2021 Yamaha YZ125X Specifications

Name: 2021 Yamaha YZ125X
Brand: Yamaha

Enduro / Off-Road • Specs last verified 13 July 2026

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2021 Yamaha YZ125X Overview

The 2021 Yamaha YZ125X is an enduro / off-road motorcycle built around 125 cc of displacement. Under the tank sits a Single cylinder, two-stroke engine, a compression ratio of 8.8:1. The bore and stroke measures 54 x 54.5 mm. From a practical standpoint, the 2021 YZ125X tips the scales at 94.8 kg, carries an 8-litre fuel tank, offers a seat height of 975 mm and spans a 1455 mm wheelbase. That's roughly 74.8 kg lighter than the average enduro / off-road motorcycle in our database. Scroll down for the complete 2021 Yamaha YZ125X spec sheet covering every technical detail from suspension travel to tyre sizes.

2021 Yamaha YZ125X compared with other bikes in the Enduro / Off-Road category

Here is how the 2021 Yamaha YZ125X stacks up against other bikes in the Enduro / Off-Road category in our database. Each model counts once, using the model year closest to this one, and the comparison covers up to 1434 models.

Seat height of 975 mm is taller than that of 1104 of the other 1145 bikes in the Enduro / Off-Road category.
Only 42 of the other 773 bikes in the Enduro / Off-Road category have a lighter wet weight than the 94.8 kg of the YZ125X.
With 125 cc, the YZ125X has the joint 191st smallest engine displacement of 1434 bikes in the Enduro / Off-Road category, 74% below the category average of 486 cc.
Narrowing the field to the 471 models within five model years of it, the seat height of 975 mm is taller than that of every one of the other 470.

Versus the 2020 model

The figures we track are unchanged from the 2020 model: wet weight, displacement and seat height all match.

2021 YZ125X - Pros & Cons

Strengths

Strong front braking: The single disc front brake gives excellent stopping power and responds well to aftermarket braided lines.

Considerations

Carburetor fuelling: Carbureted engines need occasional jetting attention and can be reluctant in cold weather or at altitude compared to modern fuel-injected alternatives.
Tall seat height: The 975 mm seat height will challenge shorter riders - tiptoeing at low speeds is something to factor into your decision.
Modest fuel capacity: The 8-litre tank means more frequent fuel stops on longer rides, which is worth planning around on touring routes.
Chain final drive upkeep: Chain final drive needs regular cleaning, lubrication and tension checks to get full life out of the sprockets.

Wear Points & Servicing Notes

Carburetor maintenance

The YZ125X uses carburetion rather than fuel injection, which means jetting is altitude- and temperature-sensitive and benefits from a clean-and-rejet after extended storage or an exhaust change.

Brake disc and pad wear

The single disc front brake gives strong, progressive stopping power. Disc thickness and pad depth are worth checking at every tyre change, since worn pads can score the disc surface.

Suspension condition on used examples

Up front, the YZ125X runs KYB® Speed-Sensitive System inverted fork; fully adjustable and KYB® single shock; fully adjustable at the rear. On a used example, check fork seals for weeping oil and test the rear linkage for play - seals are a relatively cheap fix but useful when negotiating price.

Final drive maintenance

Final drive is by chain - expect to clean and lube it every few hundred kilometres and check tension regularly; a neglected chain wears the sprockets faster than the chain itself.

Frame & chassis check

The frame is Semi-double cradle aluminium frame - worth a visual check for corrosion or impact damage around the head-stock and swingarm pivot on any used example, since frame damage is far costlier to fix than any service item.

Low-speed handling

At just 94.8 kg, the YZ125X is light enough to manhandle easily at a standstill - one of the practical advantages of its class.

YZ125X - Buying & Maintenance Guide

What to check before buying

When inspecting a used 2021 Yamaha YZ125X with its 125 cc enduro / off-road, start with the basics: check the service book for oil change frequency, inspect the drivetrain for wear, and look for oil seepage around the engine casings and rocker covers. This model runs chain final drive, so check chain slack and sprocket tooth profile specifically - a worn sprocket is a cheaper fix now than after it's chewed up the next chain. Now 5 years old, this enduro / off-road is as likely to show age-related wear (perished rubber, seized fasteners, degraded seals) as mileage-related wear. A cold start test is invaluable - a well-maintained YZ125X should fire up cleanly and settle to a smooth idle within a few seconds.

Oil and filter changes

Regular oil changes are the single most important maintenance task for the YZ125X's 125 cc single cylinder, two-stroke. Stick to the manufacturer's interval - typically every 6,000 km or once a year, whichever comes first. The sump holds 0.70 litres, so budget for that volume of quality motorcycle-specific engine oil. With an 8.8:1 compression ratio, running the octane grade specified in the manual matters more than on a lower-compression engine. Always use the correct viscosity grade as specified in the owner's manual.

Carburetor upkeep

Keep the carburetors clean and free of deposits. If the YZ125X has been stored, strip and clean the carb float bowls before attempting to start it. Pilot jets are the first to block and the last to be checked - always include them in any carb rebuild.

2021 Yamaha YZ125X - Frequently Asked Questions

What engine does the 2021 Yamaha YZ125X have?

