- What you must remember
- Make your2018 KTM 250 SX
- The technical aspect
- Related articles
In the world of motocross, the KTM 250 SX boasts one of the best power-to-weight ratios in its class. Sure of its strength, it is even ready to do battle with more complex 4-stroke motorcycles. With the punch to excel on any type of circuit and terrain and an unusual sense of placement thanks to its ultra-light chassis, the jewel of KTM’s R&D teams and motorsport specialists is set to become the future. king of discipline.
The 2-stroke engine of the KTM 250 SX has long had a reputation as the most powerful block in its class and confirmed the enormous potential of 2-stroke engines at KTM. Inexpensive, these engines stand out for their simplicity. And what about their weight / power ratio? It is simply mind boggling. The engine of the KTM 250 SX has benefited from many improvements: better mass centralization, control axis managed by a TVC exhaust valve, balance shaft to reduce vibrations, 5-speed gearbox and hydraulic DDS clutch. Quick as lightning, this compact engine has everything to dazzle competitors in search of performance and seduce pilots attentive to their budget and maintenance costs. Let yourself be stunned by that sweet roar characteristic of a 2-stroke engine.
This ultra-compact cylinder, with a bore of 66.4mm, features a state-of-the-art drive shaft and a sophisticated mechanism for the side carrier exhaust channels. Combined with the two-piece cylinder head, this design is the source of a marked increase in power throughout the range. The arrangement of the water jackets inside the cylinder and the cylinder head allows efficient heat dissipation under heavy load on the engine.
The die-cast crankcases have been designed to free up room to fit a balance shaft, so you can whip up the miles at top speed and relaxed. 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.
Numb hands or feet are not inevitable. The design of the engine made possible the use of a lateral balance shaft which helps to minimize vibrations. This obviously has a beneficial effect on driving pleasure..
The robust gearbox offers 5 ratios perfectly suited to the range of use of the 250. The “zero dirt” design of the selector avoids soiling and blocking of the lever articulation for safer gear changes.
The KTM 250 SX uses a DDS (Damped Diaphragm Steel) clutch developed by KTM; It features a sturdy steel clutch housing, high heat resistance clutch discs and new nitrate treated steel liners that are less prone to wear. This judicious design is distinguished by the use of a diaphragm spring in place of the usual coil springs, giving the clutch greater flexibility. The diaphragm spring also leaves enough room for a damping system integrated into the clutch hub, in order to promote traction and durability. The clutch is activated by a hydraulic system manufactured by Brembo, which plays an essential role in the progressiveness and flexibility of the clutch..
Attention has been paid to the resonator to deliver even more power and torque. This engine is a marvel of explosiveness and solidity.
All 2-cycle models feature a new condenser-discharge ignition control unit and advanced components to improve engine start-up behavior. The ignition curves have not changed.
The KTM 250 SX is fitted with a MIKUNI TMX carburetor. This 38mm flat bushel carburetor allows a clear improvement and a better dosage of power up to the rev limiter. Thanks to a new distributor tube, the carburetor has been rotated by 7 ° in order to limit the risk of fuel overflowing. It is also less sensitive to changes in altitude and variations in temperature..
Year after year, KTM engineers strive to make their motorcycles lighter. The result is clear: the 2018 KTM SX models are among the lightest and slimmest motocross bikes on the market.
Sophisticated ‘zero dirt’ footrests prevent gear selector clogging even when driving through deep ruts. The driving position is not high enough? Never mind! The footrest mounting system of the EXC models of the AM 2018 has been raised by 6mm compared to that of the SX versions.
AIR FILTER BOX
The air filter housing has been designed to better protect the air filter against clogging and to ensure optimum air flow. The cage in which the extra-large Twin Air air filter is housed is completely rigid, which helps to better hold the system in place. The design is so simple that you could replace the filter even with your face covered in mud. And this without the help of any tool. And in a matter of seconds.
The high-tech chrome-molybdenum steel frame, a model of lightness, flexibility and maneuverability, offers excellent stability and proves devilishly precise in turns. Thanks to its high torsional rigidity and low longitudinal rigidity, this frame allows better absorption of the energy generated by the front and rear suspensions when jumping or crossing a bump. Driving is more comfortable and less taxing. The mounting brackets that ensure the connection between the cylinder head and the frame are still just as light. Mounted laterally, they also help to limit the level of vibration and to refine the trajectory of the motorcycle in the bends. Engineers can be proud of their work because the frame is now a kilo lighter than the lightest competitive frame available on the market today. Everything has also been done to facilitate maintenance and free up space for the tank and other components. The ultra-light rear part of the frame, made of stable aluminum profiles, weighs less than 900grams on the scale.
