125 SX 2020

Overview Engine & Exhaust Chassis Ergonomics & Comfort Bodywork & Graphics Software & Electronics

Engine & Exhaust

KTM 2-strokes have been tearing up MX tracks for decades and are undoubtedly the fastest on the track today. Thanks to years of ongoing development, these engines are the benchmark in performance and technology, with the perfect combination of power, weight and control. For 2020, small, but important refinements have been made, resulting in improved power delivery and reliability and through its melodic high-RPM screams, KTM125 SX continues to deliver thrilling high-performance harmonics.

Engine

Power progression

…The KTM 125 SX engine is undoubtedly once again the most competitive and powerful engine in its class. With an outstanding power-to-weight ratio, low cost and overall simplicity, it is clear that 2-strokes will continue to have a successful future at KTM. The compact and durable 17.2 kg engine was developed using the latest KTM engineering know-how, resulting in broad power across the rev range. Its easy rideability and outstanding performance are benefits that equate to faster lap times and better results.

Cylinder

…At the heart of the 125cc engine is a cylinder with a 54 mm bore. It features an improved power valve unit with a sophisticated mechanism designed for the lateral support exhaust ports. The exhaust port layout increases engine performance, while the upper contour of the exhaust port has been machined to ensure more accurate port timing. The two component cylinder head works in complete harmony with the cylinder to deliver outstanding performance across the entire rev range.

Crankcases and engine covers

…The lightweight engine cases are manufactured using a high pressure die-cast production process, keeping wall thickness to a minimum while retaining strength and durability. The design allows for a high crankshaft position which is located near to the center of gravity, resulting in optimal mass centralization and easier rideability. The engine body is extremely compact, which contributes significantly to the low engine weight. Additionally for 2020, the kickstart intermediate gear has been reworked for improved reliability.

Transmission

…The KTM 125 SX is fitted with a robust 6-speed transmission. The gear ratios, which featured improvements and reinforcements, were carried over from the predecessor. The gearbox features a new drive shaft which uses a screw for pinion fixation and diaphragm spring instead of a circlip, ensuring safer pinion fixation. Another highlight of the 125 SX transmission is the no-dirt gear shifter. Similar to the footpeg design, it prevents the build-up of dirt and ensures the next gear is always available, no matter what the conditions.

Engine

Factory spark plug

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POWERPART

150 Factory kit

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POWERPART

Factory piston

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POWERPART

Cooling

Highly effective cooling

…Maintaining the optimal engine temperature is crucial to ensuring consistent horsepower throughout the ride. The KTM 125 SX features radiators which are mounted 12 mm lower than the predecessors. This lowers the center of gravity and matches the design of the new shrouds perfectly in order to achieve perfect ergonomics. By using CFD technology (computational fluid dynamics) together with a clever coolant circuit routing, the innovative system ensures the optimum engine temperature for the highest performance, no matter what the conditions. The radiators also feature special protectors that serve not only as protection from flying rocks and debris but also as a brace that disperses energy around the radiators in the event of an impact.

Cooling

Radiator fan

…Indispensable in extreme conditions, this fan ensures more air, better cooling and maximum performance. It's in your own hands: The digital control allows you to adjust the switch-on temperature to the present conditions and to read off the current temperature at any time. The switch-on temperature can be set anywhere between 65°C and 95°C. The switch-off temperature is set automatically, and is always 1°C below the switch-on temperature.For installation on all models, you will need the auxiliary wiring harness 77711979000; for additional switching, the Y-distributor 77711979044 can also be installed.

POWERPART

Radiator protection

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POWERPART

Exhaust

For sound of power

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Exhaust

FMF Powercore 2.1 silencer

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POWERPART

FMF Titan Powercore 2.1 silencer

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POWERPART

FMF Factory Fatty expansion chamber

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POWERPART

CNC-parts

Factory control cover

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POWERPART

Oil plug

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POWERPART

Water pump cover

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POWERPART

The illustrated vehicles may vary in selected details from the production models and some illustrations feature optional equipment available at additional cost. All information concerning the scope of supply, appearance, services, dimensions and weights is non-binding and specified with the proviso that mistakes, printing, setting and typing errors may occur; such information is subject to change without notice. No rights may be derived from incorrect statements.

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125 SX 2020

Engine & Exhaust

Engine

Power progression

Cylinder

Crankcases and engine covers

Transmission

Engine

Factory spark plug

150 Factory kit

Factory piston

Cooling

Highly effective cooling

Cooling

Radiator fan

Radiator protection

Exhaust

For sound of power

Exhaust

FMF Powercore 2.1 silencer

FMF Titan Powercore 2.1 silencer

FMF Factory Fatty expansion chamber

CNC-parts

Factory control cover

Oil plug

Water pump cover

The Company

Dealer & Service

News & Events

Legal

125 SX 2020

Engine & Exhaust

Engine

Power progression

Cylinder

Crankcases and engine covers

Transmission

Engine

Factory spark plug

150 Factory kit

Factory piston

Cooling

Highly effective cooling

Cooling

Radiator fan

Radiator protection

Exhaust

For sound of power

Exhaust

FMF Powercore 2.1 silencer

FMF Titan Powercore 2.1 silencer

FMF Factory Fatty expansion chamber

CNC-parts

Factory control cover

Oil plug

Water pump cover

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