The KTM 125 SX is the most compact and lightweight of the full-sized KTM motocross arsenal, delivering championship-winning performance to up-and-coming racers. Due to its confidence-inspiring performance, lightweight chassis and overall agility, the KTM 125 SX has become the most competitive 125 cc 2-Stroke engine in its class. For 2022, 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 2022 KTM 125 SX undoubtedly boasts the most competitive and powerful engine in its class. With an outstanding power-to-weight ratio, low cost, and overall simplicity, it is clear that this 17.2 kilogram, 2-stroke mill will continue to have a successful future in KTM motorsports.
At the heart of the 125 cc engine is a cylinder with a 54 mm bore. It features a powervalve unit with a sophisticated mechanism designed for the lateral support exhaust ports. The exhaust port layout enhances engine performance, while the upper contour of the exhaust port is machined to ensure more accurate port timing. Together with the two-component cylinder head, this key to the KTM 125 SX's outstanding performance across the entire rev range.
Crankcases and engine covers
The lightweight engine cases are manufactured using a high pressure die-cast production process, keeping wall thickness to a minimum while retaining strength and durability. The design allows for a high crankshaft position which is located near to the center of gravity, resulting in optimal mass centralization and easier rideability. The engine body is extremely compact, which contributes significantly to the low engine weight.
The KTM 125 SX is fitted with a robust 6-speed transmission. The gear ratios, which featured improvements and reinforcements, were carried over from its predecessor. Another highlight of the 125 SX transmission is the "no-dirt" gear shifter. Similar to the footpeg design, it prevents the build-up of dirt and ensures the next gear is always available, no matter what the conditions.
Getting the fuel to the cylinder comes courtesy of a MIKUNI TMX carburetor. The settings on the 38 mm flat slide carburetor perfectly suit the airbox and exhaust design, providing smooth, controllable power all the way through the rev range.
All KTM 2-stroke motocross models feature a CDI control unit with advanced hardware that improves the starting behavior of the engine. This means they fire perfectly everytime, all the time.
Keeping things cool when the going gets heated, is a set of radiators ideally positioned for a lower center of gravity. By using computational fluid dynamics technology together with a clever coolant circuit routing, the innovative system ensures the optimum engine temperature for the highest performance, no matter what the conditions.
Their's more to it than 'braaaap!'. The exhaust plays a key role in packing that signature 2-stroke punch. When it comes to power delivery and performance, the exhaust is developed specifically for the KTM 125 SX and plays a key role packing a punch. In addition, its special shape provides slimmer ergonomics while still operating safely within the noise limits for racing.
The KTM 125 SX makes use of a pin-point accurate hydro-formed chromium-molybdenum frame. These are robot welded to ensure the highest levels of consistent quality, stiffness, and responsive handling. And when paired with the WP PRO COMPONENT suspension, provides excellent agility and high-speed stability. For 2022, all KTM SX frames are powder-coated in full-factory orange and come with standard frame protectors. The subframe is made from lightweight aluminum and provides a great feeling for the rider, as well as easy movement across the seat.
The KTM SX range features a one-piece, gravity die-cast swingarm. This manufacturing process ensures exceptional strength at the lowest possible weight, and offers a wide range of adjustment for the rear wheel, allowing for a shorter wheelbase on tighter, twisty tracks, or a longer wheelbase for greater stability on longer straightaways. Additionally, the swingarm's chain measurement markings are visible from above, meaning adjustments are easily made.
The full-size KTM SX machines make use of lightweight, CNC-machined hubs and high-end Excel rims, wrapped in the latest Dunlop Geomax-MX33 tires. The aluminum spoke nipples feature a design that conveniently reduces the frequency with which the spokes need to be tightened.
The KTM 125 SX makes use of lightweight 48 mm USD WP XACT front forks with AER technology. These air-sprung forks feature separate functions in each fork leg, with damping functions on the right side and the air spring on the left. The left leg features a two-chamber system with a capsuled air cartridge, preventing loss of air pressure. Essentially, this means that in the rare case of a leaking outer seal, the internal cartridge pressure maintains its standard position. The air spring is also easy to use and can be adjusted to any rider weight via a single air valve and an air pump which is supplied. The right fork leg integrates a damping cartridge to fit single damping leg requirements and can be adjusted to track conditions or rider preferences. Additionally, the fork top caps feature easy adjustment, with compression done from the top, and rebound from the bottom.
All KTM SX models make use of a WP XACT mono-shock, which has been developed to work with the entire frame and swingarm architecture, as well as the linkage system. This setup perfectly compliments the WP XACT fork, to provide balance and handling performance. It features high-quality machined and anodized components, is fully adjustable, including high and low-speed compression, and allows you to set the shock up precisely to suit any track and rider's preferences.
High-quality, CNC-machined triple clamps have become a KTM trademark. With a precisely calculated stiffness and 22 mm offset, these have been developed to match the flex characteristics of the frame and fork, resulting in unbeatable handling and stability. An hour meter is fitted as standard on the upper triple clamp on all SX models, keeping the rider informed of the number of hours spent tearing up the track and when the next service is due.
The KTM SX range relies on the best in the business when it comes to slowing down. High-tech Brembo brakes take charge of the front and rear, ensuring maximum rider feel, less brake fade, and high-quality build quality. Combined with lightweight wavey discs, this race-proven system provides the highest level of braking efficiency, providing unrivaled stopping power.
Feeding the high-revving machine beneath, a lightweight, 7-liter polyethylene fuel tank ensures an uninterrupted flow of fuel at all times. The shape of the fuel tank also aids in the overall, slim ergonomics of the bike, without compromising on fuel capacity.
The airbox on the KTM 125 SX ensures optimal flow dynamics, and together with its intake snorkels, leads to maximum power and quick throttle response. Despite the obvious performance advantages, the design also offers maximum protection against soiling of the air filter. The large Twin-Air air filter is mounted on a cleverly designed stiff cage that minimizes incorrect installation. As found on previous models, filter maintenance is quick and easy and does not require tools - a standard, original feature from KTM.
All KTM SX models feature a seat that merges dynamic performance-oriented ergonomics, and grip, thanks to laterally spaced silicone strips. Seat removal is also an easy affair, thanks to one long, lateral screw, making it secure and easy to handle. For 2022, the seat receives a factory-inspired blue color.
All full-size KTM SX models are equipped with the same high-strength aluminum tapered handlebar, made by NEKEN. The handlebar is fixed in rubber damped mountings, which allow for two different positions. The handlebars come standard with an ODI vulcanized grip on the right side and a comfortable ODI lock-on grip, which does not require any wire or glue, on the left. They also feature a bar-pad with a cover that can be attached and removed with little effort.
Sophisticated self-cleaning ´no-dirt´ footpegs prevent mud clogging up the pivot, even when digging in deep ruts. This means you maintain perfect grip at all times. One less thing to worry about then you're leading a chasing pack.
In an ode to KTM's illustrious past in the motocross realm, the KTM 2022 SX range receives a nostalgic makeover, merging distinctive Red Bull KTM Factory Racing colors with old-school inspired design. A new blue seat and orange frame complete this visually striking package.
1-cylinder, 2-stroke engine
Bore X Stroke
54 mm x 54.5 mm
Fuel Tank Capacity
Brakes Type Front
Disc brake 260 mm
Brakes Type Rear
Disc brake 220 mm