2020 Yamaha YZ125X Review First Ride

Riding Yamaha’s 125cc two-stroke off-road motorcycle in South Carolina.

Proving that Yamaha is listening to its consumers, the tuning fork guys are once again expanding their competition cross-county model line with another competitively priced model—the YZ125X. For 2020, Yamaha took a look at something it was missing in its off-road motorcycle lineup and filled the gap with a bike that is designed to be the perfect step up to a full-size cross-country machine. Yamaha engineers sought to optimize the YZ125X for the unique demands of hare scrambles and GNCC racing, and while at first glance it appears to be very similar to its motocross counterpart, the YZ125, it is what you can’t see that really makes the difference.

Riding the 2020 Yamaha YZ125X at Randy Hawkins’ private ranch in Union, South Carolina.
Riding the 2020 Yamaha YZ125X at Randy Hawkins’ private ranch in Union, South Carolina.Mike Vizer

As I got ready to ride the YZ125X, I was excited but also did not set my expectations too high. I am only referring to the 125cc two-stroke power in general and not a Yamaha specifically. As I started the bike and began to warm it up, I immediately began to get excited. The memories of riding a 125cc two-stroke started to come back and I felt like I was 16 years old again. For Dirt Rider bike tests, we normally go out, ride for a few minutes to warm up, and begin looking for cool spots to shoot photos. After we’ve got all the shots we need, we then resume with testing. Halfway through our warm-up loop and my excitement level was continuing to build. It took a ton of willpower to not continue blasting around the trails for the sheer enjoyment of it. Instead, I headed back to the trucks to grab our photographer and begin shooting photos before continuing to ride and test.

2020 Yamaha YZ125X Engine

The YZ125X uses the same powerplant and gearbox as the YZ125—a Yamaha Power Valve System (YPVS)-equipped, 125cc, liquid-cooled, two-stroke, case-reed-valve-inducted engine that is paired to a six-speed transmission. It shares the same crankshaft, piston, clutch, intake, and exhaust system as the YZ125 as well. However, the YZ125X engine has been tuned for wide, smooth, and controllable power across the rpm range.

The YZ125X is a new model to Yamaha’s cross-country lineup for 2020.
The YZ125X is a new model to Yamaha’s cross-country lineup for 2020.Mike Vizer

Yamaha achieved this by changing the cylinder head and reducing the compression ratio. It altered the YPVS valve shape, effectively changing the exhaust port shape. It also increased the spring rate on the YPVS governor, allowing the power valve to remain closed slightly longer. Finally, the ignition timing was revised and optimized to match with the new compression ratio and exhaust port shape. The YZ125X has five degrees more ignition timing advance at low-to-mid rpm and is slightly delayed at high rpm.

It’s worth noting that the YZ125X is aggressively priced at $6,699 and the closest priced 125cc two-stroke competition model is the 2020 KTM 125 SX, which retails for $7,299.
It’s worth noting that the YZ125X is aggressively priced at $6,699 and the closest priced 125cc two-stroke competition model is the 2020 KTM 125 SX, which retails for $7,299.Mike Vizer

The first thing I think everyone will be asking is, How strong is the engine? And are the changes made to it relevant to cross-country racing? In my opinion, the engine is great and the changes to the cylinder head, ignition timing, YPVS spring, and exhaust port shape all did exactly what they were designed to do.

The engine runs clean, and for a 125cc two-stroke, it builds power well from the midrange all the way to very high rpm. While it is normal to shift gears more often on a 125cc two-stroke, with this engine and its six-speed close-ratio gearbox, the YZ125X required much less shifting than I expected. To help with low-end torque, Yamaha increased the rear sprocket size to a 50-tooth (up from the 48-tooth that comes on the YZ125). The 50-tooth rear sprocket meant first gear was low enough for technical sections and made second gear very useful in tight single-track. I found the gear spacing to be just about perfect and it was easy to find the right gear for nearly all situations.

While it is normal to have to shift gears more often on a 125cc two-stroke, the YZ125X required much less shifting than anticipated.
While it is normal to have to shift gears more often on a 125cc two-stroke, the YZ125X required much less shifting than anticipated.Mike Vizer

This engine is one of the smoothest 125s I have ever ridden. The gearing seemed to be paired just about perfectly with the powerband, making it even more fun to ride. Although we spent the majority of the day in slippery conditions, I made minimal adjustments to my riding to keep from spinning the rear tire.

There were some respectable hill climbs where we were able to really put the YZ125X to the test, and it passed with flying colors. For the most part, I used first gear and had zero issues. I attempted second gear on one of the longer hills, but found that once I lost a little momentum, I needed to downshift. The best part was how the YZ125X stayed on top of the dirt and did not dig a trench like some of the larger-displacement four-stroke bikes do. Even at the lowest of speeds and steepest of inclines, I was able to keep the bike moving forward without digging a hole like I was drilling for oil.

