Motorcycle specifications KTM125 SX 2020 The first explanations

The KTM 125 SX is a delight to ride. It is one of the most compact and lightest of the standard-sized motorcycles. The combination of a lighter chassis and one of the most powerful 125 cm3 2-stroke engines in its class opens up new horizons for the most impetuous of young riders. More lively than ever, this 2-stroke allows you to get your teeth into it and fill up your trophy collection before entering the profession.

engine

the 125 SX engine is once again the most powerful and competitive unit in its class. Its excellent power-to-weight ratio, low cost and simplicity prove that 2-stroke technology has a bright future at KTM. This compact, durable 17.2 kg engine, the fruit of KTM's technical expertise, delivers great power across the entire rpm range. Precise and powerful, this engine delivers excellent lap times and better results.

cylinder

the cylinder, with a bore of 54 mm, has been the subject of several improvements within the 125 cm3 engine. It features an optimized control spindle and a sophisticated mechanism for the side support exhaust channels. The new configuration of the exhaust channels contributes to increasing the engine's performance level. The upper contour of these components has even been machined to ensure ultra-precise timing. Combined with the two-piece cylinder head, this reworked cylinder is responsible for a clear increase in power across the 125 SX's rev range.

crankcases and covers

the use of a high-pressure molding process produces thin walls while preserving the strength and durability of the crankcase. The crankcase design enabled KTM engineers to raise the position of the crankshaft closer to the center of gravity, thus centralizing mass and enhancing rideability. The lightness of the engine block owes much to the extremely compact shape of the crankcase. The intermediate kick pinion on 2020 models has been redesigned for greater reliability.

gearbox

the 125 SX features a robust 6-speed gearbox. The transmission ratios of the previous version have been retained, but the sprockets have been improved and reinforced. For added security, the gearbox features a new balance shaft that holds the front sprocket in place with a bolt and diaphragm spring instead of a snap ring. Another transmission highlight on the 125 SX is the "zero dirt" design of the selector. Designed on the same principle as the footrest, it prevents the accumulation of dust and enables the gearbox to remain operational in all conditions.

carburetor

the 125 SX features a MIKUNI TMX 38 mm flat-barrel carburetor with settings adapted to the new air filter box introduced in 2019. The valve gearboxes of the 2020 models have undergone a number of functional and technical improvements (improved sealing and reliability) to ensure linear power delivery throughout the rev range.

contact

all 2-stroke models feature a CDI gearbox and advanced components designed to improve engine starting behavior. Ignition curves remain unchanged.

cooling

to ensure smooth power delivery, it's essential to maintain optimum engine temperature. To this end, the 125 SX can count on new radiators that are 12 mm lower than those of its predecessor. This position, perfectly matched to the design of the new spoilers, lowers the center of gravity and enhances ergonomics. Thanks to CFD (Computational Fluid Dynamics) and a clever cooling circuit, this innovative system ensures that engine components are kept at the ideal temperature to guarantee the highest level of performance, whatever the conditions. Special radiator guards not only protect the radiators from stones and other debris, but also distribute the force of impact around them.

muffler

the exhaust system, specially developed for this bike, gives the engine a smoothness and liveliness that are hard to match. Its special shape provides a real plus in terms of ergonomics, while respecting the noise emission levels recommended for racing.

chassis

so that you can fully enjoy the exhilarating driving experience of a 125 cm3 2-stroke, KTM has developed a chassis to match your ambitions. The high-tech steel frame not only reacts instantly to the rider's inputs, but also provides excellent feedback. Its flexibility has been specially designed to absorb the heaviest shocks and enhance the bike's agility and stability at high speeds. Suspension damping characteristics have been optimized on the 2020 version. In particular, suspension settings have been revised to provide extra suppleness and comfort, allowing the rider to remain in complete control of the bike.

frame

the 125 SX's frame and rear buckle encourage the aggressive riding styles that are de rigueur in the 125cc class. The frame is made of hydroformed chromium-molybdenum steel tubes, assembled by automated welding to guarantee the highest levels of quality. Rigidity has been specially designed to guarantee unrivalled manoeuvrability. The excellent cohesion with the suspension offers the perfect compromise between agility and high-speed stability. And with self-cleaning "zero-dirt" footrests that won't jam when returned to position, you're in complete control, whatever the conditions. The frame of all SX models inherits the highly resistant lacquer coating (used on KTM Factory machines) and standard frame protectors. The rear buckle, made of lightweight aluminum, reinforces the stability of the rear shell and provides excellent support for the rider, despite its low weight.

swingarm

the one-piece, high-pressure-molded swingarm has been designed for maximum strength and minimum weight. It offers a wide range of rear-wheel adjustments, allowing you to reduce the wheelbase for greater manoeuvrability on narrow, winding tracks, or increase it for greater stability on fast sections. The chain measurement marks on the swingarm are visible from above, making adjustments much easier.

