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The KTM 125 SX is a treat to drive. It is one of the most compact and lightest models of standard size motorcycles. The combination of a lighter chassis and one of the most powerful 125cc 2-stroke engines in its class opens up new horizons for the most impetuous of young pilots.. More lively than ever, this 2-stroke allows you to learn and fill your collection of trophies before entering the profession..
Motor
The engine of the 125 SX once again asserts itself as the most powerful and competitive block in its class. Its excellent power-to-weight ratio, low cost and simplicity prove that 2-stroke technology has a bright future at KTM. This compact and durable 17.2 kg engine, the result of KTM’s technical expertise, delivers great power across the entire rev range. Precise and powerful, this engine enables excellent lap times and better results to be obtained..
Cylinder
The cylinder, with a bore of 54 mm, has undergone several improvements within the 125cc engine. It features an optimized control axis and a sophisticated mechanism for the side support exhaust channels. The new configuration of the exhaust channels helps to increase the performance level of the engine. The upper contour of these components has even been machined to ensure ultra-precise timing. Combined with the two-piece cylinder head, this reworked cylinder results in a marked increase in power over the entire rev range of the 125 SX..
Engine housings and covers
The use of the high pressure die casting process results in thin walls while maintaining the strength and durability of the crankcase. The design of the crankcase allowed KTM engineers to raise the position of the crankshaft in order to bring it closer to the center of gravity, in order to better centralize the masses and to reinforce the driveability. The lightness of the engine block owes a lot to the extremely compact shape of the engine housing. The intermediate kicker gear on the 2020 models has been redesigned to improve reliability.
Gearbox
The 125 SX has a robust 6-speed transmission. The transmission ratios of the previous version have been renewed, but the gears have been improved and reinforced. For added safety, the gearbox has a new balance shaft that holds the front toothed wheel with a bolt and diaphragm spring instead of a circlip. Another strong point of the transmission on the 125 SX 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.
Carburetor
The 125 SX features a 38mm MIKUNI TMX flat-valve carburetor with settings to match the new air filter housing introduced in 2019. The 2020 model valve boxes have received several functional and technical improvements. (improved tightness and reliability) to ensure linear power delivery over the entire rev range.
Contact
All 2-stroke models have a CDI box and advanced components designed to improve engine behavior when starting. The ignition curves have not changed.
Cooling
Maintaining optimum engine temperature is essential to ensure consistent power delivery. The 125 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 digital fluid mechanics (CFD) and the clever cooling system implemented, this innovative system ensures that the engine components are kept at the ideal temperature to guarantee the highest level of performance, whatever 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..
Quiet
The exhaust system, developed especially for this motorcycle, gives the engine a smoothness and liveliness that are difficult to match. Its particular shape brings a real plus in terms of ergonomics, while respecting the noise emission levels recommended in competition.
Frame
So that you can fully enjoy the exhilarating driving experience of a 125cc 2-stroke, KTM has developed a chassis that meets your ambitions. The high-tech steel frame is able not only to react instantly to the rider’s demands, but also to provide excellent feedback. Its flexibility has been specially designed to absorb the biggest shocks and enhance the agility and stability of the bike at high speed. 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 and allow the rider to remain totally in control of his mount..
Framework
The 125 SX’s frame and rear buckle promote the aggressive riding styles that are a must in the 125cc class. The frame is made of hydroformed tubes in chromium-molybdenum steel, assembled by automated welding, in order to guarantee the highest levels of quality. The rigidity has been specially designed to guarantee unparalleled handling. The excellent cohesion with the suspensions also offers the perfect compromise between agility and 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 frame of all SX models inherits the very durable lacquer coating (used on KTM Factory machines) and standard frame protectors. The rear buckle, made of lightweight aluminum, reinforces the stability of the rear shell and provides excellent support for the rider, despite its low weight.
Swinging arm
The one-piece swingarm, obtained by high-pressure die-casting, has been designed to offer rock-solid 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 and 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.
Wheels
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 fitted with latest generation DUNLOP Geomax MX 3S tires, to maximize power transfer to the ground and gain stability.
Front suspension
All full-size KTM SX models feature the ultra-light WP XACT AER fork. 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 includes 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..
Rear suspension
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 link 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 rider preferences.
Triple trees
All KTM SX models use high quality CNC machined triple trees, a hallmark of KTM. To account for the flexibility of the frame and fork, engineers have firmed the upper triple clamp (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 damping rubber intended to attenuate vibrations. Hour meter, standard on the upper triple clamp of all SX models, tracks hours spent in the saddle and indicates when it’s time for service.
Brakes
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..
Fuel tank
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 125 SX’s air filter housing optimizes flow dynamics. Combined with the intake snorkels, it ensures maximum power deployment and excellent recoveries. In addition to the obvious performance gain, the 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.
Ergonomics and comfort
It is essential to maintain a good dynamic to take care of your lap times on a 125 cm3. To keep an excellent pace, it is therefore crucial to be able to move quickly and easily on your motorcycle and to become one with it. To offer flawless ergonomics and guarantee an optimal level of performance, KTM engineers have made sure that the rider can adjust the position of the handlebars (according to his preferences and conditions) and adopt an ideal posture on his motorcycle. The way the rider interacts with the fairing, saddle, footrests and handlebars has a direct bearing on finding the point of balance and controlling the bike. As these elements did not allow any compromise, KTM has made every effort to choose the best in this area, both in terms of product quality and design. The 2020 125 SX instinctively gives the rider the impression of being in complete control. This feeling is confirmed from the first turns of the wheel.
Saddle
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 helps to better fix the saddle to the motorcycle and makes handling easier and safer.
Handlebar
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. Handlebar features handlebar foam as well as hand guards that are easy to put on or take off.
Footrest
Sophisticated ‘zero dirt’ footrests prevent gear selector clogging even when driving through deep ruts.
Software and electronics
The 125 SX has electronics to match its ambitions. Simplicity of 2-stroke in its purest form, the hour meter (available as standard) records the hours spent in the saddle while the tachometer (available as an option) allows you to find the ideal speed.
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Replaces
125 SX 2019
Model marketed in
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2020
The technical aspect
2020 KTM 125 SX
- Frame
- Frame: 25CrMo4 steel central tube frame
- Tank: 7 liters
- Seat height: 950 mm
- Wheelbase: 1,485 mm
- Weight in running order: 87.5 kg
- Train before
- WP inverted telehydraulic fork Ø 48 mm, deb: 310 mm
- 1 disc Ø 260 mm, 2 piston caliper
- Transmission
- 6-speed gearbox
- secondary by chain
- Rear axle
- WP mono-shock, deb: 300 mm
- 1 disc Ø 220 mm, 1 piston caliper
- Motor
- Single cylinder
in line
, 2 stroke - Cooling: by water
- Carburetor Ø 38 mm
-
124.80 cc
(54 x 54.5 mm) -
≈ 40
ch - Crit’air:
Detached pieces
exhaust
motor
fluid
electricity
filtration
braking
chain kit
Competitors
Gallery
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