At Katoche, the 4-stroke cross country rhythm begins with the 250 SX-F. The 2020 version is once again called upon to take the ascendancy on the motocross tracks. Not content with being one of the lightest in its category, it offers unrivaled power deployment, but perfectly controllable. This is the reason why it appeals to both amateurs and professionals. The secret to a good engine is its ability to manage power with maximum efficiency. This package has serious assets in this area and will have no trouble leading you to victory.
Motor and muffler
The 4-stroke revolutionized motocross and allowed KTM to establish itself as one of the major players in this discipline. Incredibly light and compact, these little engineering gems impress with their power and dynamism. barely out of the dealership, the 4-stroke KTM allow you to experience the highest level, in the purest READY TO RACE spirit.
Renowned as one of the most powerful engines in the MX2 class, the 2020 version continues to consolidate its dominance. The compact architecture of the engine block allows better mass centralization and ensures impeccable road holding. The reliability of the 2020 model has further improved thanks to the various improvements made and the presence of a new, more robust oil pump intermediate gear. Powered by a compact, powerful and light engine (just 25.9 kg), the 250 SX-F is a force to be reckoned with. It is nonetheless easy to master, to the delight of amateur and professional pilots..
The centerpiece of the compact DOHC (double overhead cam) engine, the avant-garde cylinder head features two overhead camshafts responsible for actuating the titanium valves (32.5 mm intake, 26.5 mm exhaust) using ultra-light rockers coated with a DLC coating. The camshafts have an ultra-thin surface designed to minimize friction. The distribution has been studied to optimize the deployment of power.
The crankshaft of the 250 SX-F is particularly stiff. The big end bearing has two bush shells force-fitted directly into the crankpin. This type of design is essential to withstand the extremely high rotational speeds of the 250cc 4-stroke engine. It also makes it possible to increase engine life and to extend crankshaft maintenance intervals; a crucial advantage in terms of time, effort and costs.
Engine housings and covers
Using the high-pressure die-casting process results in a relatively compact and even lighter crankcase, while maintaining strength and durability. The design of the crankcase allowed KTM engineers to bring the shaft assemblies closer to the center of gravity, in order to better centralize the masses and enhance driving pleasure. Another interesting innovation to keep the engine as radiant as in its early days: engine crankcase covers with an elaborate surface structure, intended to reduce the wear caused by the rider’s boots.
The 250 SX-F has a robust 5-speed gearbox. The transmission ratios of the previous version, perfectly adapted to the practice of motocross, have been renewed. Another highlight of the transmission is the “zero dirt” design of the selector. Designed on the same principle as the footrest, it prevents the accumulation of dust and allows the gearbox to remain operational in all conditions.
The highly sophisticated Keihin engine management system with electronic fuel injection features a 44mm injection body. The position of the injector ensures excellent atomization of fuel and air entering the combustion chamber. The engine is all the more lively and generous when opening the throttle. You also have independent adjustment systems for cold start and idle. The control unit (ECU) offers maps specially adapted to the exhaust and the cylinder head, with the aim of better managing the traction control and the departure control. To deliver maximum power, it allows the characteristics of the engine to be adapted to each speed, according to the data communicated by the gear sensor engaged.
Cylinder and piston
The cylinder, with a bore of 78 mm, accommodates a forged piston of the bridge-box type of the highest quality, manufactured by CP. In addition to its extremely rigid structure, it stands out for its unique crown shape adapted to the high level of compression of the combustion chamber. The compression ratio (14.4: 1) and the reduced oscillating masses give the engine an extremely responsive character.
To compensate for the inertial force generated by the 250 SX-F, the engine is fitted with a multifunction balancer shaft. Besides its beneficial effect on the level of vibrations, the latter is also responsible for driving the timing chain and the water pump..
The DS (Diaphragm Steel) clutch transfers control to the rider. It consists of a durable one-piece clutch housing and main gear (made of heavy-duty steel billets), providing rock-solid reliability. It is fitted with extremely heat-resistant steel motor friction discs pre-stressed by a diaphragm spring, in order to optimize clutch release. This type of design has the effect of significantly reducing the force exerted on the clutch, which is even more true with the Brembo hydraulic system..
Every minute is precious in competition. The electric starter allows you to get back into the race without wasting time. The electric starter, available as standard on the 250 SX-F, uses the robust electric motor from MITSUBA. The foolproof reliability of this device saves precious start-up time at crucial points in the race.
Handlebar mapping selector
All 4-stroke models have a map selector·handy on the handlebars, which allows you to act on traction control and departure control and to switch between power curves (Standard Advanced). Traction control is intended to enhance traction and control of the motorcycle during acceleration phases, especially on demanding tracks. This function can be activated, even in full action, by means of the map selector·on the handlebars. When the engine is at idle, all you need to do is press both switches simultaneously to activate the start control as well, and thus leap out of the gate faster. In addition to the standard engine modes, the mapping selector provides access to other engine modes for maximum stroke options.