The 2021 Yamaha YZ125X uses a Single cylinder, two-stroke engine with 125 cc of displacement.

How much does the 2021 Yamaha YZ125X weigh?

The 2021 Yamaha YZ125X weighs 94.8 kg. This is the manufacturer's wet figure.

What is the fuel tank capacity of the 2021 Yamaha YZ125X?

The 2021 Yamaha YZ125X has an 8-litre fuel tank. At around 5-6 litres per 100 km, that is roughly 133-160 km between stops.

Is the 2021 Yamaha YZ125X suitable for shorter riders?

The 2021 Yamaha YZ125X has a seat height of 975 mm. This is towards the tall end of the spectrum and will require most riders under 175 cm to tiptoe at stops.

What brakes does the 2021 Yamaha YZ125X have?

The 2021 Yamaha YZ125X uses single disc with hydraulic at the front and single disc with hydraulic at the rear.

What tyre sizes does the 2021 Yamaha YZ125X use?

The front tyre size on the 2021 Yamaha YZ125X is 90/90-21.

How much oil does the 2021 Yamaha YZ125X take?

The 2021 Yamaha YZ125X takes 0.70 litres of engine oil at a full oil and filter change. Always verify against the dipstick or sight glass after filling.

Yamaha YZ125X Spec Evolution

The Yamaha YZ125X was produced across 5 model years (2017-2023). The table below highlights the key specifications that changed across the production run - useful whether you are comparing years or tracking down a specific variant.

Specification	2017	2020	2021	2022	2023
Wet Weight	93.5 kg / 206.1 lbs	94.8 kg / 209.0 lbs	94.8 kg / 209.0 lbs	94.8 kg / 209.0 lbs	96.2 kg / 212.0 lbs
Seat Height	-	975 mm / 38.4 in.	975 mm / 38.4 in.	975 mm / 38.4 in.	970 mm / 38.2 in.
Fuel Capacity	8.00 litres / 2.11 gallons	8.00 litres / 2.11 US gallons	8.00 litres / 2.11 US gallons	8.00 litres / 2.11 US gallons	6.81 litres / 1.80 US gallons
Displacement (cc)	124.00 cc	125.0 cc	125.0 cc	125.0 cc	125.0 cc
Displacement (ci)	7.57 cubic inches	7.63 cubic inches	7.63 cubic inches	7.63 cubic inches	7.63 cubic inches
Oil Capacity (Quarts)	0.05 quarts	0.74 US quarts	0.74 US quarts	0.74 US quarts	0.74 US quarts
Frame Type	Semi-double cradle aluminium frame	Semi-double cradle aluminium frame	Semi-double cradle aluminium frame	Semi-double cradle aluminium frame	Semi-double cradle aluminium
Wheelbase	1,443 mm / 56.8 in.	1455 mm / 57.3 in.	1455 mm / 57.3 in.	1455 mm / 57.3 in.	1455 mm / 57.3 in.

Key Specifications

Engine

Single cylinder, two-stroke

Power

Not recorded

Torque

Not recorded

Top Speed

Not recorded

Weight

94.8 kg / 209.0 lbs

Fuel Capacity

8.00 litres / 2.11 US gallons

Full 2021 Yamaha YZ125X Specifications

Colours Team Yamaha Blue

Warranty 30 Day Limited Factory Warranty

Ground Clearance (in.) 13.8 inches

Ground Clearance (mm) 351 mm

Seat Height 975 mm / 38.4 in.

Wheelbase 1455 mm / 57.3 in.

Height 1285 mm / 50.6 in.

Length 2141 mm / 84.3 in.

Width 825 mm / 32.5 in.

Oil Capacity (l) 0.70 litres

Oil Capacity (Quarts) 0.74 US quarts

Fuel Capacity 8.00 litres / 2.11 US gallons

Wet Weight 94.8 kg / 209.0 lbs

Bore x Stroke (in,) 2.1 x 2.1 inches

Bore x Stroke (mm) 54.0 x 54.5 mm

Displacement (cc) 125.0 cc

Displacement (ci) 7.63 cubic inches

Engine Type Single cylinder, two-stroke

Engine Detail Reed-valve-inducted

Fuel System Carburettor. Mikuni TMX 38

Compression Ratio 8.8:1

Engine Lubrication Premix

Ignition CDI

Starter Kick

Clutch O-ring chain

Final Drive Chain (final drive)

Gearbox 6-speed

Frame Type Semi-double cradle aluminium frame

Suspension - Front KYB® Speed-Sensitive System inverted fork; fully adjustable

Suspension - Rear KYB® single shock; fully adjustable

Rake 26.8°

Trail 117 mm / 4.6 in.

Wheel Travel - Front 300 mm / 11.8 in.

Wheel Travel - Rear 315 mm / 12.4 in.

Brakes - Front Single disc. Hydraulic.

Brakes - Rear Single disc. Hydraulic.

Rims Dunlop® AT81 tires

Tyres - Front 90/90-21

Specifications are compiled from manufacturer documentation and cross-referenced technical sources, and corrected on an ongoing basis. Spot an error? Let us know.