KLX 140 Top Speed: How Fast is This Pit Bike?

If you ride a dirt bike, even a trail bike like a KLX 140, you’re almost guaranteed to want to know how fast it goes. As dirt bike riders, we need to know how fast our bikes go. In this article, we’ll be covering the top speed of KLX 140.

KLX 140 Top Speed

Kawasaki has long been one of the dominant players in the dirt bike world, especially in the youth motocross bike world, and of course, the pit bike world, with bikes such as the KLX 140.

At least, I consider the KLX140 a pit bike… it’s on the bigger side for pit bikes, but I have seen it as a common step-up for riders where the 110 is too small for them, or they just want something slightly bigger.

What does this mean for the KLX 140 top speed?

The KLX 140 top speed is about 50 mph.

This is about 5 mph faster than the KLX 110 top speed. It’s also about the same as the TTR 125 top speed (the TTR125 does about 45-50, so it could be the same or 5mph faster — regardless, they’re close).

Why did I pick these two bikes to compare the KLX 140?

The KLX 110 was chosen because, as I mentioned, the KLX 140 is often the bike KLX 110 riders will get if they start to feel like the 110 is too small. When adults ride pit bikes, especially 110s, it doesn’t usually take too long before they realize they’re too small and they’d like something bigger. That bigger choice is often a KLX 140 — at least for Kawasaki riders.

I’ve seen it firsthand with one of my best friends.

I rode his KLX140 and it was a lot more comfortable than my KLX110. The bigger wheels and better suspension were awesome, but the bike felt really slow compared to my 110. The extra weight of the KLX140 didn’t seem to outweigh the extra 30 cc’s the bike has over the KLX110.

A TTR 125 was chosen to also compare the KLX140 to because it’s a similar bike, but from a different manufacturer — Yamaha. People tend to like to see how these types of bikes stack up against one another between brands. Also, the TTR 125 is sort of between the KLX110 and the KLX140.

What changes the top speed of KLX 140?

Calculating the true top speed of a dirt bike can be challenging due to various factors that can impact it. Let’s take a look at some of these factors.

Modifications

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

If your KLX 140 has engine work (especially a big bore kit) and a pipe, that’s not really comparable to the top speed of a stock KLX 140.

The top speed of KLX 140 that hasn’t had any work done to it will be significantly lower than the top speed of a bike that has undergone mods.

The more work you do to the bike, the greater the difference in speeds will be.

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

Gearing

The second most important factor in determining the KLX 140 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 14-tooth front sprocket and a 51-tooth rear sprocket (depending on the year of your bike).

Riders normally pick different gearing depending on the situation they’re riding. If the rider is racing supercross (which they wouldn’t do on a KLX140, but for illustrative purposes, stick with me…), they would typically want more acceleration (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 on 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 that of supercross or motocross.

This might not sound like much to some people, but it has a large impact on the top speed of any dirt bike. Depending on the gear changes made, it can increase or decrease the KLX 140 top speed by more than a few miles per hour.

A KLX 140 with a 6-tooth front sprocket will have a different top speed 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 KLX 140….).

Additionally, a change to the front sprocket has a great effect on the top speed and bottom end 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

The top speed of KLX 140 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 top speed is going to be.

In addition, an experienced rider can make the KLX 140 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.

Riding Conditions

The KLX 140 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 KLX 140 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 parts of Utah or Colorado, you’re likely much higher above sea level than the coasts of the US. That will cause your top speed to be lower.

Smaller-size bikes (bikes with small cc engines) and bikes with less power (a trail bike versus a race bike) are more impacted by elevation changes than larger bikes, too. For example, a KLX140 is going to be more impacted by elevation than a KX250F motocross race bike.

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 top speed is the surface on which it is being ridden. The top speed of KLX 140 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.

Other Factors Impacting the KLX 140 Top Speed

Your KLX 140 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 KLX 140 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 KLX 140 top speed. If it rains, the pavement will be wet 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 KLX 140, use an 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.

Waving the White Flag on the Top Speed of KLX 140

As we pass by the white flag of this article and enter into the last lap, I want to summarize what I’ve covered so far.

Ultimately, most people want to know their bike’s rough top speed.

Yes, mods and other items impact a KLX 140 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 KLX 140 top speed is about 50 mph.

Frequently Asked Questions About the KLX 140 Top Speed