2018 Yamaha YZ125 Review | Two-Stroke MX Lives

March 2, 2018

2018 Yamaha YZ125 Review | Two-Stroke Motocrosser

The Yamaha YZ125 has been a long time staple of the Yamaha line up—it first showed up in Yamaha showrooms in 1974.

For the first 30 years of its life, the YZ lived in the highly competitive world of 125cc motocrossers, where it had major competition from the other three Japanese manufactures and KTM.

That came to an end with the four-stroke revolution in the mid-2000s, and the displacement equality MX.

With 250cc four-strokes exceeding the power of the 125s, the two-strokes quickly disappeared from professional motocross and, soon after, were gone from Honda’s, Suzuki’s and Kawasaki’s line ups. At the time, the YZ125 was generally considered the top 125.

Yamaha has never given up on the 125cc two-stroke. It received a new frame in 2005, a new motor the following year, and all-new body work in 2015. Along the way Yamaha always equipped it with quality KYB suspension, as well as making many small updates to the internals of the motor.

To keep the YZ125 relevant, it gets contemporary components such as Pro Taper fat bars, the latest Nissin brakes, wave rotors, a gripper seat cover and Dunlop Geomax MX52 tires mounted on Excel rims. For 2018 the only change is the rims are now blue. While that is not a functional update, it gives the latest YZ a cool modern look.

Riding the 2018 Yamaha YZ125 is everything we have come to expect out of a small displacement two-stroke, and that is a good thing! With no major changes over the last several years, and having tested previous versions, we are pretty familiar with the YZ.

The 125cc power-valve equipped motor is the easiest to ride 125 MX bike we have ridden. While it’s still like all other 125 two-strokes and demands to be ridden at high rpm, it is the ease at which you can do it that makes the YZ so good. For a 125, it has an extremely wide powerband. It’s easy to get up on the pipe and keep it there while shifting through the silky smooth 6-speed transmission.

Like all 125s, the 2018 Yamaha YZ125 requires a good amount of clutch work, which you won’t mind at all. The easy-pull clutch never faded on us. Add to it a perfectly jetted 38mm Mikuni TMX carburetor and the Yamaha powerplant is very easy to live with.

On the chassis side, it’s pretty much the same story. With a frame that was designed in 2005, it doesn’t have quite the modern feel of some of the bikes with newer designs, but it does everything really well.

With a very light claimed wet weight of 207 pounds, the YZ125 is nimble and easy to rail into a corner. You can really push this bike hard into corners and still get it laid over and turned without any drama.

On the other end of the spectrum, we can’t say it is an extremely stable bike. However, the light weight gives you confidence, so you don’t care. By that we mean you can hold it wide open down a rough straight with the bike dancing side to side as a 125 will tend to do, and you still have no problem pushing it faster. If this were on a heavier, larger-displacement bike, it would scare you and you would want to back off.

Suspension is an area Yamaha motocross motorcycles have really shined the last several years, and the 2018 Yamaha YZ125 has a KYB SSS (Speed Sensitive System) front fork, along with a KYB shock that has includes low- and high-speed compression damping adjustability.

Put that great suspension on a lightweight chassis and you have an awesome chassis. With my son and I a good 20 to 30 pounds over the target weight of a 125, we could feel that it was a little on the soft side. Yet, it still had no harsh bottoming or feeling like the bike was wallowing around as other bikes with soft suspension do. It still felt great.

Although the 2018 Yamaha YZ125 is an excellent race bike, it would be nice if Yamaha gave the YZ125 a major update with a little more power, a truly modern chassis, and plastic that doesn’t look old after just a couple rides.

For now, we’re just glad they kept it around all these years and we get the opportunity to rip on it, and buy one for just $6499.

Photography by Don Williams

RIDING STYLE

Helmet: Bell Moto-9 Carbon Flex
Goggles: Fox Air Defence
Jersey + Pants: Fox 360 Preme
Gloves: Fox Airline Race
Boots: Fox Instinct

2018 Yamaha YZ125 Specs

ENGINE

Type: Two-stroke
Displacement: 125cc
Bore x stroke: 54.0 x 54.5mm
Compression ratio: 8.6:1 to 10.7:1
Fueling: 38mm Mikuni TMX carburetor
Intake: Reed valve
Port timing: Power valve
Lubrication: Premix

CHASSIS

Frame: Aluminum
Front suspension; travel: Fully adjustable KYB Speed-Sensitive System inverted fork; 11.8 inches
Rear suspension; travel: Linkage-assisted, fully adjustable KYB shock; 12.4 inches
Tires: Dunlop MX52
Front tire: 80/100 x 21
Rear tire: 100/90 x19
Front brake: 270mm disc
Rear brake: 245mm disc

DIMENSIONS and CAPACITIES