At the heart of the 2021 Yamaha YZ125 cross - motocross motorcycle, Yamaha relies on a 125 cc (7.6 cu in) liquid-cooled single cylinder, two-stroke powerplant. Internal engine geometry specifies a bore and stroke of 54.0 x 54.5 mm (2.1 x 2.1 inches) with a 10.7:1 compression ratio.
On the scales, the YZ125 measures 93.9 kg (207 lbs) wet (curb). Rider ergonomics and chassis geometry center around a 975 mm (38.4 in) seat height — reflecting a long-travel chassis stance that favors ground clearance and off-pavement control, combined with a 1,443 mm (56.8 in) wheelbase engineered for balanced agility and highway composure. The 8-liter (2.1 US gal) fuel tank supports practical everyday commuting and weekend road stints.
Within MotoLibrary's Yamaha archive, this model family spans 19 indexed model years from 2008 to 2026, allowing buyers to track year-over-year changes in emissions tuning, weight and equipment.
Standover Height
975 mm (38.4 in)
Engine
Displacement125.0 ccm (7.63 cubic inches)
Engine TypeSingle cylinder, two-stroke
Engine DetailsReed-valve-inducted
Compression10.7:1
Bore x Stroke54.0 x 54.5 mm (2.1 x 2.1 inches)
Fuel SystemCarburettor. Mikuni TMX 38
IgnitionCDI
LubricationPremix
CoolingLiquid
Transmission
Gearbox6-speed
Final DriveChain (final drive)
ClutchMultiplate wet clutch
Chassis
Frame TypeSemi-double cradle aluminium frame
Rake26.0°
Trail109 mm (4.3 inches)
Front SuspensionKYB® Speed-Sensitive System inverted fork; fully adjustable
Front Travel300 mm (11.8 inches)
Rear SuspensionKYB® single shock; fully adjustable
Rear Travel315 mm (12.4 inches)
Wheelbase1443 mm (56.8 inches)
Ground Clearance366 mm (14.4 inches)
Wheels & Brakes
Front Tyre80/100-21
Rear Tyre100/90-19
Front BrakesSingle disc. Hydraulic.
Front Brake Ø270 mm (10.6 inches)
Rear BrakesSingle disc. Hydraulic.
Rear Brake Ø245 mm (9.6 inches)
WheelsDunlop® MX52 tires
Dimensions & Weight
Weight incl.93.9 kg (207.0 pounds)
Seat Height975 mm (38.4 inches) If adjustable, lowest setting.
Use this page to compare this motorcycle by its real specifications, not only by model name. Focus on the details that affect fit, comfort, handling, range and ownership.
Seat Height
Check the seat height against your inseam and riding posture before choosing a motorcycle.
Fuel Capacity
Fuel capacity helps estimate touring range and how often you may need to stop.
Brakes
Brake setup is worth comparing if you ride in traffic, mountains or with a passenger.
Suspension
Suspension details can matter for comfort, road feel and long-distance riding.
Transmission
Transmission and final drive affect maintenance, smoothness and everyday usability.
