2015 Yamaha YZ125 Race Test | Two-Strokes Live

2015 Yamaha YZ125 huge jump

In the not so distant past, 125cc two strokes were a staple of the motocross world. Every up and coming rider as well as smaller lighter riders spent many hours on them, and as for the last 40 years, the Yamaha YZ125 has been one of the most coveted models and one we looked forward to testing and reviewing.

These days, the 125cc two-stroke has given way to the the 250cc four stroke. Whether that is a good or bad thing is a story for another time. Reflecting the loss of two-stroke options, the 2015 Yamaha YZ125 is the only two-stroke 125 motocrosser to come from Japan. KTM, Husqvarna, and TM are the only other options.

Until 2015, Yamaha hadn’t changed the YZ 125 in a major way. The frame, motor, and bodywork remain unchanged, so the bike looked very dated with plastic that was first seen in 2002. For 2015, Yamaha updated the body work to bring it up to current standards. Fortunately, that’s not all they did.

How does the little two stroke shape up now that it has the sleek look of a newly designed body on an older chassis? Very favorably!

First off, the 2015 Yamaha YZ125 has the most natural feel of any bike I have ridden, and by that I meant that no matter what bike you normally ride, when you jump on the 125, you will feel at home right away.

The bend of the top notch 1-1/8 inch ProTaper fat bars, the seat-to peg-relationship, and even to the firmness of the grips just feels correct from the first ride. Yamaha got it right on the YZ125.

At a claimed 209 pounds wet weight, the YZ125 is the lightest full-sized motocrosser made, and out on the track, that light weight is immediately apparent.

For 2015, the YZ125is equipped with the newest 48mm Speed-Sensitive System forks and KYB’s new shock with internals that are Kashima-coated. The new suspension works great, even though I am well above the target weight for a 125.

Even when flat landing from large jumps and fully bottoming out the suspension, there was no harsh hits – the KYB units just soaked it up. When the track gets rough and hacked out, or in the whoop sections, it’s amazing how fast you can go. Just keep the slightly undersquare mill wide-open, keep your weight back, and you’ll be hitting that stuff faster than you ever thought possible.

A great chassis is only half the battle, of course – the rest is motor. Yamaha has had the same 124cc liquid cooled, reed-valved inducted, power-valved exhausted, two-stroke motor fed by a 38mm Mikuni TMX carb since 2006 with no real changes. In the MX world, that’s ancient, but with no other Japanese players in the 125 game, Yamaha has no reason to spend the R&D dollars on a new motor.

After riding and racing it, though, the YZ125 sure doesn’t feel like it has an ancient motor. Running super clean right off the show room floor, there is no reason for any re-jetting, unless you live at a high altitude.

For those that have never ridden a 125cc MX bike, know that they demand to be ridden aggressively, with a lot of clutch and foot work required to go fast. However, the nice thing about the Yamaha YZ125 is that it’s not hard to keep on the pipe. It has enough bottom-end and revs quick enough that a simple stab of the clutch will get it singing up on the pipe and hauling down the track.

Once there, be ready to shift up; if you rev it too far, the YZ125 falls flat on its face. Keep shifting and you’ll be rewarded with quick lap times. Fortunately, shifting is smooth and precise, while the mechanical clutch pull is smooth and easy.

Test rider Ty Cullins raced the 125 several times with good results. Ty usually races the 250cc class, and after racing the 125 class once, Ty decided to race his usual 250 class. Too our surprise, Ty did just as well as he does on his 250.

What really showed was his corner speed – the 125 loves to take the wide sweeping lines in the corners where the revs can be kept high. The chassis is perfectly happy taking a tight inside line when needed – just better be ready to use a lot of clutch to gain your speed back!

Another nice thing we found when testing in race conditions was how Ty could push hard the whole moto before getting tired. While his lap times were fast with the YZ125, the main problems were trying to pass other riders. Once Ty lost his momentum in a corner behind a slower rider, it was hard to get that speed back and make a pass.

The 2015 Yamaha YZ125’s aluminum rims come shod with the latest Dunlop Geomax MX52 tires, and they worked great for us in a wide range of terrain. The tires eventually wore down, yet they showed no signs of tearing or chunking of the knobs.

Details we like include wide footpegs that keep you stable, a nice gripper seat cover with soft foam that doesn’t let you sink in, comfortable grips and levers, and good brakes with cool wavey rotors. All in all its any easy bike to work on, and maintenance costs are low .

We were disappointed that the blue plastic looks old really fast, the steel sprocket is heavy, and the cheap chain stretches quickly, even with 125cc power. Spring for some Acerbis or Cycra plastic, and Renthal final drive components.

In the end, who’s the 2015 Yamaha YZ125 for?

It is a great bike for a kid coming off a 85cc motocrosser. The youngster will make the transition to a full-size bike much easier than by moving to a 250cc four-stroke.

Also, any rider new to motocross will find that the 2015 Yamaha YZ125 is easier and cheaper to buy and maintain, plus it will keep them out of trouble until they are a good enough rider to make it go fast.

The last potential 2015 Yamaha YZ125 customer is an older experienced rider who has raced everything and is not worried about being the fastest guy on the track. He just wants to be the rider having the most fun, and isn’t that why we all ride?

Photography by Don Williams

Photo rider: Ty Cullins (Endurocross Pro #66; sponsored by Beta USA, Fox, Motorcycle Superstore, Stillwell Performance, Kenda Tires, Motul, FMF Racing)

Location: Milestone MX, Riverside, California

Riding Style

Helmet: Bell Moto-9 Motorcycle-Superstore.com Edition

Goggles: Fox AIRSPC

Jersey, gloves and pants: Fox 360 Flight

Roost deflector: Fox Proframe LC

Boots: Fox Comp 8

2015 Yamaha YZ125 Specifications

Engine: Liquid-cooled 2-stroke; reed-valve inducted

Bore x stroke 54.0 x 54.5mm

Displacement: 124cc

Fuel delivery: Mikuni TMX 38

Ignition: CDI

Transmission: Constant mesh, 6-speed multiplate wet clutch


Front: KYB Speed-Sensitive System inverted fork; fully adjustable, 11.8-inches travel

Rear: KYB fully adjustable single shock with linkage; 12.4-inches travel


Front: Hydraulic single-disc brake, 250mm

Rear: Hydraulic single-disc brake, 245mm


Front: Dunlop Geomax MX52; 80/100-21

Rear: Dunlop Geomax MX52; 100/90-19

L x W x H: 84.1 x 32.6 x 51.0 inches

Seat height: 38.4 incjes

Wheelbase: 56.8 inches

Ground clearance: 14.4 inches

Fuel capacity: 2.1 gallons

Wet weight: 209 lb

Color: Team Yamaha Blue/White

2015 Yamaha YZ125 MSRP: $6390