The engine of the KTM 350 SX-F features a compact and very light (60lbs) 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 250 SX-F, resulting in its playful handling similar to a 250 machine by from reducing the moving masses to a minimum.
The cylinder head features two overhead camshafts with friction-optimized cam followers boasting a DLC coating and high-flow ports. Four lightweight titanium valves maximize the flow rate for an optimal power band and outstanding performance across the seemingly endless rev range of 13,400rpm. Lateral brackets made of aluminum allow an efficient fixation of the engine to the frame and contribute to the bike’s featherweight feel.
Cylinder and piston
Inside the short cylinder, with a bore of 88mm, 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 both snappy and strong.
The KTM 350 SX-F is fitted with a unique E-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 will fire time and time again at the push of a button. Even under extreme conditions, thanks to its more heat resistant O-ring.
The KTM 350 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.
The KTM 350 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.
The engine is fitted with a smooth 6-speed semi-close transmission, which features a special surface treatment on the 2nd, 3rd and 4th gears for best reliability. An advanced ´No Dirt´ gear shift lever design prevents mud and sand from blocking the joint of the lever and guarantees trouble-free shifting. All 4-stroke engines are fitted with a gear position sensor, giving the option of different engine characteristics for each gear. For 2018, the transmission shaft gets a new C4 bearing that has a bigger overlap in the case. This guarantees better reliability even at extremely tough operating conditions.
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 control unit 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 select switch.
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.
To balance the mass-forces, the KTM 350 SX-F engine uses a multifunctional balancer shaft, which at the same time drives the water pump and timing chain.
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.