The 2021 KTM 250 SX-F is a true competitor, from the rawness of its power to the lightness of its frame. It’s been so successful as a two-stroke, that the European manufacturer put in the time and engineering to make a four-stroke version of the engine and bike for the 2021 model year, known as the 250 SX-F. The 250cc engine, like its 250 SX counterpart, makes just around 50 HP.
KTM has definitely done their homework, however, in separating the bikes between classes. The 250 SX-F four-stroke is more for the longer courses of supercross, and is able to participate in endurance rallies without much trouble. It can also go faster overall than the SX version, although it won’t get to its top speed quite as fast. The last key difference is that the SX-F has an electric starter, while the SX is kickstart only.
KTM Motorcycles kept the same chassis but with a few tweaks so that the bike can compete in several different forms of bike sport with the word “cross” as part of its name, be it motocross, supercross, or cross country. As with almost all KTM motocross bikes, it comes with WP racing suspension, disc brakes, and a 5-speed manual transmission with hydraulics by Brembo.
The 2021 KTM 250 SX-F starts at $9,299 USD / $10,599 CAD.
On this page:we’ve curated specs, features, news, photos/videos, etc. so you can read up on the new 2021 KTM 250 SX in one place.
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.
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.
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.
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.
The frame on the KTM 250 SX-F has to cater for the dynamic riding styles typical of the class it fits into. As with the entire SX range, the frame is professionally crafted from hydroformed chromium molybdenum steel tubes that are robot welded to ensure the highest levels of consistent quality. The carefully calculated stiffness of the frame delivers responsive handling and works perfectly with the suspension to provide excellent agility and high-speed stability. All 2020 KTM SX frames feature a highly durable powder coating and come with standard frame protectors. The subframe is made from lightweight aluminum and provides great feeling for the rider, as well as easy movement across the seat.
The KTM 250 SX-F’s one-piece swingarm is manufactured using a gravity die-cast production process, for exceptional strength at the lowest possible weight. It offers a wide range of adjustment for the rear wheel, allowing for a shorter wheelbase on tighter, twisty tracks, or a longer wheelbase for greater stability on longer, more choppy tracks. The swingarm’s chain measurement markings are visible from above, making adjustment simpler and more accurate.
All KTM SX models feature a seat that perfectly matches the range’s dynamic performance-oriented ergonomics. The seat cover features silicone strips that provide better feel and grip for the rider. The seat is conveniently fixed to the bike using one long, lateral screw, making it secure and easy to handle.
All SX-F models feature a capable, super lightweight 2 Ah Lithium-Ion starter battery, ensuring quick and effective starting of the engine, especially in cold weather conditions. The voltage regulator and condenser, as well as all the electrical components are packaged in a common area below the seat, making the entire system compact and reliable.