The battle between KTM 125SX VS YAMAHA YZ125

dothang31/10/2023

234 13 minutes read

The battle between KTM 125SX VS YAMAHA YZ125

Introduction

In the world of motocross, finding the perfect bike can be a daunting task. Two popular options for riders looking for a 125cc two-stroke machine are the KTM 125SX VS YAMAHA YZ125. Both bikes have a solid reputation and offer impressive features. In this blog post, we will compare these two motocross bikes to help you make an informed decision on which one is best suited for your riding style and preferences.

Design and Appearance KTM 125SX VS YAMAHA YZ125

The design and appearance of a motocross bike can play a significant role in attracting riders. The KTM 125SX features the brand’s signature orange color scheme, sleek bodywork, and aggressive styling. The bike exudes a sense of power and speed, with its high-mounted exhaust system and sharp lines.

On the other hand, the 2020 Yamaha YZ125 showcases the iconic blue color scheme that Yamaha is known for. It boasts a more traditional design, with smooth body panels and a low-mounted exhaust system. The overall appearance is clean and modern, appealing to riders who prefer a more understated look.

Engine Performance KTM 125SX VS YAMAHA YZ125

When it comes to engine performance, both the KTM 125SX and the 2020 Yamaha YZ125 deliver impressive power for their respective displacements. The KTM 125SX is equipped with a high-revving 125cc two-stroke engine that produces excellent bottom-end torque and a strong mid-range. The bike’s power delivery is known for being aggressive, making it a favorite among riders who enjoy a thrilling ride.

On the other hand, the 2020 Yamaha YZ125 features a similarly sized 125cc two-stroke engine that delivers smooth power throughout the RPM range. The YZ125 is renowned for its exceptional top-end power, making it a popular choice for riders who prefer high-speed tracks. The bike’s power delivery is more linear compared to the KTM, providing a different riding experience.

Suspension and Handling

When it comes to motocross bikes, suspension and handling play a crucial role in providing a comfortable and controlled ride. The KTM 125SX comes equipped with top-of-the-line WP XACT suspension components. The front fork offers excellent damping characteristics, allowing for precise cornering and superior handling. The rear shock provides excellent stability and absorbs bumps effortlessly.

On the other hand, the 2020 Yamaha YZ125 features KYB suspension components that have been fine-tuned over the years to provide exceptional performance. The front fork delivers a plush feel, providing riders with confidence when tackling rough terrain. The rear shock offers excellent feedback and control, ensuring a smooth ride even in challenging conditions.

Braking System

Having a reliable braking system is essential for any motocross bike. The KTM 125SX features high-performance Brembo brakes, which offer excellent stopping power and fade resistance. The front and rear disc brakes provide consistent and precise braking performance, allowing riders to confidently navigate through corners and scrub speed when needed.

Similarly, the 2020 Yamaha YZ125 is equipped with powerful front and rear disc brakes that deliver strong stopping power. The bike’s braking system offers good modulation, allowing riders to control their speed with precision. Overall, both bikes provide reliable braking performance that instills confidence in riders.

Ergonomics and Comfort

Ergonomics and comfort are vital considerations when choosing a motocross bike, as they directly affect a rider’s ability to maneuver the machine effectively. The KTM 125SX features a slim and aggressive seat design, allowing riders to easily shift their weight while riding. The bike’s handlebars are adjustable, offering riders the option to customize their riding position for optimal comfort and control.

On the other hand, the 2020 Yamaha YZ125 provides comfortable ergonomics with its well-padded seat and rider-friendly layout. The bike’s handlebars are positioned at an ideal height, providing riders with a natural grip and control. Additionally, the YZ125’s overall weight distribution contributes to improved stability and maneuverability.

Price and Value

Price is often a significant factor when making a purchasing decision. The KTM 125SX typically comes with a higher price tag compared to the 2020 Yamaha YZ125. However, it’s important to consider the value offered by each bike. The KTM 125SX boasts premium components, cutting-edge technology, and exceptional performance, justifying its higher price point for riders seeking top-tier features.

On the other hand, the 2020 Yamaha YZ125 provides excellent value for riders looking for an affordable yet reliable motocross bike. Despite its lower price, the YZ125 offers competitive performance and durability that Yamaha is known for.

