What Size Dirt Bike Do I Need? – Dirt Bike Size Guide

Figuring out the best dirt bike size can be challenging, especially for someone who never owned one before. In this post, you’ll learn various factors that you need to consider when choosing a dirt bike that’s right for your body and skills.

Dirt bikes can be for adults and children. So, naturally, your first step is to know who’s going to ride it—an adult or a child? On average, adult dirt bikes measure 85.7 inches long, while kids dirt bikes measure 56 inches long.

Of course, there’s more to dirt bike sizing than knowing a rider’s age. Learn more about it in the sections below.

Factors that Determine Correct Dirt Bike Size

A dirt bike that perfectly suits your height and stature will help you feel comfortable, confident, and safe at all times while riding it. When buying a dirt bike for yourself or your child, it’s prudent to seriously consider these key factors:

Age

So, are you going to buy a dirt bike for yourself or your young one?

Dirt bikes are either made for adults or children. The average-size adult can ride on dirt bikes for children. However, depending on an adult’s height and weight, it’s not going to offer the most comfortable ride. Realistically, mini dirt bikes are best suited for children and teenagers.

Children as young as three years old can start on an electric dirt bike before transitioning to a 50cc dirt bike with training wheels (gas-powered). Dirt bikes for children usually have a seat height of 18 to 34 inches, with an engine displacement ranging from 50cc (cubic centimeters) to 150cc.

Note: Engine displacement refers to the total volume air/fuel mixture an engine is capable of drawing in per revolution.

Height

Choosing a dirt bike that fits your or your child’s height is one of the most important factors you should carefully take into account. A dirt bike that’s too high or too low can be dangerous for different reasons:

  • Controlling it might be difficult, which may lead to injuries.
  • In kids, a dirt bike that’s shorter for their height could cause muscle problems.
  • If you lower a dirt bike to touch the ground better, you could lose ground clearance.
  • If you’re going to buy this for your child, remember that you shouldn’t get one that he or she’s going to outgrow after a few months. As much as possible, the size of a dirt bike should correspond to your child’s height now and in the years to come (around two to three years).

Here’s the rule of thumb: Your feet should should be in a tiptoe position. Meaning, they should touch the ground. However, they shouldn’t be completely flat while on the ground.

Weight

Weight (yours and the dirt bike’s) has a significant impact on the performance of dirt bikes. To be more specific, it affects their acceleration and maximum speed.

The golden rule is the heavier the load on a dirt bike, the slower it accelerates. This is exactly why dirt bikes with the same engine power, but with different weights will accelerate and reach maximum speed differently.

For instance, there are two dirt bikes with a 300cc engine. One weighs 256 pounds, while the other weighs 248 pounds. Expect the 248-pound dirt bike to reach maximum speed and accelerate slightly faster because of its weight.

Aside from your weight, other major factors that determine how much a dirt bike can handle include:

  • Its weight and frame
  • The engine in cubic centimeters (cc)
  • The engine cycle (whether it’s a two-stroke or a four-stroke)

Most dirt bikes are able to handle riders who weigh less than 320 pounds. However, if a rider exceeds this weight limit, tweaking a dirt bike’s suspension might be necessary.

What if you get a dirt bike that has a more powerful engine? You can do that, but make sure your weight can safely handle it.

For instance, you weigh 150 pounds then you bought a 250cc dirt bike. Chances are you won’t be able to control it. Plus, you’ll put yourself at risk for injury

Engine Size

Whatever your height, weight, or body frame may be, you need to pay close attention to a dirt bike’s engine displacement. The bigger the displacement (or capacity), the more powerful an engine can be.

The first thing you need to do is to determine what internal combustion engine (two-stroke or four-stroke) and engine size you need. The correct choice will depend on your age, skill level, and weight.

Between age and experience, the latter is a more important consideration. Let’s say you’re 25 years old and new to dirt biking. You’ll definitely struggle to ride a 450cc dirt bike. Meanwhile, a 14-year-old with more experience than you won’t have problems handling a dirt bike with the same engine capacity.

