The 2021 KTM 450 SX-F is the championship-winning bike from the Austrian company that has won year after year of 450cc class four-stroke motocross and supercross. It has a lightweight alloy frame cradling 450cc’s of raw four-stroke power, which equates to just over 63 HP.
KTM seems to have the formula to success, as the 450 SX-F only weighs 2.5 pounds more than the 350 SX-F, which in and of itself was a super light bike. Electronic fuel injection, a single overhead camshaft, and some very tricky valve management allow the engine to be the lightest in its class, while also being one of the most powerful in the 2021 lineup.
WP suspension is standard, of course. Brembo brakes and hydraulics are also par for the course. The biggest change the 450 SX-F sees is that its front brake is a whopping 260mm disc, compared to the 220 to 230 mm discs on lower spec models.
There is also a 450 SX-F Factory Edition, which adds an Akrapovič titanium exhaust, a racing connectivity unit to review laps, KTM factory competition wheels, a carbon-composite skid plate, a semi-floating front brake disc, and a full Red Bull Racing graphics kit. It also features the same Hinson clutch that the KTM Dakar Racing Team use on their 450 Enduro bikes, meaning endurance and race proven clutch feel.
The 2021 KTM 450 SX-F starts at $10,199 USD / $11,699 CAD, while the 450 SX-F Factory Edition starts at $11,299 USD / $13,099 CAD.
On this page:we’ve curated specs, features, news, photos/videos, etc. so you can read up on the new 2021 KTM 450 SX-F in one place.
The 450 cc engine is the ultimate powerhouse when it comes to KTM’s competitive motocross range. Its compact, lightweight design features a single overhead camshaft cylinder head, fueled by the latest electronic injection system. This enables the impressive power to be distributed extremely efficiently throughout the rev range. Even with its super-beneficial electric starter, this model is still the lightest 450 cc engine on the MX market.
Cylinder head
The KTM 450 SX-F is fitted with a lightweight, compact SOHC (single overhead camshaft) cylinder head. The design focusses on mass centralization, contributing to overall handling excellence. The overhead camshaft has a friction-optimized surface and valve timing that delivers impressive responsiveness. The four ultra-lightweight titanium valves (intake 40 mm, exhaust 33 mm) are activated via extremely rigid rocker arms. The rockers on the intake side are DLC coated, allowing for impressive engine speeds to 11,500 rpm. Low-friction chain guides further support the high RPM levels. The innovative head configuration guarantees the most efficient delivery of the unrivalled power, maintaining a strong edge over the competition.
Crankshaft
The crankshaft on the KTM 450 SX-F is located in an ideal position close to the center of gravity, contributing to better mass centralization. It utilizes a short connecting rod, which allows for a compact motor design and a snappier power delivery. The whole unit is extremely well-balanced, with the perfect amount of inertia for optimal traction and rideability. A plain big end bearing with two force-fitted bearing shells runs directly on the crank pin, with the necessary oil feed for this bearing supplied by the engine’s pressure lubrication. This design also enhances durability, allowing for long crankshaft service intervals – resulting in less effort and cost and more time spent on two wheels.
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 better 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 transmission on the KTM 450 SX-F is focused on lightweight performance without compromise to durability. There was no need to change the gear ratios as they have been perfectly matched to the power delivery of the large displacement engine, but the secondary drive (sprockets) ratio has been made shorter (13/49) for improved response. All four-stroke engines are fitted with a gear sensor, which provides the option of different engine characteristics for each gear, depending on engine load. An advanced “no-dirt” gear lever design prevents dirt from building up and together with the reliable gearbox, guarantees that the next gear is always an easy click away.
Frame
As with the entire KTM SX range, the frame on the KTM 450 SX-F is professionally crafted from hydroformed chromium molybdenum steel tubes that are robot welded to ensure the highest levels of consistent quality. The precisely 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.
Swingarm
The KTM 450 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.
Seat
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.
Battery
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.
