
01. Engine & Exhaust


Engine
Renowned as the strongest engine in 250 competition, the 2020 version maintains its dominance. Its compact structure contributes to excellent mass centralization, which supports the easy rideability of the bike. The 2020 model features a new, stronger oil pump intermediate gear that, along with several other small, but important refinements, contributes to improved reliability. The low weight of only 57.1 lbs, in combination with the compact engine layout and unrivalled power, once again makes the KTM 250 SX-F a real force to be reckoned with, yet still easy to ride for both amateur and professional riders.



Cylinder head
An integral part of the class-leading power delivery is the cutting-edge DOHC (double overhead camshaft) cylinder head. It features two overhead camshafts which activate the titanium valves (intake 32.5 mm, exhaust 26.5 mm) via the super-light, DLC coated finger followers. The camshafts have a friction-optimized super-fine surface and a timing that delivers incredibly refined power.



Crankshaft
The KTM 250 SX-F has a rigid crankshaft and a connecting rod that features a plain big end bearing with two force-fitted bearing shells running directly on the crank pin. This design was essential for the extremely high engine speeds and unrivalled maximum power of the 250 cc 4-stroke engine. The design also enhances the engine's durability, allowing long crankshaft service intervals, which is a huge benefit in terms of time, effort and cost.



Crankcases and engine covers
The compact engine cases are manufactured using a high pressure die-cast production process that helps with weight reduction, while retaining strength and durability. The design allows for optimal shaft arrangements close to the center of gravity, resulting in ideal mass centralization and easier rideability. The engine covers feature a smart surface structure that reduces wear caused by the rider's boots, keeping them looking as fresh as the day you bought it.



Transmission
The KTM 250 SX-F is fitted with a robust 5-speed transmission. The gear ratios were carried over from its predecessor and are perfectly suited for the MX track. Another highlight of the 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 management system
The state-of-the-art KEIHIN Engine Management System, with electronic fuel injection, features a 44 mm throttle body. The injector position guarantees optimal atomization of the fuel and air on the way to the combustion chamber, resulting in instant response and maximum performance when opening the throttle. There are also separate systems for cold starting and idle adjustment. The ECU features maps which have been developed to precisely match the exhaust and cylinder head, with options for regulating traction and launch control. It also provides different maps for each gear, according to the information received from the gear sensor, ensuring maximum power as you shift through the gears.



Cylinder and piston
The 78 mm bore cylinder houses a lightweight, forged, bridged, box-type piston, made to the highest standards by CP. It has an extremely rigid structure and features a unique crown shape to suit the high-compression combustion chamber. The compression ratio is at 14:4:1 and thanks to the combination of low oscillating masses, the engine displays extremely lively characteristics.



Balancer shaft
In order to balance the mass forces the KTM 250 SX-F produces, the engine is fitted with a multifunctional counterbalance shaft. It effectively reduces vibration, while driving the water pump and timing chain.



Clutch
The DS (diaphragm steel) clutch literally puts the control back in the hands of the rider. It features a durable, one-piece clutch basket and primary gear, made of high-strength billet steel, guaranteeing unbeatable reliability. It is fitted with extremely heat-resistant steel carrier friction discs, which are pre-tensioned by means of a diaphragm spring, ensuring the most effective disengagement of the clutch. This design substantially reduces the operating force required to pull the clutch and is made even easier with the BREMBO hydraulic system.



E-Starter
Time is crucial in the heat of the race and an electric starter gets you fired up and back in the battle as soon as possible. The electric starter is standard on the KTM 250 SX-F and features a strong starter motor made by MITSUBA. The proven starter drive guarantees efficient and reliable starting when you need it most.



Handlebar map select switch
Within easy reach of the left grip on all four-stroke models, is a multifunctional handlebar map switch, which features the innovative control functions; traction control; launch control and alternative power curves (standard - advanced). The TRACTION CONTROL is a unique feature that guarantees more efficient traction and better control when accelerating the bike, especially in challenging track conditions. It can be activated on the handlebar map switch while riding. With a simple push of the two buttons at idle speed, the rider can also activate LAUNCH CONTROL, ensuring the most effective launch out of the gate. The map switch also gives the rider the chance to select an alternative power map besides the standard configuration, providing him with options during the race.



Cooling
Maintaining the optimal engine temperature is crucial to ensuring consistent horsepower throughout the ride. The KTM 250 SX-F features radiators which are positioned for a lower center of gravity. Their design matches the shrouds perfectly and offers a great slim feel to the 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.



Exhaust
When it comes to power delivery and performance, the exhaust on all 4-stroke models plays a key role and packs a punch that is hard to beat. It features a model specific header pipe with an advanced resonator called FDH (Flow Design Header), which is a small chamber around the pipe. The design allows the exhaust to be disassembled without removing the shock absorber and also provides better access to the shock. The aluminum sleeve, end cap and internal design of the silencer allow for slimmer ergonomics, making the bike feel narrower, without compromise to regulatory noise limits.
