125 SX - 2020


125 SX - 2020 Promotions

Model Description

The KTM 125 SX is the most compact and lightweight of the full-size bikes and delivers a confidence-inspiring ride like no other. A lightweight chassis teams up with the most competitive 125cc 2-stroke engine in its class, delivering superior agility and power to fulfil the demands of any young adrenaline seeker. This 2-stroke screamer is the ultimate entry point into the pro ranks and a sure-fire way to add to the trophy collection.
The bike's tried and tested crankshaft has a stroke of 54.5 mm featuring an excellent balancing which reduces vibrations to a minimum. It is possible to increase the displacement of the latest engine generation to 144cc by a replacing the cylinder, piston and cylinder head without changing the crankshaft. 
At the core of the engine is a compact cylinder with a 54 mm bore. It features an innovative power valve unit with a sophisticated mechanism designed for the lateral support exhaust ports. The exhaust port layout enhances engine performance, while the precise machining of the upper contour of the exhaust port ensures accurate port timing. Together with a twin-component cylinder head, this has resulted in outstanding engine performance and throughout the entire rpm range.
The header of the KTM 125 SX using the latest 3D stamping technology has been given an optimal shape and, in conjunction with the silencer internals, results in a fat torque curve and strong power delivery.

The lightweight DS (diaphragm steel) clutch features a one-piece outer clutch hub combined with a primary gear made of high strength billet steel. This guarantees unbeatable reliability and is extremely compact. Incorporating thin steel carrier friction discs, the extremely heat-resistant clutch plates ensure reliable disengagement of the clutch. An additional benefit is that they are pre-tensioned by means of a specially designed diaphragm spring, which significantly reduces the force required to pull the clutch lever. The Brembo hydraulic system also ensures an easy and precise action.

The robust 6-speed transmission unit in the KTM 125 SX comes from a transmission plant operated by Pankl in Austria which represents the best there is in terms of quality and reliability. KTM's advanced No-Dirt technology is used for the gear shift lever and is designed to prevent mud and dirt from fouling the lever joint and thus guarantees reliable gear changing at all times.

It is common knowledge that the KTM 125 SX engine is the most powerful and most competitive engine in its class. KTM is absolutely convinced that 2-stroke technology, with its outstanding power-to-weight ratio, low costs and uncomplicated engineering, will continue to lead the chase in the future. The 125cc engine was developed using the most advanced engineering expertise KTM has to offer and is the most powerful in this segment over the entire rpm range. Weighing in at a mere 17.2 kg, it is the lightest engine in its class. This gives the rider precisely what he wants – faster lap times as a result of the bike's handling and outstanding overall performance.

The crankshaft of the KTM 125 SX is positioned high up in the die-cast crankcase at a point that is now closer to the center of gravity. This contributes to improved centralization of the masses and at the same time optimizes rideability. The engine unit is extremely compact and is a major factor in keeping down the overall weight of the bike.

The KTM 125 SX is fitted with a 38 mm flat slide MIKUNI carburetor, which provides a smooth and controllable power delivery over the entire rpm range and offers tremendously precise throttle response.

Model Specification


Engine Type

Single cylinder, 2-stroke


124.8 cc




6 gears


Wet multi-disc clutch, Brembo hydraulics



Central double-cradle type


5/8 x 1/4

Steering Head Angle

63.9 degrees

Tank Capacity

7.5 litres


Brake System Front

Disc brake 260 mm

Brake System Rear

Disc brake 220 mm


Front Suspension

XACT WP upside-down fork, 48 mm

Rear Suspension

XACT WP shock absorber with linkage

Suspension Travel Front

310 mm

Suspension Travel Rear

300 mm



54 mm


54.5 mm

Ground Clearance (unloaded)

375 mm

Seat Height

950 mm

Weight (No Fuel)

87.5 kg


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