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In the world of motocross, the new 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 needed to excel on any type of circuit and terrain and an unusual sense of placement thanks to its ultra-light chassis, the darling of KTM’s R&D teams and motorsport specialists is destined to become the future king of the discipline.
MOTOR
The 250 SX’s 2-stroke engine has long had a reputation as the most powerful engine in its class. All the hopes placed in this segment have borne fruit 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. To put its convictions into practice, KTM completely overhauled the engine structure of the 250 SX and made numerous improvements: new shaft assembly guaranteeing better mass centralization, new exhaust-controlled cylinder with double exhaust valve TVC, new 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..
CYLINDER
The cylinder of the 250 SX, with a bore of 66.4 mm, benefits from all new ports and a completely redesigned exhaust control. Thanks to a sophisticated mechanism for the exhaust channels of the side carrier, the power output is smooth. It is also possible to change the character of the engine in the space of a few seconds by adjusting the two exhaust control springs provided for this purpose. Whatever the condition of the track, we are sure to find the most suitable settings. Nothing has been left to chance: the new water jackets inside the cylinder and the cylinder head have the effect of better dissipating the heat. Ultra-light, the side mounting brackets of the cylinder head have been reworked to give more rigidity to the engine-frame assembly.
CRANKCASE
To improve mass centralization, engineers have chosen to raise the clutch shaft and crankshaft by 8 and 27 mm respectively inside the all-new molded crankcases, which translates into exceptional road holding. This trick also made it possible to free up space to install a balance shaft, to swallow the kilometers at full speed and in a relaxed manner. Another interesting innovation to keep the engine as radiant as in the early days: new engine covers with an elaborate surface structure, intended to reduce the wear caused by the rider’s boots.
BALANCING SHAFT
Numb hands or feet are not inevitable. The new engine design has made it possible to use a lateral balance shaft which helps to significantly reduce the level of vibration (50% less at the handlebars and footrests). This obviously has a beneficial effect on driving pleasure..
CARBURETOR
From MY 2017, all KTM 2-stroke models will be fitted with the new MIKUNI TMX carburetor instead of the usual Keihin carburetor. This 38 mm flat-valve carburetor allows a clear improvement and a better dosage of power over the entire range of use. It is also less sensitive to changes in altitude and variations in temperature..
CRANKSHAFT
A model of reliability, the engine has been expertly balanced to minimize vibrations. Thanks to the replacement of the cylinder, piston and cylinder head, the displacement now reaches 144 cm3. Since the crankshaft remained the same, the engineers killed two birds with one stone.
CLUTCH
The 250 SX uses a DDS (Damped Diaphragm Steel) clutch developed by KTM; it has a wear-free steel clutch housing and clutch discs offering very high heat resistance. This design is distinguished by the use of a diaphragm spring instead 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 housing has become lighter, the clutch hub has been reworked and the pressure plate helps optimize oil supply and cooling. The Brembo hydraulic clutch mechanism plays an essential role in the progressiveness and operation of the clutch..
GEARBOX
Even though this new 5-speed gearbox provides the same gear ratios as its predecessor, engineers have been keen to make shifting even smoother and more precise. As safety is also an essential parameter, the selector adopts a new “zero dirt” design which prevents blocking of the lever joint by soiling. Because even lovers of soft ground take a dim view of mud when it gets lodged in the wrong places..
EXHAUST
Attention has been paid to the combustion chamber to deliver even more power and torque. This engine is a marvel of explosiveness and solidity.
FRAMEWORK
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 900 grams on the scale.
FOOTREST
Sophisticated “zero dirt” footrests prevent gear selector clogging even when driving through deep ruts.
AIR FILTER BOX
The air filter housing reinforces the protection of the air filter against contamination and guarantees 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 one could replace the filter even with the face covered in mud. And this without the help of any tool. And in a matter of seconds.
SWINGING ARM
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.
PETROL TANK
The ultra-light polyethylene tank has a capacity of 7 liters. Tank cap with internal thread ensures easy and reliable closing.
