Yamaha YZ125

Are you looking to move up from an 85 or supermini? Maybe you’re looking to buy your first dirt bike? Has the Yamaha YZ125 caught your attention, but you’re not sure if it’s the right bike for you?

This Yamaha dirt bike is a highly versatile machine, suitable for riders with every kind of experience.

In this article, I will tell you about my experience with this bike so that by the end, you will know what it’s capable of and whether or not it’s the right fit for you.

Yamaha YZ125 – A General Overview

The Yamaha YZ125 is a dirt bike with a high mid-top power delivery manufactured specifically for dirt bike racing. It has a 2-stroke, 125cc, liquid-cooled engine with 35 horsepower and a top speed of about 65-70.

Yamaha YZ125

The bike has been upgraded several times since its first release in 1974, but the 2022 model received the most significant upgrades in recent years. The bike remained relatively unchanged from 2000 to 2021.

The YZ125 is an excellent bike for beginner dirt bike riders and experienced riders who just want to have relaxed, more controllable trail bike riding.

There is another dirt bike, the TTR125, also by Yamaha. In the next section, I will distinguish the two clearly, so you’ll know the main differences.

Difference Between the YZ125 and the TTR125

While the YZ125 has a 2-stroke engine, the TTR125 has a 4-stroke engine operation.

Because of the completely different engine operation, the YZ125 is a more powerful bike. It can deliver higher mid-top power and has a longer-lasting torque delivery.

On the other hand, the TTR125 is significantly less powerful. Even though the bikes have the same displacement, the 4-stroke engine on the TTR125 has a softer power delivery, making it an ideal bike for learning and trail riding (not racing). 

That is why, if you’re a beginner, I would recommend getting the TTR125. Many experienced riders also recommend it for beginners and teenagers because of its low performance and gradual power delivery.

On the other hand, the YZ125 is a more powerful bike with high power delivery and rapid acceleration. It has been built specifically for dirt bike racing, where speed and torque are important factors.

YZ125 Components and Specifications

Now that you have an idea of how powerful this bike is and how it differs from the TTR125, let’s look at its components and specifications in more detail.

I will review the new and redesigned 2023 YZ125 model and its characteristics.


As I’ve already said, the YZ125 has a 2-stroke, 125cc, liquid-cooled engine capable of delivering an impressive 35 horsepower.

The cylinder has been redesigned and leaned forward and has a bore of 54 millimeters and a stroke of 54.5 millimeters. The maximum compression ratio calculated by these values is between 8.2-10.1:1, which is why the bike has a high horsepower output.

The intake reed valve (YPVS – Yamaha power valve system) has been improved. It’s more lightweight and resilient, delivering better throttle response at lower RPMs. This makes the bike “gentler” for beginner riders.

The entire gas-air-oil mixture is premixed in the Keihin PWK38S/1 carburetor. The number 38 signifies the diameter of the carburetor’s intake hole, measured in millimeters. 

The 38 millimeters carburetor size is the most popular and provides all-around power, making this bike versatile on the track.


The YZ125 has a constant mesh, 6-speed transmission gearbox. The lay shaft is in constant mesh with the output shaft, and the gears are helical. This means that the power transmission from the engine to the output shaft is done through the layshaft.

The transmission gears have been redesigned with improved mechanisms for smoother shifting. The connecting rod is 8 millimeters longer as well, providing more torque at lower engine RPMs.

The power delivery to the rear wheel is done via a chain and sprockets (13 teeth in the front, 49 teeth in the rear), which have also been improved and their weight reduced.


The suspension is one of the best parts of the YZ125. 

Premium suspension manufacturer KYB has been making suspension parts for the YZ125 for decades, and they’re even better in the 2022 model. 

It doesn’t matter if you’re a lighter or heavier rider, as the suspension on the YZ125 can handle everything from 150 to 190 pounds. This is due to the 4.3N/mm suspension in the front forks and the 48N/mm suspension in the rear spring.

The front suspension consists of upside-down forks with a travel of 300 millimeters. The rear suspension consists of one swing arm with a travel of 315 millimeters.

The YZ125 has the same suspension parts as most of Yamaha’s 4-stroke dirt bikes.


The frame of the YZ125 is a semi-double cradle. It’s made up of two parts.

The front part that connects to the front suspension gives the bike a caster angle of 26° and a trail of 109 millimeters.

Yamaha has used this frame construction for the YZ125 because it provides durability and stability while making the bike more lightweight.

Unfortunately, the YZ125 isn’t among the lowest bikes out there. The seat is quite high, at 980 millimeters, which makes the bike exclusively suitable for taller riders. 


Brembo manufactures both the front and rear brakes for the YZ125.

The brakes are hydraulic, with a single disc at the front and the rear. The front disc diameter is 270 millimeters, while the rear disc is 240 millimeters.

The real stopping power of this bike comes from the front brake due to its dual-piston brake caliper and powerful grip. 

The rear brake comprises a single-piston caliper, providing excellent stopping power for low-speed cornering and stability maneuvers.


Since this is a dirt bike, the front wheel and tire are larger than the rear one. 

The front tire (80/100-21) has a width of 80 millimeters, an aspect ratio of 100 millimeters, and a rim size of 21 inches. It has a load index of 51 and an “M” speed rating.

The rear tire (100/90-19) has a width of 100 millimeters, an aspect ratio of 90 millimeters, and a rim size of 19 inches. It has a load index of 57 and an “M” speed rating.

The bigger front wheel provides increased stability for off-road riding, while the increased width of the rear tire provides better grip and traction with the surface.

How Well Does It Ride?

Fortunately, I could ride the YZ125 and see how it handles.

When I saw the bike, I was impressed by the build quality.

As for riding it, I immediately noticed how much power the engine delivered. Even though it was smooth at the start, I could reach a top speed of up to 65-70 miles per hour.

What impressed me was the shock absorption. The KYB suspension was flawless and provided excellent suspension, despite my weight of 175 pounds. The wider seat added to the overall riding comfort as well.

Overall, the bike provides exceptional handling and inspires confidence from the moment you sit on it. I’ve passed through corners with little effort, and the bike’s lightweight feels like you’re riding a 35-horsepower bicycle.

The YZ125 is a versatile all-conditions bike, offering durability and high power output. It is a bike that certainly impresses many riders but one that is not suitable for all of them.

Now that you know how capable and versatile the YZ125 is, are you convinced that it will fit your riding style and preferences? 

Or will you choose another, less-powerful dirt bike for more relaxed off-road riding?

Let me know your thoughts, and leave a comment below.

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About Frank Diaz

Hi everyone, my name is Frank Diaz and I am the face behind GaragestPicks. I studied Mechanical Engineering at Georgia Institute of Technology and worked as a mechanic for over 20 years. I love working on cars and doing DIY projects around the house. I write this blog to share my knowledge and help others fix their cars with most common tools.

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