- What you must remember
- Make your2019 KTM 250 SX
- The technical aspect
- Related articles
The KTM 250 SX is an excellent combination of weight and power or between performance and control. With its high-performance 2-stroke engine and state-of-the-art chassis, it is undoubtedly one of the fastest 250cc 2-stroke on the circuit.. This racing beast is the ideal choice for speed enthusiasts who particularly like the characteristic 2-stroke sound..
The KTM 250 SX’s engine is the ultimate in 2-stroke technology, featuring a vibration-damping balance shaft and ultra-reliable hydraulic DDS clutch. The TVC double-valve control shaft is a major asset of the KTM 250 SX engine, rightly considered to be the most competitive 2-stroke in its class. Improvements to the cylinder and exhaust enhance the convenience of the 5-speed gearbox.
The cylinder of the KTM 250 SX, with a bore of 66.4 mm, has a control shaft managed by a TVC valve. The exhaust channel of the 2019 models has been machined to ensure more precise operation of the control shaft and to increase the overall level of performance. It is also possible to easily and quickly change the character of the engine thanks to the two springs provided for this purpose, so as to find the ideal settings (depending on the track or the preferences of the pilot). The cylinder head side mounting brackets are now made from aluminum instead of steel to almost completely dampen vibrations.
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 crankcase design enabled KTM engineers to bring the shaft assemblies closer to the center of gravity, so as 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 very strong 5-speed gearbox lends itself to all motocross tracks. The gears are perfectly adapted to the power delivered by the 250 cm engine³. Another strong point of this 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.
No more numb hands or feet. The engine design allowed for the addition of a lateral balance shaft which helps to minimize vibration. Driving at a sustained pace for long hours is therefore all the less taxing.
The KTM 250 SX is fitted with a heavy-duty DDS (Damped Diaphragm Steel) clutch developed by KTM. This features a wear-free steel clutch housing and heat-resistant clutch discs. The use of a diaphragm spring instead of the usual coil springs also gives it greater flexibility. The diaphragm spring also has the advantage of being compact, which makes it possible to integrate a damping system in the clutch hub, to gain traction and durability. The Brembo hydraulic clutch system is also distinguished by its precision and progressiveness..
The KTM 250 SX is fitted with a MIKUNI TMX carburetor. The settings of this 38mm flat-valve carburetor have been matched to the new air filter housing and exhaust structure to ensure a more linear and better balanced power delivery across the entire rev range..
All 2-stroke 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 crankshaft, with a stroke of 72 mm, guarantees superior maximum torque and power. Perfectly balanced, it is associated with a balance shaft to minimize vibrations. Ideally placed for optimal mass centralization, it helps strengthen the agility and handling of the bike..
Maintaining optimum engine temperature is essential to ensure consistent power delivery. The KTM 250 SX can count, for this purpose, on new radiators lowered by 12 mm compared to its predecessor. This position, perfectly suited to the design of the new spoilers, lowers the center of gravity and improves ergonomics. Thanks to computational fluid mechanics (CFD) computational simulation calculations and the clever 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 are the conditions. The special protections fitted to the radiators 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 new exhaust system gives the engine a smoothness and liveliness that are difficult to match. Its shape also brings a real plus in terms of ergonomics, while respecting the noise emission levels recommended in competition..
The chassis contributes to the feeling of osmosis between the pilot and his machine. The new chassis of the KTM 250 SX has not only been designed to mitigate the effects of the many irregularities in motocross terrain, but also to provide excellent feedback to the rider. The high-tech chrome-molybdenum steel frame provides the flexibility to absorb bigger shocks and boost the bike’s agility and stability at high speeds. For the 2019 model year, the engine has been raised by 1 ° from the swingarm axis to improve handling and front wheel grip. Improvements to the new chassis enhance the exhilarating handling of the KTM 250 SX.
The chrome-molybdenum steel frame of the KTM 250 SX is completely new. It consists of hydroformed tubes assembled by automated welding, so as to guarantee the highest levels of quality and homogeneity. The flexibility of the frame has been specially calculated to offer the best possible compromise between agility and comfort. The excellent cohesion with the suspensions also guarantees excellent stability at high speed. With the self-cleaning “zero dirt” footrests that won’t jam when pulled back into position, you are in complete control, whatever the conditions. The engine of the KTM 250 SX has been raised by 1 ° from the axis of the swingarm, to improve handling and grip of the front wheel. New aluminum brackets have been provided to make the bike lighter. The frame of all 2019 SX models inherits the heavy-duty powder coating (used on KTM Factory machines) and standard frame guards. The rear buckle, made of lightweight aluminum, has been lengthened by 40mm to improve the stability of the rear shell.
The KTM 250 SX has an optimized one-piece swingarm providing 5mm of additional play in the axle housing. This allows the wheelbase to be adjusted to suit conditions to better negotiate pins on motocross tracks or to enhance straight-line stability when the pace picks up. Obtained by high pressure die casting, the one-piece swingarm offers maximum strength at minimum weight. The chain measurement marks shown on the swingarm are clearly 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 heads on the 2019 models have been revised to limit the frequency at which the spokes need to be retensioned. The wheels are fitted with the latest generation Dunlop Geomax MX 3S tires, to maximize power transfer to the ground and gain stability.
All full-size SX models feature the ultra-light WP AER 48 fork. The legs of this 48mm inverted air fork have different function, 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 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 includes a cartridge specifically designed to meet the demands of the single damping arm design and can be adjusted to suit track conditions or rider preferences. All you have to do is turn the dial 30 notches to the desired position (compression up and rebound down). New damping settings on 2019 models improved front axle control and feel.
The DDC shock absorber, present on all SX models, has been developed taking into account the new architecture of the frame and the swingarm, as well as the link system and the AER 48 front 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. The settings and the main piston inside the shock have been revised to improve damping characteristics along with the new nose gear setting. Fully configurable in high speed and low speed compression, it can be adapted specifically to track conditions or rider preferences.
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 SX range feature a new, ultra-light polyethylene fuel tank. The capacity on standard size SX models is still 7 liters, but the shape of the tank is more ergonomic. Fuel tank cap with internal thread ensures easy and reliable closing.
Air filter housing
The KTM 250 SX’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 clogging. 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.
The saddle of all SX models has been redesigned to confirm the improvements made in terms of ergonomics. The saddle cover now incorporates silicone bands designed to optimize grip and feel. A long screw inserted on the side helps to better fix the saddle to the motorcycle and makes handling easier and safer.
All full-size SX models feature the same super strong aluminum tapered handlebar, 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. The handlebar foam has also been revised as well as the hand guard which is now much easier to put on or take off. This handlebar offers the level of control needed to stay in control of the track and excellent grip to support the impressive 2-stroke power..
Software and electronics
The new KTM 250 SX features electronics that match its ambitions. The hour meter (available as standard) keeps track of the hours spent in the saddle while the tachometer (available as an option) allows you to find the ideal speed.
What you must remember
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The technical aspect
2019 KTM 250 SX
- Frame: Central tubular steel frame
- Tank: 7.5 liters
- Seat height: 950 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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