Yamaha YZ125: Top Speed, Specs & Review

Yamaha possesses huge respect among motorcycle manufacturers worldwide for their world-class models. They are synonymous with high-performance bikes. You will find their models dominating everywhere, from race tracks to dirt trials. Among those bikes, one model might have grabbed your attention. And this is the Yamaha YZ125. Although a beginning model, it is an amazing bike for their dirt bike series. It is no less than a flying tech thanks to the two-stroke engine.

Moreover, this model keeps surprising you when it easily handles all the bumps. Its smooth fork, effective cooling system, and powerful engine ensure smoothness. If you are a bike lover and want to have an insight into this model, this article is like a god-sent. It consists multi-dimensional analysis and review of the Yamaha YZ125. Based on this, the pros and cons and the decree form the later part of this article. So, fasten your seat belts, and begin.

Cursory Glance at the Yamaha YZ125

Yamaha Y 125

Yamaha launched the first model of YZ125 in 1974. There was no change to its frame till 2004. In the frame, visible was a single backbone made of steel. Since this brand uses steel, the previous models were heavier than the later ones. Roughly putting, the steel version weighed around 175 to 200 pounds.

In addition to this, the bike comes with a two-stroke engine. It does use reed valve induction, whose displacement is 125cc. The earlier models from 1974 to 1980 were air-cooled. However, Yamaha began to use liquid cooling from 1981 onwards. When it comes to horsepower, it possesses 35 HP. Low horsepower, you may wonder. Don’t be deceived by it, as this model is a beast and has won several AMA National Motorcross Championships.

Yamaha YZ125 Specs

A brief look at its specs is as follows:


Engine type125cc liquid-cooled 2-stroke; reel-valve inducted
Fuel deliveryMikuni TMX 38
Compression ratio8.6~10.7:1
Bore and Stroke54mm * 54.5 mm
Final driveChain
TransmissionConstant-mesh 6-Speed; multiple wet clutches


Seat height38.6 in
L * W * H84.1 *32.6 * 51.0 inches
Wet weight207 Ib
Fuel capacity2.1 gal
Ground clearance14.4 in
Wheelbase56.8 in
Trail4.3 in


Suspension/frontKYB speed-sensitive system inverted fork; fully adjustable, 11.8-in travel
Suspension/rearKYB single shock; fully adjustable, 12.4-in travel
Tires/front80/100-21 Dunlop MX52
Tires/rear100/90-19 Dunlop MX52
Brakes/frontHydraulic disc 270mm
Brakes/rearHydraulic disc 245mm

Top Speed of the Yamaha YZ125

The maximum speed you can touch while riding this bike is 70 miles per hour. It is slightly over 112 km per hour in terms of kilometers. For a bike that comes with a 125 cc engine, having this speed is quite impressive. However, this speed differs depending on the model year. The weight of this model was increased or reduced several times in the past. These fluctuations in its weight significantly affected its top speed either negatively or positively.

If we talk about the new model of 2022, the top speed you can reach is 70 miles per hour. With the two-stroke 125cc engine, you can outcompete your competitors easily. The reed valve induction system of the YZ125 is responsible for this amazingly fast engine. This bike runs like a beast with an unbelievable bottom end and robust mid-range acceleration.

Now let’s have a detailed review of these specifications and features.

1: Lighter Frame

Lighter Frame

The lighter is the frame of this bike. Unlike previous models, its frame is made of an aluminum alloy, not plastic. Furthermore, its design is race-ready. Therefore, the brand has used the YZ125 for multiple races. In addition to weight, aluminum gives the required amount of integrity. As a result, this semi-double cradle frame is not only flexible but also solid. Since trail ridings are usually quite rough, this frame is ideal for any adventure you want to have. It will not disappoint you.

