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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 a 8-litre fuel tank, offers a seat height of 975 mm and spans a 1455 mm wheelbase. That's roughly 104 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 YZ125X - Pros & Cons
Strengths
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Factory engineering: The 2021 Yamaha YZ125X represents Yamaha's engineering at the time, with a specification built around real-world usability.
Considerations
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Carburetor fuelling: Carbureted engines need occasional jetting attention and can be reluctant in cold weather or at altitude compared to modern fuel-injected alternatives.
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Tall seat height: The 975 mm seat height will challenge shorter riders - tiptoeing at low speeds is something to factor into your decision.
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Modest fuel capacity: The 8-litre tank means more frequent fuel stops on longer rides, which is worth planning around on touring routes.
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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. Hydraulic. 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, start with the basics: check the service book for oil change frequency, inspect the chain and sprockets for wear, and look for oil seepage around the engine casings and rocker covers. 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 on any YZ125X. 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. 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 a 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. Hydraulic. at the front and Single disc. 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 |
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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 published by manufacturer
Torque
Not published by manufacturer
Top Speed
Not published by manufacturer
Weight
94.8 kg / 209.0 lbs
Fuel Capacity
8.00 litres / 2.11 US gallons
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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.
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