There were some respectable hill climbs where we were able to really put the YZ125X to the test and it passed with flying colors.
There were some respectable hill climbs where we were able to really put the YZ125X to the test and it passed with flying colors.Mike Vizer

Since the YZ125X is going to be used for cross-country racing and has a comparatively smaller-displacement engine, a strong clutch is going to be very important. I found the lever pull to be smooth and easy. Even in the tighter single-track when I was running second gear and abusing the clutch in lieu of downshifting, I experienced no fade.

2020 Yamaha YZ125X Suspension

The KYB suspension is set up very soft in stock trim, but offers plenty of adjustments to make it comfortable for a 160-pound intermediate and above rider.
The KYB suspension is set up very soft in stock trim, but offers plenty of adjustments to make it comfortable for a 160-pound intermediate and above rider.Mike Vizer

The YZ125X uses the same KYB Speed-Sensitive System (SSS) coil-spring fork and KYB shock as the YZ125. The spring rates remain the same between the two bikes with 4.1 N/mm fork springs and a 46 N/mm shock spring, but the components on the YZ125X have been revalved for cross-country racing.

The biggest adjustments I made were to the suspension. In stock form, it is very soft—certainly set up perfectly for a younger, lightweight rider stepping up from an 85cc or Super Mini bike or a 125-pound beginner up to almost a young intermediate rider. However, I am not saying it can’t be adjusted with the clickers to make it comfortable for a 160-pound intermediate and above rider. I simply went in a significant amount (there is plenty of room for adjustment) on all of the adjusters and found the suspension to perform quite well for faster-paced, fun trail riding. I made the following changes (stock settings are in parentheses):

Fork

Compression: 8 clicks out (12–15)

Rebound: 6 clicks out (11)

Shock

Low-speed compression: 8 clicks out (13)

High-speed compression: 1-5/8 turns out (1-5/8)

Rebound: 7 clicks out (12)

2020 Yamaha YZ125X Chassis/Handling

The YZ125X is an amazingly light-feeling motorcycle.
The YZ125X is an amazingly light-feeling motorcycle.Mike Vizer

The chassis on Yamaha’s two-stroke dirt bikes has not changed in several years, but it has been very good for a long time. The YZ125X shares the same chassis as the YZ125, including the bodywork and gas tank. Other notable features that come in stock trim include an 18-inch rear wheel with a rim size of 2.15 x 18, a D.I.D 520MXV5 O-ring chain, kickstand, and a reserve position on the fuel petcock so you don’t get stranded on the trail and can get back to the pits in case you run low on fuel.

With Yamaha’s tried-and-true chassis and its lightweight 125cc engine, the YZ125X is a very easy bike to ride. The one thing that truly amazed me is how light it feels. While it does not have the power of a 250F, it feels like the bike is 30 pounds lighter than one, and that makes a huge difference. Combine that with a very narrow chassis and in the tightest of single-track it felt like I was riding a mountain bike. The ease of bending this bike in between and around the trees was like wrapping a spaghetti noodle around a fork.

How Does The 2020 Yamaha YZ125X Ride?

The 2.1-gallon fuel tank is slightly small for longer cross-country races.
The 2.1-gallon fuel tank is slightly small for longer cross-country races.Mike Vizer

Overall, I had a blast on the YZ125X. It’s light feel and surprisingly torquey 125cc engine are a match made in heaven. I could ride this bike all day, stopping only when my 5-gallon gas jug was bone dry. This is a perfect bike to learn so many fundamental bike skills on without being intimidated by the weight and power of a 250F. I would feel much more confident having my kid spend a season on a YZ125X before going to a full-size competition 250F. While it’s perfect for the novice rider or one who is moving up from a minibike, it is not limited to that level. In the right hands, this bike can do almost everything a 250F is capable of and maybe some things a bit better as well.

Gearbox

In the right hands, the YZ125X can do almost everything a 250F is capable of and maybe some things a bit better as well.
In the right hands, the YZ125X can do almost everything a 250F is capable of and maybe some things a bit better as well.Mike Vizer

Helmet: 6D ATR-1

Jersey: FXR Racing Podium Air MX

Gloves: FXR Racing Slip-On Air MX

Pant: FXR Racing Podium Air MX

2020 Yamaha YZ125X Tech Spec

PRICE $6,699
ENGINE 125cc, liquid-cooled, single-cylinder two-stroke
TRANSMISSION/FINAL DRIVE 6-speed/chain
MEASURED HORSEPOWER N/A
MEASURED TORQUE N/A
FRAME Aluminum
FRONT SUSPENSION KYB Speed-Sensitive System (SSS) coil-spring fork adjustable for compression and rebound damping; 11.8-in. travel
REAR SUSPENSION KYB shock adjustable for spring preload, high-/low-speed compression damping, and rebound damping; 12.4-in. travel
FRONT BRAKE Nissin 2-piston caliper, 270mm disc
REAR BRAKE Nissin 1-piston caliper, 245mm disc
WHEELBASE 57.3 in.
SEAT HEIGHT 37.6 in.
FUEL CAPACITY 2.1 gal.
CLAIMED WEIGHT 209 lb. wet
AVAILABLE Now
CONTACT yamahamotorsports.com/motorcycle