Motorcycle specifications KTM125 SX 2017 Tone and lightness

The 125 SX has been going strong on the market for many years. And according to KTM, it still has many good years ahead of it. It’s worth noting that it’s been meticulously refined: they’ve kept a close eye on its design and eliminated every single unnecessary gram. The 2-stroke engine and chassis have also received a great deal of attention. Its power is going to be a force to be reckoned with.

ENGINE

The latest 125 SX engine stands out as the most powerful and competitive in its class, proving that 2-stroke technology has a bright future ahead, thanks to its excellent power-to-weight ratio, low cost, and simplicity. This 125cc engine, the result of KTM’s technical expertise, incorporates the latest technological innovations on the market. Despite its compact design and a weight of just 17.2 kg, it delivers impressive power across the entire rev range. The rider has everything needed to set the fastest lap times.

CYLINDER

This ultra-compact cylinder, with a 54 mm bore, features state-of-the-art exhaust control and a sophisticated mechanism for the side-mounted exhaust ports. Combined with the two-piece cylinder head, this design results in a significant increase in power across the entire range. The arrangement of the water jackets inside the cylinder and cylinder head allows for efficient heat dissipation during high engine loads.

ENGINE CASING

For the latest generation of engines, KTM engineers have designed ultra-lightweight cast engine cases. They have also raised the position of the crankshaft to bring it closer to the center of gravity, thereby better centralizing the masses and enhancing riding comfort. Despite its extremely compact design, the engine can accommodate an optional electric starter.

CARBURETOR

Starting with the 2017 model year, all KTM 2-stroke models will be equipped with the new MIKUNI TMX carburetor instead of the usual Keihin carburetor. This 38 mm flat-slot carburetor delivers a significant improvement and better power delivery across the entire operating range. It is also less sensitive to changes in altitude and temperature fluctuations.

GEARBOX

Another interesting innovation designed specifically for the 2-stroke engine: a robust 6-speed gearbox perfectly suited to the 125’s operating range. The engine’s reduced weight and compact size were made possible through the use of state-of-the-art production technologies. Since safety is also a key consideration, the gear selector features a new “zero-dirt” design that prevents the lever joint from seizing up due to dirt buildup. Because even off-road enthusiasts don’t like mud when it gets in the wrong places.

EXHAUST

The combustion chamber has been meticulously engineered to deliver even more power and torque. This engine is a marvel of explosive power and durability.

87.2 kg

The primary goal of KTM engineers during the development of the new generation of SX models was to achieve significant weight reduction and improved handling. The result speaks for itself: the current SX models are among the lightest and most agile bikes in competition.

FRAME

The high-tech chrome-molybdenum steel frame, a model of lightness, flexibility, and maneuverability, offers excellent stability and proves to be devilishly precise in corners. Thanks to its high torsional stiffness and low longitudinal stiffness, this frame allows for better absorption of the energy generated by the front and rear suspension during a jump or when crossing a bump. Riding is more comfortable and less taxing. The mounting brackets connecting the swingarm to the frame are as lightweight as ever. Mounted laterally, they also help reduce vibration and refine the bike’s trajectory in corners. The engineers can be proud of their work, as the frame now weighs one kilogram less than the lightest competing frames available on the market today. Every effort has also been made to simplify maintenance and free up space for the fuel tank and other components. The ultra-light rear section of the frame, composed of rigid aluminum profiles, weighs less than 900 grams.

FOOTREST

The sophisticated “zero-dirt” footrests prevent the gear selector from getting dirty, even when riding through deep ruts.

AIR FILTER HOUSING

The air filter housing enhances protection of the air filter against clogging and ensures optimal airflow. The housing that holds the extra-large Twin Air air filter is completely rigid, which helps keep the system securely in place. The design is so simple that you could replace the filter even with your face covered in mud. And you can do it without any tools. All in just a few seconds.

SWING ARM

In addition to significant weight savings, cast aluminum offers ideal flex characteristics. The monobloc casting process eliminates imperfections inherent in welding and ensures a more consistent and refined build quality.

FUEL TANK

The ultra-lightweight polyethylene fuel tank has a capacity of 7 liters. The fuel cap with an internal thread ensures easy and reliable closure.

