After having presented the older sister of Kawasaki motocross, the KX450F 2012, Now speak of the “little sister” smallest 250, the KX250F. The most important is the adoption of two injectors instead of one that give more power to the engine at high revs. For this model, then there are major suspension modifications. We shall now analyze the motion point by point.
The single-cylinder 4-stroke liquid-cooled 249 cm3 is designed to prefer the performance at high speed. Well known for its high efficiency and power output (thanks to the development and parts style racing department, as the piston high performance with bottom-bridged box), the KX250F 2012 model exceeds the performance of the engine through MX injection plant with two primers ever installed on this type of motion. The more power – Perceived by riders of any level – is complemented by the response of the fluid injection Model 2011. Further modifications to the engine offer more fluidity in the exchange rate and high reliability.
The double injectors give the “Verdon” a power greater than any of the engine. The feeling of the couple brings to mind the engine with carburetor, while the excellent response to the injection remains unchanged. A primer is downstream of the throttle (The position of primers in standard equipment), and a second primer located near the upper hand all’airbox. Unlike the two injector systems typical supersport models (where the upper injector comes into play only when necessary, providing additional fuel), in this case the two injectors perform distinct functions: the lower guarantees a smooth and immediate response, while the higher education has the task of supplying power. With increasing engine speed and throttle position, injector operation goes lower to the upper. Depending on which is grafted a low gear (1st, 2nd) or high (3rd, 4th, 5th), the transition is gradual and almost instantaneous.
The greater distance between the injector and the upper chamber not only extends the range of mixing between the particles of fuel and the intake air, but at the same time allows the mixture to cool before entering the combustion chamber, improving thereby filling. To ensure that the sudden demand for a high flow of fuel by the engine at higher rpm, both injectors are fitted with holes larger than those used in the KX450F. Although the upper injector is equipped with a smaller body, both injectors are spraying with 4 holes and ultra-fine spray particles of the size of 120 microns. The fuel flow is therefore about 20% higher than the KX450F.
The throttle body 43 mm using a command sequence to provide a flow of air similar to a FCR carburetor. Using two interconnected levers, the throttle body opens more quickly after reaching the open position 3 / 8, providing an excellent response in terms of responsiveness and power.
Designed specifically for motocross, the fuel injection system incorporates a ECU lightweight and compact and requires no battery, with a view to further reduction of weight. With the injection of fuel is also no need for finalization of the engine running and the weather of the track.
The ECU, compact and lightweight, located in front of the steering head (behind the number plate), was designed specifically for motocross. To cope with stress and vibration typical of this use, the fuel pump relay is built into the ECU. In the 2012 model, the ECU is slightly wider so as to allow control of the two primers.
The fuel pump, located in the fuel tank is aluminum alloy and to ensure a constant flow of fuel even in the most extreme operating conditions dictated by the style of motocross, the fuel pump was fitted with a lid to the plastic filter integrated surrounds the inlet of the fuel and acts as well.
The set-injection kit (optional) is the same one used by the Kawasaki team in Europe and the United States. The kit allows experienced pilots to adjust the characteristics of the engine, by rewriting the data mapping, according to individual needs, and also to record driving data and then analyze them to proceed further developed. The kit contains injection setting KX Racing Software, the controller of the ECU, the mounting bracket, cabling and USB cable. In addition to the kit, you need only a PC and a 12V battery.
The following changes to the transmission and exchange of the group contribute to a smoother transmission. The new drum gear reduces the distance of insertion of the march by the shift fork (5.3 mm> 5.0 mm), resulting in smoother gear changes. The reduced surface roughness (6.3 ?mRy>> ?mRy 3.2) of the connecting rods of the change allows a more uniform movement of the forks of the change. The connecting rods are also full and not empty, thus contributing to increase its durability.
The engine has been developed so that the torque curve follows the limit of adhesion as long as possible. Considerable efforts to expand the possible range of the pair, so as to maximize traction in a range of engine speeds widely as possible. The piston high-performance recalls the design of our race bikes and provides better performance at any engine speed. A small coat, stiffening ribs and the introduction, only in mass production, a piston-back double girder, resulting in a lighter and more durable piston.
The cylinder is covered in Nikasil, The slight titanium valves (Intake: 31 mm Exhaust: 25 mm) reduce the reciprocating mass and ensure reliability at high speeds. The valves have an ultralight rod extremely thin, like those used in supersport engine. The intake valves are more often the fungus to increase strength and are made of titanium with a very rigid, like the exhaust valves.
The thicker crank and the superior strength of the axis of coupling contribute to increased reliability. These changes increase the moment of inertia (2 kg cm2), but are offset by a reduced time with revised flywheel (less than 1 kg cm2). The moment of inertia is a total of more than 1 kg cm2. The design of these elements increases the moment of raising the compensation factor balancing of the crankshaft. A nearly 60%, the balancing factor of the KX250F 2012 model equals that of our race bikes. The balancing factor contributes to the high reduction of engine vibrations, a smoother power delivery and improved performance schemes medium-high.
More often, the stem of the connecting rod, which contributes to greater reliability of the component and the pad.
With a thickness of 32 mm, a width of 117.8 mm and a large step between fins and tube, new radiators have the same resistance to accumulation of mud and cooling performance. The strength of the radiators has eliminated the support brackets and reduce the overall weight.
The head of the chain drive sprocket helps to stabilize the effect of engine braking by reducing the backlash generated by the sudden release, and the sudden recovery of the game in the lower part of the chain. This additional control facilitates the entry into the curve.
The aluminum frame of the KX250F is a lightweight and slim composed of parts forged, extruded and cast. Balancing and calibration of the frame were performed according to the needs of riders from the race. Appreciated for its stability at high speeds, the chassis is supported by the fork SFF (Separate Function Front Fork) already on the 2011 model, characterized by a significant reduction in friction, which ensures greater driving comfort and improved shock absorber action. In the model 2012, with the changes to the suspension resulting in greater strength, superior resistance to the maximum speed of the front fork and rear suspension feel more stable.
In new Uni-Trak rear suspension the leverage of the suspension are lower than under the arm, so as to lengthen the travel of the suspension. The elongation of the race can, in turn, more accurate adjustment of the suspension.
The rear shocks stiffer spring (k = 51 N / mm>> k = 53 N / mm) and the new calibration of shock absorbing fluid and determine an action that provides a constant feeling of greater stability and greater flexibility in ‘ structure. The compression of the new double adjustable shock absorber, allowing you to tune the damping action at high speed and low speed separately. The rear shock also features a Kashima coating on the cylinder tank. Reducing friction makes it more fluid action of the suspension.
Among the various components of the racing department style stand KX250F disc brakes front and rear petal. In addition to reducing the weight of the unsprung weight, the wave shapes of the petal discs help to keep clean the brake pads for more efficient braking action.
The rear parapinza protects the caliper from damage. Renthal aluminum handlebars (standard) style racing division is standard. The rear hub bearings without ribs and spokes reduce unsprung weight. The wheels are finished in black alumite1 (black), just like our race bikes. The fork and rear shock registers have finished alumite1 blue (blue), as bike racing in the United States.
The graphics are based on those in competition, particularly dynamic.