In addition to a significant saving in weight, cast aluminum has an ideal bending behavior. The one-piece molding process eliminates the imperfections inherent in welding and guarantees a more consistent build quality, but also more careful.
When it comes to handlebars, KTM engineers have always known which direction to go. Contoured and made of high-strength aluminum, this handlebar is no exception to the rule. It is fitted with rubber shock absorbers and can be adjusted to two positions. The ODI handle is very practical to change if necessary, thanks to its mounting system without glue or wire.
The ultra-light polyethylene tank has a capacity of 7.0 liters. Tank cap with internal thread ensures easy and reliable closing.
Featuring ultralight CNC machined hubs and premium Excel rims, the wheels guarantee maximum stability despite limited unsprung weight. They are fitted with the latest generation Dunlop Geomax MX 3S tires.
KTM’s proven integrated cooling system circulates the coolant from the cylinder head through the frame wishbone to the aluminum radiators supplied by WP. Its incredible efficiency is due to the better management of the internal air flow and the progress made in ventilation thanks to CFD calculations (numerical simulation in fluid mechanics). The new radiator guards offer the advantage of better heat dissipation. This is all the more true in the presence of mud. Integrated into the front part of the spoilers, these radiator guards are particularly useful in the event of an impact.
All KTM factory riders have collaborated on the design of the bike with KTM R&D specialists and the Kiska design agency, with a single watchword: to create a perfect harmony between the rider and the machine. Particular attention has been paid to ergonomics and contact points to enhance freedom of movement on the SX. The particular shape of the front and rear mudguards guarantees maximum stability and minimum weight, thanks to a well-thought-out structure and assembly. Better yet: they stay clean longer.
Custom graphics kit, Factory orange frame: every detail counts, because in this discipline, there is nothing more beautiful than a racing car that stands out from the rest.
The WP shock absorber has been developed taking into account the architecture of the frame and the swingarm, just like the linkage system and the WP AER 48 fork. With its various machined and black anodized components, this ultra-sophisticated shock absorber is strong. impression compared to competing products less well finished. It benefits from a new setting that inspires confidence and optimized damping characteristics that go hand in hand with the setting of the front axle. The shock features shiny colors, hallmarks of the WP brand.
Another interesting novelty on this bike is the WP AER 48 inverted fork with air spring and separate damping circuits, developed by WP in close collaboration with KTM. Damping functions are 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 hold the motorcycle in position. The air spring is easily adjusted according to the weight of the pilot using a single valve. No special tools are required – the standard air fork pump will do. The right fork leg incorporates a cartridge specially designed to adapt to the type of damping sought. Simply turn the 30-screen dial to the desired position (compression up and rebound down) to choose the appropriate setting based on track conditions and rider preferences. More comfortable and more sensitive than ever, this fork (with revised damping characteristics) begs to be put to the test.
High-quality CNC-machined triple trees, which ensure ultra-precise front end handling, have been a KTM hallmark for years. Two positions are possible for the handlebar trigger guard with shock absorber pads. The hour meter tells you when it’s time for a service.
These small technological gems are associated with Wave discs renowned for their lightness. More responsive, more efficient and more powerful than ever, Brembo brakes will tackle any situation.
What you must remember
your2018 KTM 250 SX
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The technical aspect
2018 KTM 250 SX
- Frame: Central tubular steel frame
- Tank: 7 liters
- Seat height: 960 mm
- Wheelbase: 1,485 mm
- Dry weight: 95 kg
- Train before
- WP inverted telehydraulic fork Ø 48 mm, deb: 310 mm
- 1 disc Ø 260 mm, 2 piston caliper
- 5-speed gearbox
- secondary by chain
- Rear axle
- WP mono-shock, deb: 300 mm
- 1 disc Ø 220 mm, 1 piston caliper
- Single cylinder
, 2 stroke
- Cooling: by water
- Carburetor Ø 38 mm
(66.4 x 72 mm)
- Weight ratio /
kg / hp
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