HANDLEBAR
When it comes to the handlebars, KTM engineers have always known which direction to go. Profiled and made of high resistance aluminum, this NEKEN handlebar is no exception to the rule. It is equipped with rubber silent-blocks and can be adjusted to two positions. From MY 2017, the handlebars are fixed by means of two clamps (lower part) and a new trigger guard (upper part) which improves torsional rigidity. Replacing the handlebars is also easier if it should bend from a bad fall. Right: an ODI vulcanized grip; on the left: the ODI lock-on handle as comfortable as it is practical, thanks to its mounting system without glue or wire.
SADDLE
Tailor-made to provide a comfortable support surface, this saddle is as resistant as it is comfortable. Pampered, the riders will benefit from a new saddle cover on the AM 2017 intended to reinforce the grip and the feeling..
SYSTÈCOOLING ME
KTM’s proven integrated cooling system circulates the coolant from the cylinder head through the frame triangle to the aluminum radiators supplied by WP. Its incredible efficiency is due to the better management of the internal air flow and to the progress made in ventilation thanks to CFD calculations (numerical simulation of fluid mechanics). Well thought out, the radiator guards integrated into the front part of the spoilers are particularly useful in the event of an impact. Every detail counts for KTM.
WHEELS
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.
FORK
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 pump will do. The right fork leg incorporates a cartridge specially designed to adapt to the type of damping sought. Just turn the dial 30 stops to the desired position (compression up and rebound down) to choose the appropriate setting based on track conditions and rider preferences. For the AM 2017, it is also important to point out that the outer tubes of the AER 48 fork have been redesigned to optimize the bending characteristics, provide more flexibility and limit the frictional forces. They also lost 265g, which is far from insignificant. More comfortable and more sensitive than ever, these forks beg to be put to the test.
FORK TEE
High quality CNC machined triple trees have been a hallmark of KTM for years. Allowing precise steering, they significantly enhance the flexibility characteristics and, thus, the action of the fork. For the AM 2017, the design of the upper triple clamp has been revised and corrected according to the new divers. The handlebars are fitted with rubber silent-blocks by means of two clamps (lower part) and a new trigger guard (upper part) which improves torsional rigidity. Replacing the handlebars is also easier, for example in the event of a fall. An hour meter, installed on the upper triple clamp, indicates when it’s time to perform maintenance or refuel.
SHOCK ABSORBER
The WP shock absorber has been developed taking into account the new architecture of the frame and the swingarm, just like the link system and the WP AER 48 front fork. With its various machined and black anodized components, this ultra-sophisticated shock absorber makes strong impression compared to competing products less well finished. It benefits from a new adjustment and a more flexible spring which go hand in hand with the new setting of the front axle..
BRAKES
More responsive, more efficient and more powerful than ever, Brembo brakes will tackle any situation. These small technological gems are associated with Wave discs from Galfer, renowned for their lightness. For AM 2017 the rear brake pedal has been lengthened by 10mm and the new brake pads are now less aggressive.
FAIRING
The KTM factory riders collaborated on the design of the bike with the KTM R&D specialists and the Kiska design agency, with a single watchword: to create a perfect harmony between the rider and the machine. The ergonomics and the contact points for the pilot have been particularly taken care of for maximum freedom of movement. The lowered saddle offers superior comfort, especially in the rear shell. The special shape of the front and rear mudguards is a perfect example of intelligent design: thanks to a well-thought-out structure and assembly, these mudguards guarantee maximum stability, while being lighter. Better yet: they stay clean longer.
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8,255 €
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Replaces
250 SX 2016
Model marketed in
2012
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2014
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2017
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2020
The technical aspect
2017 KTM 250 SX
- Frame
- 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
- Front wheel:
80/100
– 21
- Transmission
- 5-speed gearbox
- secondary by chain
- Rear axle
- WP mono-shock, deb: 300 mm
- 1 disc Ø 220 mm, 1 piston caliper
- Rear wheel:
110/90
– 19
- Motor
- Single cylinder
in line
, 2 stroke - Cooling: by water
- Carburetor Ø 38 mm
-
249 cc
(66.4 x 72 mm) -
≈ 55
ch - Weight ratio /
power
: 1.73
kg / hp - Crit’air:
Detached pieces
exhaust
motor
fluid
electricity
filtration
braking
chain kit
Competitors
Yamaha YZ 250 2017
Gallery
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