Maintaining optimum engine temperature is essential to ensure consistent power delivery. The position of the radiators of the 250 SX-F, perfectly adapted to the design of the spoilers, makes it possible to lower the center of gravity and improve ergonomics. Thanks to digital fluid mechanics (CFD) and the smart cooling system implemented, this innovative system ensures that engine components are kept at the ideal temperature to guarantee the highest level of performance, whatever the conditions. The special protections with which the radiators are fitted not only serve to protect them from projections of stones and other debris, but also to distribute the impact force of the shock around the radiators.
The exhaust system, provided on all 4-stroke models, gives the engine a smoothness and liveliness difficult to match. It has an exhaust manifold (specific to each model) and a small additional chamber, that is to say an evolved resonator called FDH (Flow Design Header) or flow-design exhaust manifold. This design allows the exhaust to be removed without having to remove the shock absorber and facilitates access to the shock absorber. Another advantage from the point of view of ergonomics is the aluminum sleeve, the silencer tip and the internal structure of the silencer, as they refine the silhouette of the motorcycle while respecting the regulatory noise emission levels..
The better the sensations on the bike, the more the adventure is likely to be beautiful and intense. The chassis plays a key role in terms of road feel. The 250 SX-F relies on a lightweight high-tech steel frame capable not only of mitigating the effects of the many irregularities in motocross terrain, but also of providing excellent feedback to the rider. The damping characteristics of the suspensions have been optimized on the 2020 version. The suspension settings have in particular been revised to provide additional flexibility and comfort. Combined with a flexible chassis, these suspensions make the driving experience more intuitive and pleasant than ever..
The 250 SX-F’s frame favors the dynamic riding styles that are standard in the class. As with the rest of the KTM SX range, the frame is made from hydroformed chrome-molybdenum steel tubes, assembled by automated welding, to ensure the highest levels of quality. The rigidity has been studied to enhance handling. The excellent cohesion with the suspensions also offers the perfect compromise between agility and stability at high speed. The frame of all 2020 KTM SX models benefits from a heavy-duty lacquer coating and standard frame protectors. The rear buckle, made of lightweight aluminum, offers an excellent feeling to the rider and promotes mobility in the saddle.
The 250 SX-F’s one-piece swingarm, obtained by high-pressure die-casting, was engineered to offer heavy-duty strength at minimal weight. It allows a wide range of adjustments at the rear wheel and makes it possible to reduce the wheelbase to increase handling on narrow, winding tracks or, on the contrary, to increase the wheelbase to promote stability on fast sections. The chain measurement marks shown on the swingarm are visible from above, which greatly facilitates adjustments.
Equipped with ultra-light CNC machined hubs and premium Excel rims, the wheels of all SX models guarantee maximum stability despite a limited weight. The aluminum spoke nipples have been revised to limit the frequency at which it is necessary to retighten the spokes. The wheels are shod with latest generation DUNLOP Geomax MX 3S tires, to maximize power transfer to the ground and gain stability.
All full-size KTM SX models feature the ultra-light WP XACT AER fork, which has new settings on the 2020 vintage. The arms of this 48mm USD air fork have a different function: damping is on the right, the air spring is on the left. The left fork leg has a dual chamber and air cartridge system to prevent pressure loss. Should the outer seal ever leak, the pressure exerted inside the inner cartridge will keep the motorcycle in its normal position. The extremely easy to adjust air spring can be adjusted to the weight of the rider using a single valve and the air pump supplied with the motorcycle. The right fork leg features a cartridge specifically designed to meet the demands of the single damper 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), all you have to do is turn the new 30-notch dial provided for this purpose above each fork leg..
The WP XACT DDC shock absorber, present on all KTM SX models, has been developed taking into account the architecture of the frame and the swingarm, just like the linkage system and the WP XACT AER fork. Beyond its purely functional aspect, this little gem seduces by the care taken in the finishes, and in particular by its high quality machined and anodized components. Fully configurable in high-speed and low-speed compression, it can be adapted specifically to track conditions or pilot preferences.
All KTM SX models use high quality CNC machined triple trees, a trademark of KTM. To account for the flexibility of the frame and fork, engineers have firmed up the upper triple tree (22mm offset on all models). The front axle, working in perfect harmony with the frame, makes the bike even more stable and agile. Two positions are possible for the handlebar trigger guard with shock absorbing pads intended to attenuate vibrations. Hour meter, fitted as standard on the upper triple clamp of all SX models, tracks hours spent in the saddle and indicates when it’s time for service.