This is not a shootout between the 2020 Yamaha YZ125 and the 2020 KTM 125SX; it is an unshootout. We will provide you with all the same facts as in a true-to-life shootout, but 125 two-strokes are different from 250 two-strokes, 250 four-strokes, or 450 four-strokes in that they serve a different purpose. For the most part, these three groups of bikes are purebred race bikes, with dedicated race classes where they have a chance of winning.

Not so with a 125 two-stroke. Under the AMA’s convoluted double-displacement handicapping of four-strokes, the number of 125 two-strokes with a ghost of a chance of winning anything above the 125 Novice class is almost non-existent. That doesn’t stop guys from trying to race them. Even without racing acceptance, 125 two-strokes have found a unique audience. They have become the go-to bike for riders who just want to have fun.

The best place to find 125 two-strokes is at a practice track on a Saturday afternoon, where these little bikes shine and their riders enjoy the thrill of going flat out. And, as of late, there are more two-stroke-only races where bikes like the YZ125 and 125SX can compete against other two-strokes. Whether at the World Two-Stroke Championships, Washougal Dream Race, AMA National All-Star series or Marty Tripes Two-Stroke series, race promoters are creating special events for two-strokes.

Thus, the “2020 MXA 125 Unshootout” was born. Want to play ride on a sunny day with your friends? Want to go to the local track and compete against your rivals? Want to build your dream bike for the 2020 World Two-Stroke Championship? Want to relive your teenage years (only without fouling so many spark plugs)? The MXA unshootout is designed to provide you with all the information you need about these two bikes (three, actually, because the KTM 125SX can also be considered a stand-in for the virtually identical 2020 Husqvarna TC125).

HOW MUCH DO THEY COST?

Without the added shipping charges and ridiculous setup fees that make your dealer look like he got his billing protocol from the phone company, the 2020 Yamaha YZ125’s Manufacturer’s Suggested Retail Price (MSRP) is $6,599. That is $100 more than the 2019 YZ125. Not surprisingly, the retail price of the 2020 KTM 125SX also increased by $100 from its 2019 price of $7,199 to the 2020 price of $7,299. The price difference between the YZ125 and 125SX remains at $700.

If price is a concern, the 2020 Yamaha YZ125 is a bargain, and that extra $700 can go a long way towards buying fuel, pre-mix oil, tires, and repairing crash damage. However, if you’re going to spend money on upgrading the YZ125, you would be better off buying the KTM 125SX in the first place.

Nothing matches KTM’s attention to detail – from the Brembo brakes to the high-tech axle blocks.

HOW MUCH DO THEY WEIGH?

Surprisingly, the claimed weights of the YZ125 and 125SX are very accurate. Without fuel in the gas tank, but with all other fluids, the 2020 YZ125 weighs 201 pounds (as claimed). The KTM 125SX weighs a very light 192.5 pounds (slightly over half a pound more than what is claimed in the brochure).

Please note that the KTM 125SX is 7.5 pounds lighter than the YZ125 – even on a 450cc motocross bike, that weight difference is noticeable on the track. The KTM 125SX is the lightest full-size motocross bike made in 2020.

HOW DO THEY PERFORM ON THE DYNO?

If you only look at these two bikes’ stats overlaid on a dyno curve, the Yamaha makes more horsepower from 5000 rpm (which is as low as a 125 two-stroke can actually run) up to 7800 rpm. From 7900 rpm until both the YZ125 and KTM 125SX peak at 11,500 rpm, the KTM 125SX outperforms the YZ125 across that 3500 rpm rev range. At peak power, the KTM produces 37.50 horsepower, while the YZ125 makes 34.84 horsepower. That is a difference of 2.66 horsepower in favor of the KTM.

However, when you break it down into rpm increments, starting at 6000 rpm, the YZ125 has a half-horsepower advantage over the KTM off idle. At 7000 rpm, the Yamaha makes three-quarters of a horsepower more than the KTM. This trend continues for the YZ125 up to 7800 rpm, where it is still more than half a horsepower better than the KTM.

However, at 8000 rpm (where the KTM 125SX powerband kicks in), the orange bike has a little over half a horsepower advantage over the YZ. And it only gets better for the KTM from there. At 9000 rpm, the 125SX has an almost two-horsepower advantage. At 10,000 rpm, it is half a horsepower better. At 11,000 rpm it is almost three horses stronger, and at peak power (11,200 rpm), the KTM produces 37.50 horsepower while the YZ125 only produces 34.50 horsepower.