The table below will give you a good idea of the engine capacity that fits your or your child’s age or height.

Age/Height (Feet and Centimeters)Engine Capacity (Cubic Centimeters)
3-6 years old50
5-8 years old50
8-9 years old110 and 125
9-10 years110
5’10” (178 cm)250
5’8” (172 cm)125 and 150
5’6” (167 cm)140 and 150
5’4” (162 cm)140
5’2” (157 cm)125
6’ (182 cm)450

 

Experience Level

You should always take your skills and experience into account since they’ll ultimately determine what dirt bike size is best for you. If a dirt bike’s too powerful, you can end up hurting yourself. If it’s underpowered, going up a hill at a slow speed is going to be difficult.

If you’re a beginner, choose a dirt bike that’s light and has an engine that fits your weight and experience. You have plenty of options:

  • For children ages 8 to 10 years old, they could start with a 50cc to 90cc dirt bike.
  • Older ones (10 to 14 years old) could get a 90cc to 125cc dirt bike.
  • Teenagers (14 to 17 years old) could get a dirt bike with a 150cc to 250cc engine.
  • Adult beginners would do just fine with a 125cc to 250cc dirt bike.
  • However, if you’re returning to dirt biking after a few years of hiatus from the sport, you might be able to handle a dirt bike with a higher cubic centimeter engine (around 450cc).

Note: Don’t overestimate your capabilities. While your level of experience is important, make sure you don’t pick a dirt bike that’s too big or too small, too light or too heavy for your height and weight.

Can You Adjust the Height of a Dirt Bike?

Ideally, you should go to a physical store to personally examine and test the dirt bike you’re planning to buy. This is the most reliable way to find a properly sized dirt bike.

Remember: The right dirt bike for your size should allow you to raise the heel of your foot until only the ball of your foot is touching the ground.

If it’s not possible for you to do that, your next best alternative is to refer to the seat height. This is the measurement of the lowest point of a dirt bike’s saddle to the ground, while it’s in an upright position.

You need to know your correct seat height to make sure you sit comfortably on the dirt bike, get a good ground clearance, and make more room for the movement of the suspension. You can refer to the sizing chart below for the exact requirements by age and height.

Age/Height (Feet and Centimeters)Recommended Seat Height (Inches)
3-6 years old23-24
5-8 years old23-25
8-9 years old24-26
9-10 years old24-26
10-12 years old26-31
5’10” (178 cm)35-39
5’8” (172 cm)34-38
5’6” (167 cm)34-37
5’4” (162 cm)33-36
5’2” (157 cm)31-35
6’ (182 cm)37.5

 

But what if your dirt bike is too high or too low for your height? What can you do?

Fortunately, most manufacturers offer a low-profile seat. This accessory is usually lower and more tapered than the original seat.

On average, a low-profile seat can lower the seat height anywhere between 0.79 and 2 inches (20 and 50.8 millimeters). Others can reduce it by even up to 32.68 inches (830 millimeters).

However, aftermarket dirt bike seats can be expensive. If you want to modify your bike’s current seat to save money, you can. Below are two of the most common methods for customizing your existing seat yourself.

Lowering the Seat Height

There are bad and good effects of lowering the seat height. If you do it right, you can have a dirt bike that suits your short height and handles a bit better in certain situations because of its lower center of gravity.

The downside of a seat height that’s too low is it can make you feel uncomfortable and prone to crashing later. You’ll also have less ground clearance for leaning over in order to turn.

Method 1: Cut the Seat’s Foam

If you don’t want to spend money on expensive suspension options (e.g., longer lowering links), trimming the seat foam is a cheaper option. It’s actually the most popular method of lowering the seat height.

The advantages of using this method instead of using a lowering link or an internal suspension work include:

  • Cutting the seat foam increases the width of the base, which makes it more comfortable.
  • The biggest advantage of learning to cut your dirt bike seat is being able to get the right seat height for your size. This allows you to plant your foot (or feet) firmly on the ground to prevent your dirt bike from tipping over.