2: Riders-centric Chassis Design

By just having a glimpse of its chassis, you realize this bike was manufactured with riders in mind. Not only is it extremely user-friendly to avoid fatigue and exhaustion, but it also has an ergonomic design. What is more, the chassis of this bike is so well-tuned that handling and moving it seems effortless. Experienced riders will enjoy riding this bike. It really is fun to ride the YZ125. Last, it also gives you confidence for bigger leaps if you are still learning. In short, its design manifests the expertness of the manufacturers who knew what was required for a comfortable ride.

3: Two-Stroke Engine

When it comes to the engine, it is 125cc. Being a two-stroke engine, it produces more torque in case of high rpm. In fact, more powerful this engine is than four-stroke engines. More than more, Yamaha also switched to liquid cooling in this mode to maintain the heat. The said the cooling system does not let overheat this powerful engine, ensuring a much better acceleration. Hence, the performance is magnificent from any mid to high rpm level.

4: High-Performing Braking System

Brakes are extremely important in trail riding. If they don’t work, death possibly will. Due to this reason, an outstanding braking system is what safety and trail ridging depend on. As far as dimensions are concerned, the front brake of the YZ125 is a 270mm Hydraulic disc brake. While the rear brake is a 240 mm Hydraulic disc brake. With these responsive brakes, you can easily stop the bike at any speed fast.

Braking System

Besides that, reducing unsprung weight on the light wheel is also greatly helpful for the functioning of these brakes. What that means is more speed. On top of that, feel also exists.

5: A New Exhaust System

Dissimilar to the earlier YZ125, the model has a different exhaust. This is because Yamaha is taking a different path with the exhaust. It comes with a brand-new expansion chamber. Except that the design of the exhaust muffler is different. Just like dieting and losing fat, it is also smaller now. Also, the system gives an attractive and slender look. It seems Yamaha perfected this model.

6: KYB Fork-Industry-Leading

What Yamaha did for the fork also deserves love and appreciation. The invented KYB Fork gives you outstanding performance along with being extremely comfortable. With a lead spring, this fork accompanies a speed-sensitive system. With this leaf spring comes the mid-speed valve. That is why it ensures more accurate damping.

This fork also has 11.8 inches of travel, making your ride very smooth. You will also notice how comfortable it is to jump as well.

Want to Increase the Speed of YZ125?

No doubt, the Yamaha YZ125 is an astonishing piece of tech. it is exciting and fun to ride this bad boy. However, fun must be unlimited. You do have mods for having extra fun. Numerous different mods in the market can increase the speed of this bike further. Are they costly?

Increasse speed

There are some suggestions in the latter section about how you can better your Yamaha demon. Do the following:

  • Use a 144cc engine kit
  • Upgrade gear to 13/49
  • Use an upgraded valve system

Given the above-mentioned specs and features, this model has some pros and cons. Based on these, you can make a decision whether you should purchase this bike. The positive and negatives points of the YZ125 are as follows:

Yamaha yz125 seat height

A Yamaha YZ125’s seat height is approximately 38.6 inches. This seat height can be beneficial for riders who are taller or have longer legs because it allows them to reach the ground comfortably and keep their balance while riding. A higher seat height might also give you better visibility and control when you’re jumping or navigating rocky terrain. Despite the fact that the typical height for a dirt bike is between 34 and 37.5 inches, the Yamaha YZ125’s seat height is above the bar.


  • Powerful engine
  • It gives an exciting riding experience
  • Superior handling
  • Adequate weight
  • Low cost for maintenance


  • Lacks bottom end
  • Not an option for beginners

What about other models?

As you are aware, the Yamaha YZ125 is a powerful motorcycle built with experienced riders in mind. It is better for racing and other activities because it has a 125cc engine with a 47-horsepower capacity. Compare it with a trail bike like the Yamaha TT-R230, which has a high ground clearance and is suitable for both on- and off-road travel. You’ll discover that it may also be used effectively by rookies, which is an upgrade.

Bottom Line

In short, the Yamaha YZ125 is a powerful machine with robust features and specs. Its engine’s comfort level and robust power are difficult to meet. This lets you enjoy a comfortable and exciting ride. However, this bike is unsuitable for beginners.

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