2018 KTM 250 SX-F
2018 KTM 250 SX-F
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.
The KTM 250 SX-F engine is known to be the strongest engine in the 250cc class. 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 47.6 pounds. That’s including the incredibly beneficial E-starter.
The centerpiece of the compact DOHC engine is the cutting-edge cylinder head. It features two overhead camshafts, which activate the titanium valves via super-light finger followers with a hard DLC coating. New lateral brackets (now made of aluminum instead of steel) allow an efficient fixation of the engine to the frame and shave off even more weight.
The 250 SX-F has an extremely rigid crankshaft, which features a connecting rod with a plain big end bearing with two force-fitted bearing shells running directly on the crank pin. This design is a major prerequisite for the extremely high engine speed levels and the unrivaled maximum power of the 250cc engine. Not only that, it enhances the engine’s durability, allowing long crankshaft service intervals, which is a huge customer benefit in relation to time, effort and cost.
The 250 SX-F is fitted with an electric starter as standard, which is a clear advantage when it comes to crunch time in the heat of battle. A strong starter motor made by Mitsuba and the proven starter drive will fire time and time again at the push of a button.
CRANKCASES AND ENGINE COVERS
The design of the die-cast engine cases 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.
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 snappy as it is strong.
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 gate drops and maximum grip thanks to different maps that sync with to the gear you’re in. It’s also possible to unleash an even more powerful mapping via the handlebar map switch.
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.
KTM’s proven cooling system routes the coolant from the cylinder head through the frame triangle, directly to aluminum radiators made by WP. A new filler cap system and are stiffer alloy construction increase the durability and reliability of the cooling system. Due to flow optimized internal circulation and CFD-calculated air ventilation, the system is superbly efficient. In addition, well thought-out radiator guards integrated in the front part of the shrouds provide protection in a crash.
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. For 2018, the transmission shaft gets a new C4 bearing that has a bigger overlap in the case. This means reliability even under extremely hard conditions.
The side-mounted counter balancer does double duty also driving the water pump. Thanks to its perfect balance and low oscillating masses, engine vibration is kept to a minimum.