WHICH ONE MAKES THE MOST TORQUE?

The 2020 Yamaha YZ125 and KTM 125SX reach their peak torque at 11,000 and 11,100 rpm respectively. The 125SX produces 17.69 pounds-feet of torque, while the YZ125 generates 16.29 pounds-feet. This gives the KTM a significant advantage in terms of torque. However, it is important to note that the YZ125 produces more torque below 8000 rpm, while the KTM 125SX performs better above 8000 rpm.

WHICH ONE IS FASTER ON THE TRACK?

There is no need for Sherlock Holmes to solve this mystery. Every MXA test rider quickly realized that the KTM was incredibly fast in the most powerful part of its powerband. They were able to clear big tabletops on the KTM that the YZ125 struggled with. When going up big hills, the KTM 125SX could easily overtake the YZ125. On long straightaways, the KTM left the YZ125 behind. If you are looking for the fastest production 125 two-stroke on the track, look no further than the orange bike.

IS THE 2020 YZ125 ENGINE A DOG?

Far from it. What often gets overlooked is that top speed isn’t everything when it comes to a motocross bike. While the KTM 125SX is extremely fast from 8000 rpm onwards, the YZ125 has a more usable powerband when exiting corners. The KTM requires significant clutch work to get it up to speed, whereas the YZ125 accelerates out of corners with a satisfying pull.

By generating more thrust in the first 50 feet after a turn, the YZ125 often builds up a lead that the high-rpm KTM cannot close. Lap after lap, two MXA test riders would compete with the YZ and KTM. The Yamaha YZ125 would burst out of turns, and the KTM would try to catch up on the straight. If the YZ125 managed to stay in front, eventually the KTM rider would make a mistake on corner exit and have to work hard to regain speed.

The KTM’s hyperkinetic powerband was prone to mistakes at low rpm, while the YZ125 was mistake-free and, even if you made an error in a corner, it would quickly regain power, unlike the KTM 125SX.

WHICH ENGINE WAS MORE FUN TO RIDE?

Without a doubt, every test rider agreed that the YZ125 was easier to ride, less prone to mistakes, and more fun because of its low-to-mid power delivery. The KTM was stressful in tight turns and required a go-for-broke approach, as all passes were made with sheer speed, whereas with the YZ125 passes could be made with racecraft.

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The KTM 125SX is light, agile, and blessed with plenty of top-end power.

WHICH BIKE HAD THE BEST SUSPENSION?

The MXA test riders believed that comparing the YZ125’s Kayaba SSS suspension to the KTM 125SX’s WP XACT suspension would be a waste of time. After all, Kayaba SSS suspension has consistently been rated as the best for the past 14 years. Maybe due to the lightness and reduced power of the 125 two-strokes, the difference between the SSS and XACT suspension wasn’t as significant as it is on 250 and 450 four-strokes.

Two factors were at play here: (1) The loads and stresses on the suspension components are much lower on a 201-pound, under 35-horsepower YZ125 than on a 238-pound, over-58-horsepower YZ450F (or its orange counterparts). (2) One downside of coil-spring forks is that if the spring rate isn’t correct for your weight or speed, it can be difficult to install softer or stiffer springs. On the other hand, air springs can have their spring rate adjusted in minutes. During our testing with riders weighing 130 pounds (Novices), 175 pounds (Vets), and National-speed Pros, we were able to customize the spring needs of each rider with the WP XACT air forks on the spot.

In conclusion, the Kayaba SSS forks worked best for the target audience of a 125 two-stroke, which Yamaha believes to be teenagers in the range of 130 to 150 pounds. However, they were still adjustable for riders of different weights. Heavier test riders preferred the 48mm WP XACT air forks for obvious reasons.

As for the shocks, the test riders felt that both the Kayaba and WP shocks performed equally well overall but again, performance was dependent on rider weight.

WHICH BIKE HANDLES BEST?

We are amazed that the 14-year-old chassis of the YZ125 still handles like a modern machine. It has a few quirks from its 2005 inception, but overall, it is a solid chassis that corners well, remains stable at high speeds, and feels well-balanced. There are no major complaints about the YZ125’s frame geometry, although there is also nothing exceptional to boast about.

