01. Engine & Exhaust
Compact dimensions with class-leading power output, the KTM 250 EXC-F's fuel-injected DOHC engine is the most powerful and refined 250 cc on the market. Its efficient power delivery is available throughout the entire rev range and with its low weight of only 27.9 kg, this engine is the lightest and most competitive powerplant out there. With Euro IV homologation, it's not only considerately green, but leaves the competition green with envy too.
The KTM 250 EXC-F engine is fitted with a compact DOHC cylinder head for optimal mass centralization while contributing to even better handling. The head configuration, with double overhead camshafts controlling the gas flow through the ports, promises outstanding, enduro-specific engine characteristics. The DLC coated finger followers, as well as the lightweight titanium valves they actuate (intake 32.5mm, exhaust 26.5mm), allow for higher engine speeds, a crucial factor in the 250's class-leading performance.
The KTM 250 EXC-F's crankshaft is located in an ideal position close to the center of gravity, contributing to easier handling. It 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 engine's pressurized lubrication system provides the necessary oil feed for this bearing. This design has a direct benefit for the crankshaft with extended service intervals, which are lengthened due to the plain bearing. So just pin it, all day long.
Crankcases and engine covers
The compact engine cases are manufactured using a high pressure die-cast production process which helps with weight reduction, while retaining strength and durability. The design allows for a very centralized shaft configuration, making the engine very short and compact, while contributing to an efficient centralization of mass. Additionally, the engine covers feature a smart surface structure which reduces wear caused by the rider's boots, keeping them looking as fresh as the day you bought it.
The KTM 250 EXC-F features a robust 6-speed transmission made by PANKL Racing Systems. The gears are made of a strong, forged raw material, ensuring the highest durability and reliability level. There was no need to change the gear ratios that are perfectly matched to the power characteristics of the engine. All four-stroke engines are fitted with a gear sensor, giving the option of different engine characteristics for each gear.
Engine management system
The state-of-the-art Keihin Engine Management System, with electronic fuel injection, features a 42 mm throttle body with separate systems for cold starting and idle adjustment. The throttle cable mount allows for easy access and a smooth routing of the cables. The ECU features selectable engine maps which are optimized to the exhaust, airbox and engine configuration, regulating the unique traction control and are activated by the handlebar map-select switch. It also provides different maps for each gear, according to the information received from the gear sensor, ensuring maximum power as you shift through the gears.
Cylinder and piston
Inside the short 78 mm bore cylinder, is an extremely lightweight, forged bridged box-type piston made by CP. The piston features a unique crown shape that has been adapted to the combustion chamber. Despite its incredibly low weight, it has an extra rigid structure for enhanced durability. Thanks to its lightweight construction, the oscillating masses are low, giving the engine extremely lively characteristics. The compression ratio of 13.8:1 delivers an exceptional engine performance and reduces the risk of engine knocking.
The multifunctional side-mounted counter balance shaft masterfully balances all the oscillating forces, while also driving the water pump. It effectively keeps engine vibrations to a minimum, resulting in the smoothest ride even at the highest engine speeds.
The KTM 250 EXC-F is fitted with the extremely durable, KTM-developed DS clutch (diaphragm steel), with a wear-free steel basket and heat resistant clutch plates. It uses a diaphragm spring instead of the usual coil springs, which results in considerably easier clutch action. Additionally, the Brembo hydraulic system provides easy and precise clutch modulation throughout the entire operating temperature range.
The standard electric starter on the KTM 250 EXC-F uses a proven starter drive and a strong starter motor made by Mitsuba. As demonstrated time and time again, it provides quick and reliable starting, saving you precious time and energy when you need it most.
Maintaining the optimal engine temperature is crucial to ensuring consistent horsepower throughout the ride. The KTM 250 EXC-F features radiators which are mounted close to the center of gravity and match the design of the shrouds perfectly, in order to achieve perfect ergonomics. By using CFD technology (Computational Fluid Dynamics) and a smart coolant circuit routing, the innovative system ensures optimum engine temperature for the highest performance, in all conditions. Above all, the delta distributor, integrated into the frame triangle, features a large center tube, making the coolant flow from the cylinder head to the radiators highly efficient. The radiators have special protectors that protect from flying rocks and debris while also acting as a brace to disperse energy around the radiators in the event of an impact.
When it comes to power delivery and performance, the exhaust plays a key role and packs a punch that is hard to beat. All 4-stroke EXC models feature two-piece header pipes which can be disassembled easily and allow easy access to the shock. The aluminum muffler sleeve has a short and compact profile, bringing the weight closer to the center of gravity for better mass centralization.