Motorcycle specifications KTM125 SX 2027 His strength lies in his physicality

By switching to fuel injection, the 125 SX has changed its character but not its philosophy: to be an ultra-lightweight and highly efficient machine. Power is more readily available, smoother, and less dramatic for riders. It’s a machine designed for fun, without being too demanding, allowing riders to make the most of its strengths.

Performance

Designed to deliver torque, the 125 SX is ready to continue its dominance in its class with unrelenting momentum. The engine weighs just 17.86 kg and delivers impressive power. This lightweight engine retains its signature high-rev character while delivering power where it matters most.

Simplified suspension adjustment

As always, the suspension is easy to adjust tool-free at both ends, allowing riders to aim for the podium with complete control. At the rear, a dual hand-adjustable compression option lets riders fine-tune high- and low-speed settings in seconds. The front forks are also easily adjustable thanks to hand-adjustable ratchets on the bottom of the fork leg and on the top cap.

Electronic Fuel Injection System + Exhaust Valve Control

Handling is significantly improved thanks to the electronic fuel injection system. In addition to electronic fuel injection and a power valve on SX models, this delivers more usable power across the entire RPM range. This results in improved traction.

Electric start

Simply press the starter button to start the SX, thanks to a 12.8 V, 2 Ah lithium-ion battery located under the rider’s seat, a high-quality starter and power outlet, and a super-robust design.

Ease of maintenance

The SX line is designed to give riders easy access to replacement parts and suspension adjustment. This speeds up track-side and off-season maintenance and simplifies motocross for novice riders who don’t have a pit crew.

Selectable Map Settings

The 125 SX is designed to be at the cutting edge of technology in the 125cc class. It is equipped with a map selection switch that allows the rider to switch between maps. Mode 1, or White Map, delivers linear and predictable power, ideal for tackling dirty terrain with a leaner air-fuel mixture. Alternatively, Mode 2, or Green Map, is suited for sandy, loose, and deep conditions, with a richer mixture.

Total Control

The SX models feature revised frame updates, developed with the expertise of KTM Factory Racing. The area around the rear shock mount has been optimized, with engine mounts and cutouts that improve chassis flexibility. Up front, the frame features optimized wall thickness and updated engine mounts.

Ergonomics

The two-component plastic tank guards channel air to the radiators more efficiently, while a compact fuel tank roll allows for a tighter and more secure fit, reducing the risk of frame rubbing and significantly improving durability. All of this works in tandem with the rider triangle, which is specifically designed to provide unmatched grip and knee contact surfaces, particularly when standing on the footpegs.

WP XACT Fork

The 48mm WP XACT AER fork fitted to the SX models features a sealed air spring and a pressurized oil chamber for progressive and consistent damping, while oil and air bypasses reduce pressure spikes. Combined with the floating-piston damping system, it ensures excellent feedback and remarkable comfort. The fork also features adjustments that not only complement the frame and rear linkage but also guarantee exceptional performance across the board. It can be easily adjusted for preload using a simple air valve, as well as for compression and rebound via the easily accessible adjustment knobs. Additionally, the WP air pump required to adjust the fork pressure is included as standard in the buy-pack.

WP XACT Shock Absorber

At the rear, the WP XACT shock absorber uses settings directly derived from the KTM Factory Racing teams. The geometry of the frame and shock absorber provides greater ground clearance at the linkage, making it less prone to bottoming out. The small-diameter linkage bolts help save weight, while the new linkage seals improve rear shock response and advanced damping characteristics.

Stability

The KTM Motocross range is equipped with a special rear brake pedal that adds stiffness, flex resistance, and braking feel to the assembly. At the other end, a forged steering head and a CNC-machined fork crown ensure perfect alignment of the fork tubes. This precise geometry of the fork clamps ensures high responsiveness and smooth fork action, not to mention unwavering stability when riding through ruts and on the podium.

Tires

Dirt and performance rarely go hand in hand. However, hours of research and testing have led the KTM Motocross range to the Dunlop GEOMAX MX34. Offering unmatched stability and control at the highest level, the tire features a rigid casing and a rubber compound that improves damping and absorption, maintaining performance up to 30% longer than previous models. Progressive Cornering Block technology also improves grip in berms, while the rear tire features a wide, tall center block for desirable traction and control everywhere else. Finally, this unique block layout helps disperse mud buildup, ensuring traction even in very muddy conditions.

Energy Absorption

In addition to the hydroformed, laser-cut, and robot-welded frame—designed to provide exceptional rider feedback and straight-line stability—the chassis features specifically calculated longitudinal flex and torsion parameters. The frame thus acts as a shock absorber, resulting in a smoother ride and less fatigue over the course of the race.

Ground Clearance

No one enjoys unexpected crashes. Fortunately, the suspension geometry on the KTM SX and SX-F models provides ample ground clearance for the linkage, while the topography-optimized die-cast footpegs are less likely to snag in deep ruts or lift off in rough terrain.

Smoother Performance

Count on a durable chain guide and chain guard to minimize the risk of snagging on external objects, especially in extremely muddy conditions, while reducing dirt buildup around the swingarm and rear sprocket. Since 2026, the mounting points have been modified, and the cable routing is less prone to wear and damage.

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