The pressure the cast crankcase has been designed with significantly reduced wall thicknesses compared to cases produced by gravity die cast. The aluminum alloy utilized has great tensile strength while ensuring high resilience against stone-chipping and other damage.
The 250 XCF-W's crankshaft has a flywheel that is designed to achieve optimum traction. The crankshaft employs a plain big end bearing. Two force-fitted bearing shells run directly on the crank pin. The necessary oil feed for this bearing is ensured by the engine's pressure lubrication. This design increases the engine's long-term durability and lengthens crankshaft service intervals, which is a customer benefit in terms of time, effort and cost.
Cylinder & piston
The short stroke and large bore allow the use of large valves. The lightweight, forged bridged box-type piston guarantees optimum performance and a dynamic power delivery, while the low oscillating mass reduces vibration.
The centerpiece of the DOHC engine is its cylinder head with two overhead camshafts and DLC coated followers. The large, flow optimized ports in combination with large intake valves ensure a high flow rate, which in turn provides significant performance. The camshafts have been designed to achieve maximum power and torque figures while maintaining an off-road specific power delivery.
The one-piece basket of the DDS clutch (damped diaphragm steel) is machined from solid high-tensile steel in one solid part together with the primary drive gear. This process guarantees unbeatable reliability and, together with the thin steel linings, contributes to the narrow engine width due to a compact rivet-less design. The diaphragm spring makes it possible to implement an additional rubber damping system inside the clutch hub, ensuring reliability for the transmission and excellent traction. Finally, the hydraulic clutch mechanism by Brembo in conjunction with the diaphragm spring provides a very light clutch operation and controllable modulation.
Engine Management System (EMS)
The Engine Management System by Keihin with electronic fuel injection via a 42mm throttle body ensures a snappy response and maximum engine performance. An oil-cooled 196 W alternator provides sufficient energy for the fuel injection, lighting and other electrical loads. With an optional map-select switch from the Power Parts program, the EMS can allow the rider to select different engine characteristics. In addition, the optional User-Setting-Tool provides the ability to readout engine data with a laptop and change the ignition and injection mapping with just a few mouse clicks.
The 250 XCF-W engine can be started with a kick starter as well as an electric starter. Well protected behind the cylinder, the electric starter is connected to the starter freewheel on the ignition rotor via the starter drive in the ignition cover.
Specifically developed for the 250 XCF-W, the 6-speed off-road gearbox has relatively short gears from 1st to 5thand an overdrive 6th gear. The transmission is distinguished by easy and precise shifting.
The crankshaft drives an intermediate multifunctional shaft, which in turn drives the coolant pump and the two camshafts via the cam chain, while also acting as a counter balancer. A hydraulic tensioner ensures reliable chain tension to achieve highly precise valve timings.