The KTM 250 SX-F has been on top of the MX2 World Championship for many years now and just added another world title to its crowded trophy cabinet. But that’s no surprise. The combination of a powerful and torquey engine in a lightweight and agile chassis is bound to place the KTM 250 SX-F onto podium after podium.
Engine & Exhaust
The KTM 250 SX-F engine is known to be the strongest engine in the MX2 paddock. It screams at the top of its lungs at 14,000rpm, but is equally happy producing tons of torque and power across the rest of the rev range. Its compact architecture contributes to an excellent mass centralization, supporting the rideability of the bike. And it only weighs 26.1kg. That’s including the incredibly beneficial E-starter.
The engine of the KTM 350 SX-F features a compact and very light (27.2kg) construction. Its DOHC (double overheard camshaft) design with lightweight titanium valves and DLC coated cam followers allows for lively but strong engine characteristics. Fitted with the latest electronic fuel injection system and an E-starter, it has an extremely wide usable speed range, high performance and incredibly efficient rideability. The KTM 350 SX-F engine shares the same layout as the one in the KTM 250 SX-F, its playful handling similar to a 250 machine resulting mainly from reducing the moving masses to a minimum.
The centerpiece of the compact DOHC (double overhead camshaft) engine is the cutting-edge cylinder head. It features two overhead camshafts, which activate the titanium valves via super-light cam followers with a hard DLC coating.
The KTM 250 SX-F’s crankshaft utilizes a short connecting rod, which makes for an overall compact and lightweight engine with a snappy power delivery. A plain big (bottom) end bearing with two force-fitted bearing shells runs directly on the crank pin. The necessary oil feed for this bearing is ensured by the engine’s pressurized lubrication. This design is a decisive benefit in terms of the crankshaft service interval, which can be lengthened due to the plain bearing. So just pin it, all day long.
Crankcases and engine covers
The design of the die-cast crankcases allows for minimal weight and a very centralized shaft configuration. This makes the engine short and compact, while contributing to an efficient centralization of masses. The engine covers also feature a solid surface structure, which reduces the wear caused by the rider’s boots. This way, your SX-F will keep looking better longer.
The reliable 5-speed transmission features a special surface treatment on the 2nd, 3rd and 4th gears for solid reliability. The advanced ´No Dirt´ gear shift lever design prevents dirt from jamming the joint of the lever and guarantees precise shifting even in the muddiest conditions. All 4-stroke SX-F engines are fitted with a gear position sensor for tailored engine mapping for each gear. In MY18, the transmission shaft gets a new C4 bearing that has a bigger overlap in the case. This means reliability even under extremely hard conditions. Think GP-level riding. In knee-deep sand.
Engine management system
The state-of-the-art Keihin Engine Management System with electronic fuel injection features a 44mm throttle body. Thanks to its unique injector position, the engine’s response is instantaneous. And to make life even easier, separate systems for cold starts and idle adjustment await you. The lightweight ECU features a unique traction and launch control system for lightning-quick response when the bar drops and maximized grip thanks to different maps that sync with to the gear you’re in. As an ultimate bonus, the rider can unleash an even more powerful mapping via the handlebar map switch.
Cylinder and piston
Inside the short cylinder, with a bore of 78mm, thumps a box-type piston made by CP. Its crown geometry is adapted perfectly to the high-compression combustion chamber (14:1), where its rigid structure and low weight shine. Thanks to the low oscillating masses, the engine is as cheerful as it’s strong.
The side-mounted balancer shaft does double duty also driving the water pump. Thanks to its perfect balance and low oscillating masses, engine vibration is kept to a minimum.
The KTM 250 SX-F employs the KTM-developed CSS clutch (coil spring steel) with a robust steel basket and extremely heat resistant clutch plates and new, nitrated steel liners reducing the wear. Light operation and telepathic amounts of control are standard with this hydraulic Brembo actuated clutch.
Like all KTM 4-stroke motorcycles, the 250 SX-F is started at the push of a button - a priceless advantage when you’re on the clock.
Handlebar map select switch
All 4-stroke models are equipped with a multi-functional handlebar map select switch, which does three things: Activation of the traction control Activation of the launch control Selection of an alternative power curve (Standard or Advanced) The traction control is a unique feature that none of the competitors can offer. It guarantees more efficient traction when the track conditions are less than perfect. Push the tip switch and reign supreme. With this map select switch the rider can also activate the launch control, which provides more efficient starts out of the gate so you can go for the holeshot, time and time again. How? It simply reduces the maximum engine speed for the very first moment of the start, in order to give you better control. Push both tip switches when the engine idles and the EFI control lamp mounted on the upper triple clamp will let you know you are READY TO RACE. In addition, the map select switch gives the rider the chance to select an alternative, more powerful map beside the standard configuration. Welcome to the future.
KTM’s proven cooling system routes the coolant from the cylinder head through the frame triangle, directly to aluminum radiators made by WP. Thanks to flow optimized internal circulation and CFD-calculated ventilation, the system is superbly efficient. In addition, new radiator protections improve heat dissipation. Especially in the mud. They are also integrated into the front part of the shrouds to protect the radiators in a crash.