Reminders and Warnings:

  • There’s no turning back once you start the process. If you mess up, you’ll end up wasting your hard-earned money. Therefore, it’s a good idea to be conservative with how much foam you shave off the seat.
  • Depending on your desired height, you can lower the seat anywhere between two to three inches.
  • Working with an older seat foam is harder because of the deterioration. We suggest you buy a new low-profile seat instead of doing this.

People have different ways and tools they use to cut seat foam. The steps and tips below only serve as a general guideline. Feel free to tweak some of them to fit your specific needs.

  1. Mark the areas on the foam that you need to shave off way ahead of time. You can use a permanent marker, but it would be better to use two markers with different colors.
  2. Secure the seat foam to prevent it from moving.
  3. Then, cut off the areas you’ve marked. As much as possible, start against the bottom (the seat pan area), not the top.

You can use a hacksaw blade, electric knife, or large serrated bread knife. Between the three, the electric knife works great, especially if you need to remove plenty of depth.

For this part of the process, you’ll need a lot of patience. Take your time in cutting small amounts of foam at a time, so it’s easier to correct mistakes. You can typically shave off around 1 to 1.5 inches from the center of the seat foam and still have enough left.

Note:

  • It’s okay if there are small air pockets in the foam while you’re cutting it. A good solution is to cover the area with a low-density foam sheet (around 1/4-inch thick) to further smooth the final surface.
  • Use a spray adhesive to glue the foam sheet to the final-shaped seat foam.
  1. Now, it’s time to smooth it down with a sand paper (#60-#180 grit), power sander, sanding block, or hand-held electric belt sander. Use a very coarse sand paper (#60-#80) then shift to a fine sand paper (#120-#220) to get a smooth finish.

A hand-held electric belt sander or sanding disc works great for shaping the edges of the foam. You could probably rent one of these from a local home improvement store, like Lowe’s, or a local rental store.

  1. Place a heavy-duty plastic sheet (e.g., thick trash bag) between the shaped foam carcass and the seat cover. This step is optional, but it would greatly help prevent mildews from forming.
  2. Before reinstalling the seat cover, spread it out in a warm room or in the sun to smooth out any creases. You can use an electric or pneumatic staple gun with 3/8-inch-long staples.

Is a pneumatic staple gun better than an electric staple gun?

Between the two, a pneumatic staple gun is usually more powerful. The downside is you’ll need an air compressor to run it. A commercial-grade electric staple gun doesn’t have the same issue. You only need to plug it into an electric outlet and start sinking staples into tough materials.

Note: If the seat cover is already worn out, you might want to purchase a new one.

Method 2: Make Small Holes

Another way of reducing seat height is drilling small holes in the bottom of a dirt bike’s seat foam to remove the core. This method isn’t only easy, but it also gives you instant positive results. In fact, some people think it reduces seat height much better than shaving off the seat foam.

So, why does it work?

Because of the small holes you’ve created, the foam becomes softer and sinks further. This gives a significant difference in the seat height while riding.

Aside from patience, accurate measurement is a must for this method. Even if you drill only an inch lower, it’s already going to cause a significant impact.

Materials:

  • Power drill (or a foam hole cutter) with a 1-inch or 2-inch keyhole drill bit
  • Pulling pliers, a flat head screwdriver, or an upholstery staple remover
  • Electric or pneumatic staple gun
  • Heavy-duty, rust-resistant staples (1/4-inch)
  • Adhesive, like a bottle of rubber cement
  • Any tool for removing the foam cores (e.g., pliers)
  • Permanent marker
  • Safety glasses

Steps:

  1. Find a comfortable place to perform this process.
  2. After removing the seat from your dirt bike, remove all of the staples from the underside of the seat.
  3. Remove the seat cover, which might’ve been glued in place from the factory. Don’t rush this step.
  4. Like the seat cover, the foam might be glued to the base. Make sure you separate it from the seat base carefully.
  5. Mark the spots where you need to drill the holes. You could make around three rows of five to six holes in the main sitting area of the seat, where there’s plenty of cushioning.
  6. Start drilling or cutting holes into the material. The holes should be shallow at first. There should be at least one inch left of the foam at the top portion of your dirt bike seat. The last thing you want is to see those holes through the seat cover.