However, despite its advanced age, it outperforms many of the frames released in the 2020 model year. That being said, it is still not better than the 2020 KTM 125SX chassis. The KTM’s chromoly steel frame is more resilient, offers a more organic feel, turns smoothly, and excels in navigating ruts. There is no chattery feedback from the front end when leaning into turns. However, most of the KTM’s capabilities come to the forefront when pushed hard by the rider.

The Yamaha chassis has proven to be reliable, with a good fit for various conditions. The main drawback to the Yamaha’s handling is that it comes with three-generation-old Dunlop MX52 tires on both the front and rear. The front tire is not as predictable as the two-generation-old Dunlop MX3S tires on the KTM 125SX. The MX3S is an excellent front tire, but it was discontinued by Dunlop due to side knob shedding issues when ridden on hard-packed dirt. From a handling perspective, we would prefer the MX3S over the MX52.

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WHAT THE MXA TEST RIDERS THOUGHT

“The YZ125 was more enjoyable to ride. It felt sharper and had a smooth power delivery from low to mid-range. If I made a mistake in a corner, the YZ125 would correct it. The KTM felt better in corners, but because you had to throttle hard out of tight corners, it was easy to fall off the powerband.”

“The KTM 125SX was significantly faster than the YZ125. It had more top-end power, revved up quicker, and seemed to have a longer powerband. The YZ125 relied mostly on its low-end power. It had quick response initially, but after that, you would wait and see if the KTM would blow past you once the Yamaha’s power flattened out.”

“I would probably gear down the KTM by one tooth to improve low-end throttle response, especially on short run-ups to jumps.”

“Yamaha’s front brake was much better than I remembered. It wasn’t as solid as Brembo brakes, but it had a nice feel and good modulation. That was important because when racing against a 250 four-stroke, you have to brake late and take advantage of the freewheeling two-stroke engine and lightweight chassis. Otherwise, they will out-accelerate you on corner exit unless you dive bomb them in the last few feet.”

“I preferred the KTM’s lower handlebars over the YZ125’s bars, probably because the YZ125’s bars were taken from the YZ250 and felt slightly too tall. Another thing that bothered me was the bottom subframe bolt on the left side of the bike. My boot kept hitting it because it sticks out too far.”

You wouldn’t know it was a 14-year-old engine on the track.

“If I were buying a bike for recreational riding, I would choose the YZ125, keep it stock, and be happy with it. However, I wouldn’t choose it for racing.”

“Would it hurt Yamaha to give the YZ125 a more modern appearance? Yes, they switched to Arrow plastic in 2015, but that was five years ago, and even the YZ250F and YZ450F have moved away from that look.”

“There were no carburetor issues with either the YZ125 or KTM 125SX. This wasn’t true when KTM initially switched from Keihin to Mikuni carburetors. Now both the YZ125 and KTM 125SX have the same carburetor.”

“With the same run-up and distance to the jump, I could clear everything on the KTM. Occasionally, I came up short on the YZ125.”

“I have to believe that the 2006 Yamaha YZ125 must have been an incredible machine back in its day because it still performs at such a high level even after all these years with minimal changes.”

WHAT DO WE REALLY THINK?

If you ride 125s for fun and enjoyment, go for the YZ125. It offers enough value for your money to satisfy anyone looking to have fun on one of the best motocross bikes ever made.

If you’re racing a 125 to improve your skills, win races, and not compromise any performance compared to your competitors, choose the KTM 125SX. It is a superior racing bike compared to the YZ125—and any attempt to make the YZ125 as fast, light, and agile as the 125SX will end up costing more than the $700 price difference.

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Conclusion

When it comes to choosing between the KTM 125SX and the 2020 Yamaha YZ125, both bikes have their strengths and cater to different riding preferences. The KTM 125SX is known for its aggressive power delivery, superior suspension components, and customizable ergonomics. On the other hand, the 2020 Yamaha YZ125 offers smooth power delivery, excellent top-end performance, and comfortable ergonomics.

Ultimately, your choice should be based on personal preferences, riding style, and budget. Whether you’re seeking pure adrenaline on the track or looking for a reliable machine that won’t break the bank, both bikes have something unique to offer. Test riding each bike can provide valuable insights into how they suit your individual needs before making a final decision.