Kawasaki's KX250F dirt racer has been tweaked for 2012 with dual fuel-injectors - the first on a production motocrosser, says Kawasaki, a new engine control unit and a revised fuel pump to deal with the system's demands.
The KX250F's injectors play separate roles: the downstream spritzer produces smooth, instant throttle response while the upstream one, mounted nearer the airbox, dishes up extra fuel when revs and throttle position prescribe a richer mixture, much like an old-fashioned "pumper" carb, but a lot more precise.
To meet this high-revving engine's demands, both injectors have larger apertures than those of the KX450F, with a fuel-flow rate about 20 percent greater than that of the bigger bike.
There's also an optional fuel-injection calibration kit, as used by Kawasaki works riders in Europe and the USA, enabling expert riders to rewrite data maps and adjust engine characteristics to suit prevailing circumstances, and record downloadable data for analysis after test sessions or races.
Further engine upgrades include tin plating and striation on the piston to reduce friction, a nickel-plated cylinder bore, a beefed-up crankshaft web with a stronger crankpin, offset by a new, lighter, magneto rotor to compensate for the increased inertia, and a thicker connecting rod to deal with the extra grunt.
The transmission has also been revised to allow for slicker gear-changes. A revised shift drum reduces selector-fork travel from 5.3 to 5mm and the shift rods are now solid, instead of hollow, for better durability. They're also smoother, so the selectors can move more freely.
The KX250F's aluminium perimeter frame has been revised to reduce squat under acceleration, while the suspension linkage is now below the swinging arm to allow a longer suspension stroke with more tuning options. The tie rods are less rigid for a smooth action with good bottoming resistance to improve traction, the spring is stiffer and the damping internals have been revised for increased flexibility in settings.
The Showa separate-function front forks, with the damper on the left and the spring on the right, gain a stiffer main spring and a longer, softer top-out spring to reduce "clanging" when the front wheel leaves the ground.
The seat has also been revised, with new urethane filling that retains its original shape and firmness for longer. Graphics are new and the oil filler cap, the two engine access caps and front and rear suspension adjusters are now anodised blue, as they are on the US-spec factory racers.
The 2012 Kawasaki KX250F will be released in South Africa at the end of September; prices, as always, when they get here.