01. Engine & Exhaust
The KTM 350 SX-F's 349 cc engine is an anomaly in the world dominated by 450 cc 4-strokes - but don't let that fool you. This neatly arranged, compact and lightweight powerhouse has been a contender over 2 decades. It features an innovative clutch system, perfectly geared transmission, and a lightweight DOHC cylinder head, which all contribute to making it an extremely impressive engine. Fitted with the latest electronic fuel injection system and a useful electric starter, just one push of a button fires up this impressively competitive engine.
Boasting two overhead camshafts with friction-optimized super-fine surfaces, the cylinder head on the KTM 350 SX-F is the Ace up its sleeve. Lightweight titanium valves (intake 36.3 mm, exhaust 29.1 mm), a maximized flow rate, and the optimal power band mean outstanding performance across the entire 13,400 rpm range.
The KTM 350 SX-F's crankshaft features an ultra-stiff design and utilizes a short, lightweight connecting rod, contributing to the incredibly dynamic and efficient power delivery. The big end bearing features two force-fitted bearing shells, which run directly on the crank pin. This design is a prerequisite for the extremely high engine speed levels and the unrivaled power of the 350 cc. The 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 KTM 350 SX-F boasts compact, lightweight engine cases which are manufactured using a high-pressure die-cast production process. This helps in reducing weight while retaining strength and durability. The design also allows for optimal shaft arrangements close to the center of gravity, resulting in better mass centralization and rideability. Most importantly, however, the engine covers feature a smart surface structure that reduces the wear caused by the rider's boots, keeping them looking as fresh as the day the bike rolled off the production line.
The KTM 350 SX-F is fitted with a robust 5-speed transmission, with gear ratios 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.
Engine management system
The state-of-the-art KEIHIN Engine Management System, with electronic fuel injection, features a 44 mm throttle body. The injector position guarantees optimal atomization of the fuel and air on the way to the combustion chamber, resulting in instant response and maximum performance when opening the throttle.
Cylinder and piston
Inside the 88 mm bore cylinder is a lightweight, forged, bridged, box-type CP piston. It features an extremely rigid structure and a unique crown shape to suit the high-compression combustion chamber with a ratio of 14.2:1.
To balance the mass forces the KTM 350 SX-F's engine produces, it's fitted with a multifunctional counter-balance shaft, which effectively reduces vibration, while driving the water pump and timing chain. Now that's multitasking.
The KTM 350 SX-F's diaphragm steel clutch literally puts the control back in your hand. It features a durable, one-piece clutch basket and primary gear, made of high-strength billet steel, guaranteeing unbeatable reliability. It is fitted with extremely heat-resistant steel carrier friction discs, which are pre-tensioned by means of a diaphragm spring, ensuring the most effective disengagement of the clutch. This design substantially reduces the operating force required to pull the clutch and is made even easier with the BREMBO hydraulic system.
The standard electric starter on the KTM 350 SX-F uses a proven starter drive and a strong starter motor made by Mitsuba. It provides quick and reliable starting, saving you precious time and energy when you need it most, always ensuring the strongest possible race finish.
Handlebar map select switch
The KTM 350 SX-F brings technology to the track in the form of a multifunctional handlebar map switch. This allows riders to select traction control, launch control, and alternative power curves. The TRACTION CONTROL function is a unique feature that guarantees more efficient traction and better control when accelerating the bike off the line, or in track condition which calls for refined power output. LAUNCH CONTROL ensures the most effective launch out of the gate, by balancing the optimal levels of power and traction, while the engine mapping switch allows riders to select an alternative power map other than the standard configuration, providing performance options during the race.
Keeping things cool when the going gets heated, is a set of radiators ideally positioned for a lower center of gravity. By using computational fluid dynamics technology together with a clever coolant circuit routing, the innovative system ensures the optimum engine temperature for the highest performance, no matter what the conditions.
When it comes to power delivery and performance, the exhausts on all KTM 4-stroke SX-F models play a key role in getting to the head of the pack. Featuring a model-specific header pipe with an advanced Flow Design Header, the design allows the exhaust to be disassembled without removing the shock absorber. The aluminum sleeve, end cap, and internal design of the silencer allow for slimmer ergonomics, making the bike feel slimmer without any compromise to regulatory noise limits.