, but the parts are cheaper. Bikes with two-stroke engines are generally lighter and faster, with more of an initial kick to the “get up and go”. While they require half the strokes to accomplish the same purpose as a four-stroke engine, some people claim that they do make twice as much noise, although others say that’s a myth, and the noise is just higher pitched, which makes it seem louder.

Four Stroke

Four stroke engines “fire” every two revolutions of the crankshaft, which delivers a steadier and more easily managed output of power. Typically a better bike for beginners, a four-stroke engine is great for trail riding and racing. There are more parts to a four-stroke engine, which means you spend less time braking and shifting your bike.

Maintenance is needed much less frequently since the work the engine is doing has been spread out through more parts. Unfortunately, this also means that when maintenance IS needed, it is generally more expensive, since more parts need to be worked on and replaced. These additional parts also make bikes with four-stroke engines heavier than their two-stroke counterparts.

High-End Bikes vs. Low-End Bikes

A general rule that unfortunately proves true claims that the more money you spend, the better the product you end up with. While many dirt bikes end up being subjected to tinkering and modification that will alter end results, when you’re talking about base models and results, the more expensive and newer models of bikes are generally faster and more efficient.

Road Conditions and Terrain

Road conditions and the type of terrain you’re riding are absolutely going to have an impact on the top speeds you’re able to reach with your bike.

Slick Roads – Water and Ice

Did you know you can actually ride your bike on ice? You can if you have the right tires. Not only does this open up new and fun terrain, but you can actually achieve a pretty decent speed while you’re at it! Get yourself a set of off-road knobble tires with studs or screws in the tires, and watch your friends faces when you absolutely smoke them in slick, wintery conditions.

Mountains – Rough, more unpredictable, speed will vary

Having your bike geared lower will enable you to ride with the most speed in the mountains. Mountain trails, typically comprised of switchbacks and lots of tight twists and turns, won’t really be the best or safest place for reaching high speeds. You’ll want tires with a knobbier tread to accommodate for the rocks, roots, and uneven trail you’ll encounter while you ride.

Weight of the Rider

In a manner similar to cars, airplanes, and parents carrying children, the more weight a vehicle is carrying, the more slowly that vehicle is going to move. Dirt bikes operate the same way. Racing techniques can help you out a little bit here for getting your bike faster.

A common consensus among racers is for every seven pounds added or subtracted, you sacrifice or gain one horsepower, respectively. Apply that to yourself, and you’ll get an average idea of what you’re gaining or sacrificing in terms of your weight.

That being said, when talking about street racing, or even normal dirt bike racing, weight generally won’t be the deciding factor unless the discrepancy between your weight and the weight of the other riders is large (and in their favor). In most scenarios, knowing how to ride and handle your bike will be much more useful to you than obsessing over weight. Riding technique is huge when it comes to racing.

If we’re talking simply about speed, racing in a straight line from Point A to Point B, the lighter guy definitely has the advantage. But if you don’t know what you’re doing, losing all the weight in the world won’t help you. If you weight thirty pounds lighter but haven’t been practicing, and you’re racing against someone who regularly practices, but just pounded a triple stack hamburger and a large shake, you’re still going to lose.

Weight of the Bike

The 450cc is one of the bigger dirt bikes, and in the world of logical thought, bigger usually means heavier, and heavier seems like it should mean sacrificing speed. That’s not quite the case for the 450cc bike though, or dirt bikes in general.

When you see “250cc”, or “450cc”, those are measurements, literally “cubic centimeters”. Describing the size of the combustion chamber in the engine, the higher the number, the more powerful the engine. The more powerful the engine, the higher the ceiling is for your speed potential.

450cc dirt bikes have the highest average speed of dirt bikes in general, if you’re going for pure speed, this is the bike for you. That being said, there is quite the number of things that you can do that will take down the weight of your dirt bike without sacrificing anything essential, aside from the money in your bank account.

When I was first trying to figure out how to make my dirt bike lighter, I was reading things about people drilling holes in parts of their bikes where they didn’t matter, desperate to get rid of any and all excess weight they could. That seems a little too much like taking a miracle diet pill to me, and in addition to that, I really don’t like the idea of drilling holes into parts of my bike where it can take it. Just because you can, doesn’t necessarily mean you should.