Tip: You can use a toothpick (or something similar) with a one-inch mark to know the depth of the remaining foam. Stick it into the foam until the one-inch mark reaches the bottom of the hole. If it doesn’t level with the bottom of the hole, remove more foam.

  1. After pulling the foam you cut, it’s time to reattach the customized foam to the seat’s base. You can use a rubber cement as an adhesive.
  2. Now, one of the trickiest parts of the process: reattaching the seat cover to the base of the seat:
  • Get your seat cover, and then slide the front pocket towards the front end of your dirt bike seat.
  • Flip the seat cover, while making sure it fits correctly.
  • While holding it tightly in place, shoot three to four staples into the front then do the same thing to the back part of the seat.
  • Pull the seam slightly towards the end of the seat then secure it with a pin.
  • Staple it in place.
  • Inspect the sides of the foam.

Raising the Seat Height

Method 1: Buy an Aftermarket Seat

The easiest way to raise the seat height of a dirt bike is to buy a taller aftermarket seat. There are many good choices out there, such as the KTM PowerParts Factory High Seat and the KTM PowerParts Extra High Seat.

The KTM PowerParts Factory High Seat is 20 millimeters (0.79 inches) higher than the standard seat. The KTM PowerParts Extra High Seat is 35 millimeters (1.38 inches) higher than the standard seat and is best for riders who stood taller than 6’3” (1.90 meters).

After replacing the old seat with a high seat, you could also use taller handlebar mounts or bar mount riser clamps. When we say “taller,” we’re referring to the height and rise of a handlebar.

You measure a handlebar’s height from the end part of the bar (or control length) to the clamp area. Meanwhile, the measurement of the rise of a handlebar starts from the clamp area to the bar end (or the first steep bend).

Method 2: Adjust the Sag Settings

Sag may refer to free sag or race sag. The former measures the sagging of a dirt bike when it’s stationary on the ground, without you on it. The latter measures the same thing, but with you sitting on it.

Here’s how to measure and adjust the sag of your dirt bike:

  1. Place your dirt bike on a stand. Make sure the rear wheel is not touching the ground.
  2. Measure from the rear fender to any spot on the rear axle. You’re going to be using the same spots later for consistent measurement.
  3. Write down the measurement in millimeters.
  4. Remove your dirt bike from the stand then sit on it, while wearing your full riding gear.
  5. Have someone hold your dirt bike for you, so you’re free to put your hands on the handlebars and your feet on the pegs.
  6. Bounce your dirt bike a few times to determine the settling point.
  7. Again, have another person measure the distance between the rear fender and rear axle.
  8. Subtract the free sag and race sag measurements. In general, the difference should be approximately 100 millimeters. However, you’re free to tweak the result to fit how you want your dirt bike to handle for improved stability. But to be sure, check the owner’s manual.
  9. You can adjust the sag amount by adding or removing preload to the spring in your suspension. You’ll only need basic tools for the job, such as a Japanese dirt bike hammer and punch for the spring adjustment. Or, if you have a European dirt bike, you’ll need an Allen and a punch to move the spring adjuster.

Conclusion

In general, shopping in person is the best way to pick and buy a dirt bike. It allows you to sit on the dirt bike you want to buy, with the ball of your foot and toes touching the ground. That’s the dirt bike that’s perfect for you.

Buying a dirt bike doesn’t need to be an expensive mistake. Before committing to the purchase, and if you can’t go to your local dirt bike shop, we hope you think about our tips and information to help you find the dirt bike size for your height, weight, and experience.