State-of-the-art Brembo brakes are standard equipment on KTM motocross bikes. Combined with Wave brake discs renowned for their lightness, they provide the braking power expected by the most daring riders.
All models in the KTM SX range have an ultra-light polyethylene fuel tank. The shape of this tank has been designed to be more ergonomic, while maintaining the same capacity (7 liters). Fuel tank cap with internal thread ensures easy and reliable closing.
Air filter housing
The 250 SX-F’s air filter housing has been completely redesigned to optimize flow dynamics. Associated with the new intake snorkels, it ensures an exceptional power deployment and level of acceleration. In addition to the obvious performance gain, the new design also serves to better protect the air filter against soiling. The rigid support for the large Twin-Air air filter has been designed to minimize installation errors. As on previous models, filter maintenance is carried out in record time and without tools, an original feature, typically KTM.
Ergonomics and comfort
The stronger the cohesion with his motorcycle, the more the rider will be able to move spontaneously and naturally and maintain good dynamics on his motorcycle. To offer flawless ergonomics and guarantee an optimal level of performance on the 2020 range, KTM engineers have ensured that the rider can adopt an ideal position on his motorcycle, in order to gain in handling. It is also possible to adjust the position of the handlebars according to the preferences and size of the pilot. As the rider primarily interacts with the fairing, saddle, footrests and handlebars, these contact points are critical to maintaining full control of the vehicle. KTM did not want to compromise on ergonomics and has consistently opted for the best quality components on the 2020 KTM SX models..
The saddle of all KTM SX models confirms the progress made in terms of dynamism and ergonomics. The saddle cover incorporates silicone bands designed to optimize grip and feel. A long screw inserted on the side allows the saddle to be better fixed to the motorcycle and makes its handling easier and safer.
All full-size KTM SX models feature the same super strong aluminum profile handlebars, manufactured by NEKEN. Two positions are possible for the handlebar trigger guard with shock absorber pads. right: an ODI vulcanized handle available as standard; on the left: an ODI lock-on handle as comfortable as it is practical, thanks to its mounting system without glue or wire.
Sophisticated ‘zero dirt’ footrests prevent soiling of the pivot, even when going through deep ruts. The driving position is not high enough? Never mind ! The footrest mounting system of EXC models from model year 2019 has been increased by 6 mm compared to that of SX versions.
Dressing and graphics
KTM 4-stroke motocrosses are the market benchmark for innovation and style. The result of collective work between KTM factory pilots, R specialists&D KTM and the design agency Kiska GmbH, the fairing of the 250 SX-F marks a new stage in the evolution of motorcycles, both stylistically and functionally. The shape of the fairing allows the pilot to truly become one with his machine. The work mainly focused on the contact points to guarantee full freedom of movement for the pilot and increase handling. The particular shape of the front and rear shells ensures maximum stability, for minimum weight.
The new overmolded graphic kit reinforces the aggressive look of the motorcycle and confirms the ambitions of the KTM brand.
Software and electronics
The 4 strokes were a turning point in the motocross era. The SX-F range of motorcycles have enabled KTM to push the boundaries of performance innovation. To stay ahead of its rivals in the MX2 class, KTM equipped the 250 SX-F with a mapping selector·on the handlebars. This activates innovative functions such as traction control and departure control and even allows the power curve to be changed. An absolute level of performance demands state-of-the-art electronics to transfer maximum power to the ground. KTM SX-F models also benefit from unique advantages such as the proven electric starter. Now you can switch to READY TO RACE mode at the touch of a button.
To start the engine every time, especially in cold weather, the starter motor on the SX-F models is powered by an ultra-light, high-performance 2 Ah lithium-ion battery. The voltage regulator and capacitor, as well as all electrical components, have been brought together under the saddle, for the sake of reliability and compactness.
This function, extremely practical in use, guarantees more efficient traction and better control of the motorcycle when accelerating on wet or slippery surfaces. It can be activated, even in full action, by means of the map selector·on the handlebars.
It suffices to press simultaneously on the two map selector switches to activate the START CONTROL and thus jump out of the starting gate more quickly. Start Control reduces the maximum engine speed at the exact moment you are going off so you can maintain better control of your machine. The EFI light mounted on the upper triple clamps flashes when this function is active.
Handlebar mapping selector
The mapping selector allows, with the push of a button, to switch between a standard engine mode and a more aggressive engine mode on trails with good grip. This allows the rider to better adapt the ride of the motorcycle to the track conditions or to benefit from better control when he begins to show signs of fatigue..
Info and image credits: KTM
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250 SX-F 2019
Model marketed in
The technical aspect
2020 KTM 250 SX-F
- Tank: 7 liters
- Dry weight: 99 kg
- Train before
- secondary by chain
- Rear axle
(78 x 52.3 mm)