Let’s go over some ways you can cut down on the weight of your bike that doesn’t have the potential to compromise its structural integrity. Race day baby, let’s go!

Improving Top Speed

Ways to reduce the weight:

• Hit the bathroom – Yeah, this doesn’t really have anything to do with the weight of your bike, but it does have a lot to do with the weight on your bike. If you’re replacing nuts and bolts on your bike to save minuscule ounces, taking a trip to the bathroom before you race will make a much bigger difference than replacing those screws will. Don’t make your bike lose all the weight, do your part too.
• Like I just mentioned, you can replace nuts, bolts, screws, and the like with lighter, titanium parts. The downside, as is so common with any kind of upgrade, is the price. Coming at (hopefully) no surprise to anyone, titanium parts are a tad bit spendy, so you’re going to have to weight the cost of…well… cost to benefit and decide if that’s an upgrade you’re willing to make.
• Gas tank! – If you’re racing, do you really need a full tank of gas? Are you actually going to run out before the finish line if you don’t top off? Figure out how long the race is, figure out what kind of mileage you get on the track, and fill your bike up accordingly. Leaving out anywhere from a half gallon to a gallon of gas will take off a lot of weight from your dirt bike, so if you don’t need that full tank, don’t bring it to the track.
• The most obvious and probably common replacement or alteration people make to their dirt bikes to make them lighter is to replace the exhaust. Generally made out of aluminum or stainless steel, they add quite a bit of weight to your bike that can be lessened by replacing it with, yep, you guessed it, titanium.
  You might be thinking to yourself “isn’t titanium heavier than aluminum”? Yes, it is. If you have two exhausts built to the exact same measurements, one out of titanium, and one out of aluminum, the aluminum one will be lighter.
  Titanium exhausts are lighter because they aren’t built exactly like aluminum exhausts. Titanium is stronger, which means titanium exhausts can be built to different, lighter and thinner specifications.
• Plastics – There’s a good chance that your bike either has the plastics that it came with still on it, or you have replaced them but for aesthetic purposes. There are specific racing plastics that you can buy that are lighter, minimalist so as not to add extra weight you don’t need, but also aerodynamically shaped. Not only do they look fantastic and weigh less, but they help the shape of your bike to reduce the air resistance that occurs when you hit high speeds. Are they kind of spendy? Yep. There really is a “price” attached to success.

Change your Gearing

Gearing involves altering the bikes for a specific set of circumstances or terrain to maximize grip and tire rotation to achieve the best speed. Working specifically with the gears of the bike, you can make changes to it that will change acceleration and top speed.

If you change the gears on your bike, you’re going to be trying to change what’s called the “gearing ratio” in your favor, generally aiming for a specific outcome, and for a specific kind of terrain.

Faster Acceleration

If you want faster acceleration, you’re going to want to use a smaller front sprocket or a larger rear sprocket. Gearing your bike this way is perfect for tight trail riding, or tracks where you are making lots of turns. This creates a lower “gearing ratio”,

Higher Top Speed

If you’re looking for higher top speed, you’re going to want to change out your current setup for a larger front sprocket, or a smaller rear sprocket. You’re essentially doing the exact opposite of what you would do for faster acceleration. This higher gearing ratio is what you’d want for riding desert or sandy areas or arenas, and open areas where you aren’t making lots of tight turns.

Upgrade the Rider

Sometimes the easiest and most cost-effective way to improve your dirt biking experience is to upgrade yourself, not the bikes. If someone gave you a piano, that would be great, but unless you knew how to play it, it would be absolutely useless to you. Similarly, just because you can play the piano, don’t assume you can’t get better.

That principle applies to dirt bikes as well. You could own the newest, fastest, most expensive model of your dream dirt bike, and you may know how to accelerate and brake, but that doesn’t mean your skill set can’t improve, which would make you a better, faster driver, more effective and efficient driver.

As the old axiom says, “practice makes perfect”. Get out there and work! Look at youtube tutorials, take lessons, and if you already think you’re pretty good, ask someone you trust for tips or critiques!