FIM noise limits are a real challenge for every manufacturer. Therefore, KTM has put a lot of effort into the development of their exhaust systems. All 4-strokes are fitted with headers that have a unique standard feature; an additional resonator system – a small chamber connected to the pipe. All 4-strokes are fitted with a short silencer, mounted as close to the engine as possible. You know what that means: extra mass centralization and better rideability. Its advanced internal design reduces the noise sufficiently in order to sit safely below the noise limit, while still raising the hairs on your neck.
The main target for the KTM engineers when developing the SX models was a massive weight reduction compared to the previous generation. The result: the current SX-F models are the slimmest, lightest bikes in the competition, even though the 4-strokes are equipped with an electric starter as a standard feature, while the competition still needs to be kick started. You can just focus on kicking ass.
The high-tech, lightweight chrome-moly steel frame has a knack for easy handling, outlandish rideability, precise cornering and excellent stability. You can also count on high torsional rigidity and low longitudinal stiffness. This results in better absorption of the energy created from the front and rear suspension, sucking up jumps and bumps. In short: more comfort and less rider fatigue. Laterally attached, lightweight aluminum engine head stays (the connection between cylinder head and frame) contribute to more precise cornering and a reduced vibration level. The engineers were able to pull off all that, while making their frame a big fat kilogram lighter than that of the lightest competitor on the market. In addition, it is easier to maintain, easier to work on and supplies more space for the tank and other components. The bike also features an extra-light subframe made of stable aluminum profiles, which tiptoes the scales at less than 900g.
The cast aluminum design offers low weight and a perfect flex behavior. The single-component casting process eliminates any inconsistencies and inherent weak points created by welding. It’s better looking too.
The KTM wheels feature lightweight, CNC machined hubs and high-end Excel rims guaranteeing maximum stability at minimum weight. The wheels are fitted with the latest Dunlop Geomax MX 3S tires.
The lightweight WP AER 48 front fork, a 48mm USD air-sprung fork developed by WP in close collaboration with KTM, is a split fork with separate functions for each leg. That means damping functions are on the right side, whereas the air spring is in the left. This left leg features a 2-chamber system with a capsuled air cartridge to prevent loss of air pressure. Should the outer seal start to leak, the internal cartridge pressure will keep the bike in position. The air spring is easy to adjust to any rider weight via a single air valve. No special tools are required; the air pump supplied with the bike will do just fine. The right fork leg integrates a damping cartridge that tailors to all your damping needs. It can be adjusted to the track conditions and the rider’s preferences with a twist of a dial (compression from the top, rebound from the bottom, 30 clicks each). Right off the dealer floor, this fork (with reworked damping characteristics) is more comfortable and more sensitive than ever. But you can still hammer the hell out of it.
The WP shock absorber has been developed with the entire frame and swingarm architecture in mind, including the linkage and the WP AER 48 front fork. It features machined and black anodized components and is a valuable, high-end product compared to roughcast reservoirs. A new, confidence inspiring setting with improved damping characteristics perfectly matches the front-end setup and its sparkling WP color scheme lets everyone know you have excellent taste in suspension.
Top quality, CNC machined triple clamps have been a KTM trademark for years to ensure precise handling. The rubber damped handlebar fixation allows for two positions and an hourmeter is fitted in order to let the rider know it’s time for a service.
These high-tech Brembo babies are combined with lightweight Wave brake discs. You couldn’t brake any harder, better, faster or stronger.
A lightweight polyethylene tank with a capacity of 7.0 liters of juice. The filler cap has an inside thread, which makes for easy and reliable closure.
The airbox design offers maximum protection of the air filter against soiling, while ensuring maximum airflow. The large twin-air filter is mounted in a stiff cage, which at the same time holds the system in place. This design is so simple, you could still pop a fresh one in with a face full of mud. Without tools. In seconds.
Ergonomics & Comfort
Tailored to meet the needs of the world’s fastest backsides, this durable seat offers great comfort, while being 10mm lower to help you master the most challenging terrain.
KTM engineers sure know how to handle handlebars. This tapered one, made of high-strength aluminum, is fixed in damped rubber mounts and has two different positions. ODI lock-on grips make grip changes easy and do not require any wire or glue to be secured.
Sophisticated ´No Dirt´ footpegs prevent clogging of the footpeg pivot, even when digging in deep ruts. Looking for a higher riding position? Then just mount the footpegs of the MY2018 EXC models, which are 6mm higher than the SX versions
Bodywork & Graphics
KTM R&D, KISKA Design and all our factory riders had their say in shaping the plastics with one goal: complete harmony between rider and bike. Perfect ergonomics and contact points provide maximum comfort in movement on the SX-F. The I-beam structures of the front and rear fenders guarantee maximum stability and a low weight thanks to well thought-out construction and mounting. They also stay cleaner for longer.
A new, tailor-made kit and a Factory orange frame. Because in this sport, champs deserve to look the part regardless of the dirt.