KX100 Top Speed: Fast Enough, or Too Fast?

Everyone who owns a dirt bike wants to know how fast it goes – including you (and me). In this post, we’ll look at the top speed of a KX100.

Whether you’re a young racer wondering how fast your KX100 is that your parents bought you, or if you are the parent who is purchasing this bike for your kid and you’re wondering what the top speed of a KX100 is, we will be covering that here in this article, as well as what impacts it.

KX100 Top Speed

Kawasaki has long been one of the dominate players in the dirt bike world, especially in the youth motocross bike world, with bikes such as the KX100 and KX65.

What does this mean for the KX100 top speed?

The KX100 top speed is about 65 mph.

This is about 10-15 mph faster than the KX65 top speed. It’s also about 5 mph faster than the YZ85 top speed.

Why did I pick these two bikes to compare the KX100?

First, the KX65 was picked because 100cc dirt bikes are a natural progression for kids moving on from a 65cc dirt bike. Often they’ll move from a 65cc bike to an 85cc, but sometimes they skip the 85s or get both the 85 and the 100 at the same time.

The YZ85 was chosen because of what I just mentioned. As kids progress, they go from 65s to 85s to 100s, if not riding some combination of them all at the same time. 100s are often seen as a good stepping stone between 85s and 125s.

It made sense to then compare all three of these bikes here in this one article.

What changes the top speed of a KX100?

It can be tough to calculate the true top speed of a dirt bike because there are quite a few different items that can impact it. Let’s take a look at them.

Engine Work and Aftermarket Parts

This might be obvious to some, but engine work and aftermarket parts are going to impact the KX100 top speed. Arguably, most of anything.

If your KX100 has engine work (especially a big bore kit) and a pipe, that’s not really comparable to the top speed of a stock KX100.

The speed of a KX100 that hasn’t had any work done to it will be significantly lower than the top speed of a KX100 that has undergone a lot of mods.

The more work you do to the bike, the greater the difference in speeds will be. You spent a bunch of money on the aftermarket parts to make it faster, didn’t you?

There are other factors at play here too – such as gearing, riding conditions, and more.

Gearing

The second most important factor in determining the KX100 top speed is its gearing. Gearing refers to the size (and ratio) of the front and rear sprockets.

For reference, the stock gearing for this bike is a 13-tooth front sprocket and a 51-tooth rear sprocket (depending on the year of your bike).

Riders, or in this case their dads, normally pick different gearing depending on the situation they’re riding. If the rider is racing a tight, technical track, they would typically want more acceleration (also referred to as more bottom end). To achieve this, they’d use either a smaller front sprocket or a larger rear one. This is known as having a low gear ratio.

If the rider is racing a motocross-style track, they may want more top speed (known as top end). To do this, the rider would use a larger front sprocket or a smaller rear sprocket; in other words, they would be changing to a higher gear ratio.

Riding in the woods can require an entirely different gearing combination than both of those.

This might not sound like much to some people, but it has a large impact on the top speed of any dirt bike, including the KX100. It not only impacts how fast the bike can go, but also where the bike makes its power.

A KX100 with a 6-tooth front sprocket will have a different top speed and make power differently than one with the stock 14-tooth front sprocket (I made the difference wide to make a point — no one is running a 6-tooth front sprocket on their KX100….).

Additionally, a change to the front sprocket has a greater effect on a dirt bike than changing the rear sprocket. Going up or down one tooth on the front sprocket is not equal to one tooth on the rear sprocket.

Rather, changing the front sprocket by one tooth is equivalent to 3-4 teeth in the rear.

Rider: Size and Ability

The top speed of a KX100 is going to be slower if the rider weighs more because it takes more work from the bike, while the bike and engine maintain the same ability/capacity. The heavier the rider, generally the lower the KX100 top speed is going to be.

In addition, an experienced rider can make the KX100 go faster than a beginner who is just learning. A rider who knows how to quickly and smoothly shift gears can hit a higher top speed than someone who is just learning how to use a clutch.

Consider Haiden Deegan on this size bike (not long ago) versus a kid who got this as their first dirt bike and is just learning.

Conditions of Riding

The KX100 top speed can also be impacted by riding conditions, including both location and surface.

For example, a dirt bike’s power output is generally higher closer to sea level than at high altitudes. So if you’re planning to ride your KX100 in the mountains, it will likely have a lower top speed than if you were riding at sea level.

Or, even if you’re not in the mountains necessarily, but you’re just riding in Colorado, you’re much higher above sea level than the coasts of the US. That will cause your dirt bike to be slower.

Smaller-size bikes (bikes with small cc engines) are more impacted by elevation changes than larger bikes, too. For example, a 100cc bike is more impacted than a 450.

How about the conditions you’re actually riding on or in?

Are you riding in the woods, on a motocross track, or on a paved road? If it’s in the woods, your top speed might be limited. If you’re racing motocross, you can only go so fast while remaining safe and within bounds (and, don’t forget, sometimes slow is fast).

Apart from the elevation and location, another factor that affects the KX100 top speed is the surface on which it is being ridden. A bike ridden on flat pavement will be different than if it were driven on a tight, sandy motocross course; even the type of tires can make a difference.

A Few Other Factors that Can Impact the KX100 Top Speed

Your KX 100 top speed can also be impacted by a few more things, including the condition of your bike, the weather, and how you’re recording the data.

A bike that is regularly maintained will run faster and more efficiently than one that isn’t. For example, a KX100 that has had consistent maintenance done to it will be able to reach a higher top speed than one not taken care of properly.

The weather and temperature can both affect your KX100 top speed. If it rains, the pavement will be wet, or the track and woods may be muddy, and your top speed will probably be lower than normal. Similarly, if it’s an abnormally cold or hot day, that could impact how well the bike is running, which could then lower the top speed.

If you want to get an accurate reading of the top speed of a KX100, use a high-quality onboard GPS device rather than relying on someone pointing a speed gauge at you as you zoom past. This doesn’t mean the bike will actually go any faster or slower, it just changes what you end up seeing on paper.

Ultimately, most people want to know their bike’s rough top speed. Yes, mods and other items impact a KX 100 top speed potential, but at the end of the day, people just want to have an idea of how fast their bike is.

With that in mind, a KX100 top speed is about 65 mph.

Frequently Asked Questions About the KX100 Top Speed