HANDLEBAR

When it comes to handlebars, KTM engineers have always known which direction to go. Profiled and made of high-strength aluminum, this NEKEN handlebar is no exception. It is equipped with rubber silent blocks and can be adjusted to two positions. Starting with the 2017 model year, the handlebar is secured using two clamps (lower section) and a new bridge (upper section) that improves torsional rigidity. Replacing the handlebar is also easier should it ever bend following a nasty crash. Right: an ODI vulcanized grip; left: the ODI lock-on grip, which is as comfortable as it is practical, thanks to its mounting system that requires no glue or wire.

SADDLE

Custom-shaped to provide a comfortable seating surface, this saddle is as durable as it is comfortable. Riders are in for a treat with a new saddle cover on the 2017 AM designed to enhance grip and feel.

COOLING SYSTEM

KTM’s proven integrated cooling system circulates coolant from the cylinder head through the frame triangle to the aluminum radiators supplied by WP. Its incredible efficiency stems from improved internal airflow management and advancements in ventilation achieved through CFD (computational fluid dynamics) calculations. The well-designed radiator guards integrated into the front of the spoilers are particularly useful in the event of an impact. Every detail counts for KTM.

WHEELS

Featuring ultra-lightweight CNC-machined hubs and high-end Excel rims, the wheels ensure maximum stability despite limited unsprung weight. They are equipped with the latest-generation Dunlop Geomax MX 3S tires.

FORK

Another interesting new feature on this bike: the WP AER 48 inverted fork with air spring and separate damping circuits, developed by WP in close collaboration with KTM. The damping functions are on the right, the air spring is on the left. The left fork leg features a dual-chamber system and air cartridge designed to prevent any loss of pressure. If the outer seal were to leak, the pressure inside the inner cartridge would keep the bike upright. The air spring is easily adjusted to the rider’s weight using a single valve. No special tools are required: the standard-issue pump will do the job. The right fork leg incorporates a cartridge specifically designed to adapt to the desired type of damping. Simply turn the 30-click dial to the desired position (compression at the top and rebound at the bottom) to select the appropriate setting based on track conditions and rider preferences. For the 2017 model year, it’s also important to note that the outer tubes of the AER 48 fork have been redesigned to optimize flex characteristics, provide greater suppleness, and reduce friction. They’ve also shed 265 g, which is far from insignificant. More comfortable and responsive than ever, these forks are just waiting to be put to the test.

FORK CROWN

High-quality CNC-machined fork crowns have been a KTM trademark for years. Enabling precise handling, they significantly enhance flex characteristics and, consequently, fork performance. For the 2017 model year, the upper fork crown design has been revised to accommodate the new stanchions. The handlebar, equipped with rubber silent blocks, is secured using two clamping brackets (lower section) and a new bridge (upper section) that improves torsional rigidity. Replacing the handlebar is also easier, for example in the event of a crash. An odometer, mounted on the upper triple clamp, indicates when it is time for maintenance or refueling.

SHOCK ABSORBER

The WP shock absorber was developed with the new frame and swingarm architecture in mind, as were the linkage system and the WP AER 48 front fork. With its various machined and black-anodized components, this ultra-sophisticated shock absorber makes a strong impression compared to less well-finished competing products. It features new tuning and a softer spring that complement the new front-end setup.

BRAKES

More responsive, more effective, and more powerful than ever, the Brembo brakes are up to any challenge. These technological gems are paired with Galfer Wave discs, renowned for their lightness. For the 2017 model year, the rear brake pedal has been extended by 10 mm, and the new brake pads are now less aggressive.

FAIRING

KTM factory riders collaborated on the bike’s design with KTM R&D specialists and the Kiska design agency, with a single goal in mind: to create perfect harmony between rider and machine. Ergonomics and rider contact points have been carefully refined for maximum freedom of movement. The lowered seat offers superior comfort, particularly in the rear section. The unique shape of the front and rear fenders is a perfect example of intelligent design: thanks to a well-thought-out structure and mounting, these fenders ensure maximum stability while being lighter. Better yet: they stay clean longer.

Credit for information and images: KTM