wheels

featuring ultra-light CNC-machined hubs and top-of-the-range Excel rims, the wheels on all SX models guarantee maximum stability despite limited weight. The aluminum spoke nipples have been redesigned to reduce the frequency with which spokes need to be re-tensioned. The wheels are fitted with latest-generation DUNLOP Geomax MX 3S tires, to maximize power transfer to the ground and enhance stability.

front suspension

all standard-size KTM SX models feature the ultra-light WP XACT AER fork. The arms of this 48 mm USD air fork have different functions: damping is on the right, air springing is on the left. The left fork arm features a double-chamber air cartridge system designed to prevent any loss of pressure. Should the outer seal leak, the pressure exerted inside the inner cartridge will keep the bike in its normal position. The air spring is extremely easy to adjust, and can be adapted to the rider's weight using a single valve and the air pump supplied with the bike. The right fork arm features a cartridge specially designed to meet the requirements of the single-arm design, and can be adjusted to suit track conditions or rider preference. To fine-tune each of these settings (compression from the top and rebound from the bottom), simply turn the new 30-notch knob above each fork arm.

rear suspension

the WP XACT DDC shock absorber, featured on all KTM SX models, has beenthe WP XACT DDC shock absorber, found on all KTM SX models, was developed with the frame and swingarm architecture in mind, as were the linkage system and the WP XACT AER fork. Beyond its purely functional aspect, this little jewel captivates with its meticulous attention to detail, and in particular its high-quality machined and anodized components. Fully adjustable for high-speed and low-speed compression, it can be specifically adapted to track conditions or rider preferences.

fork tees

all KTM SX models use high-quality CNC-machined fork crowns, a KTM trademark. To take account of the flexibility of the frame and fork, engineers have stiffened the upper fork crown (22 mm offset on all models). The front end works in perfect harmony with the frame, making the bike even more stable and agile. Two positions are possible for the handlebar trigger guard, with vibration-damping rubber. The hour meter, fitted as standard on the upper fork crown of all SX models, keeps track of hours spent in the saddle and indicates when it's time for maintenance.

brakes

state-of-the-art Brembo brakes are standard equipment on KTM motocross bikes. Combined with Wave brake discs renowned for their lightness, they deliver the stopping power expected by the most daring riders.

fuel tank

all KTM SX models feature an ultra-light polyethylene fuel tank. The shape of this tank has been designed to be more ergonomic, while retaining the same capacity (7 liters). The internally threaded fuel filler cap ensures easy, reliable closure.

air filter housing

the air filter housing on the 125 SX optimizes flow dynamics. Combined with the intake snorkels, it ensures maximum power delivery and excellent acceleration. In addition to the obvious performance gains, the design also protects the air filter from clogging. The rigid support for the large Twin-Air filter has been designed to minimize installation errors. As on previous models, the filter can be serviced in record time and without tools, a typically KTM feature.

ergonomics and comfort

maintaining a good dynamic is essential for good lap times on a 125 cm3. To maintain an excellent pace, it's crucial to be able to move around the bike quickly and easily, and to be at one with it. To ensure flawless ergonomics and optimum performance, KTM engineers have made sure that the rider can adjust the position of the handlebars (according to preference and conditions) and adopt an ideal posture on the bike. How the rider interacts with the fairing, saddle, footpegs and handlebars has a direct impact on finding the balance point and mastering the bike. Since there was no room for compromise in these areas, KTM set out to select the very best, both in terms of product quality and design. The 125 SX 2020 instinctively gives the rider the impression of being in complete control of the situation. This feeling is confirmed from the very first turns of the wheel.

saddle

the saddle on all KTM SX models confirms the progress made in terms of dynamism and ergonomics. The saddle cover incorporates silicone strips to optimize grip and feel. A long screw inserted into the side of the saddle secures it more securely to the motorcycle, making it easier and safer to handle.

handlebars

all standard-size KTM SX models feature the same ultra-strong, profiled aluminum handlebars made by NEKEN. Two positions are possible for the handlebar trigger guard with shock absorbers. right: an ODI vulcanized handlebar grip available as standard; left: an ODI lock-on handlebar grip that's as comfortable as it is practical, thanks to its glue- and wire-free mounting system. The handlebars feature handlebar foam and handguards that are easy to fit and remove.

footrests

sophisticated "zero-dirt" footrests prevent the gear selector from getting dirty, even when riding in deep ruts.

software and electronics

the 125 SX boasts electronics to match its ambitions. Pure 2-stroke simplicity, the hour meter (available as standard) keeps track of hours spent in the saddle, while the tachometer (available as an option) helps you find the ideal rpm.

Information and images credits: KTM