New bodywork and nitride-coated inner fork tubes are the first details of the 2009 Kawasaki KX250F to pique a gearhead's curiosity, but the beauty is deeper than the green and black skin. For any beauty, a long-legged skeleton is a must, and Kawasaki reshaped and sculpted every alloy bone. Every manufacturer is chasing that elusive balance of frame rigidity, flex and handling, and smaller and thinner tubes are the norm for this chassis. It is lighter, and the more-tapered swingarm is mounted higher in the frame for more traction. These changes are measured in a handful of millimeters, but small changes can pay off big. Kawasaki was aiming at better feel and traction, but a side benefit to the frame and new plastic is eased maintenance. It is vastly easier to adjust shock preload, and having the head stay moved from the top to the side of the engine will make engine work much nicer.At the heart of the chassis is a new-from-the-cases-up engine with a stronger transmission shifted by a KX450-type ratchet mechanism, a tougher valve train and a crank with a "factory level" balance factor. Major changes to the cylinder head's ports' configuration and machining process are aimed at increased performance.You don't even have to ride the bike to feel that this is a new bike. The low-rider, sit-in-the-bike feel is gone, and the riding position is more natural for riders of any stature. As soon as you start riding, you notice the bike feels much lighter than the claims about it, and the ease of control during corner transitions and in the air is striking. In addition to feeling lighter and more precise entering turns, the '09 is happier and more relaxed in ruts and is less prone to walk the front wheel up and out. As you get more comfortable railing turns on the KX, it is natural to tuck your leg up out of the way, and you get through easily on the '09 whereas you could catch a foot more readily on the '08.The changes to the swingarm and shock-made for traction and control-hit the target as well. The KX hooks up and drives hard out of turns and is more composed on off-camber exits. Even the fastest riders were happy with the stock shock setup and opted for only preload and high-speed compression adjustments. The initial testing was at the semi-private Rynoland track, and the combination of packed SX obstacles and steep, sandy natural terrain was a good test of the suspension range. Even with the load of steep sand-whoop descents, we only added a couple of clicks of compression for pro Ryan Orr. Later testing on the packed and sticky full-traction clay at Piru MX required little further adjustment. The action is smooth and well-enough controlled. At times the front feels just a bit busy coming into choppy turns at speed, but it never deteriorates to a full-blown headshake. If that is the price for the precise and accurate steering, we'll pay it.A new engine is a big investment so it had better pay dividends, and this one does. From low in the rpm range-where the '08 was eternally finicky and not clean-the KX pulls strongly without much clutch and with plenty of energy. Because of this boost down low some riders entered turns with one less downshift than with other 250Fs. At the top of the rpm range the KX pulls harder and longer, with little tendency to go flat. The engine does have a different sound now when screamed hard, but the power never hits a hard sign-off. Between the meat at the bottom and the scream at the top the energy available is smooth and somewhat like the '08. It is possible to shift just wrong and drop right into the conservative midrange power zone. For riders who have a style that consistently picks up the next gear at this rpm, the engine feels like it demands being in the perfect gear. For most, though, the engine is more powerful anyplace on the track, yet requires less thought to keep it pulling with authority. At Piru the traction can make 250Fs work to get out of uphill turns, but the '09 KX storms out and pulls strongly from gear to gear-even up the steep hills.Before the '09 KX250F arrived we were anxious to ride it, since it is the most changed machine in the class. Now that we have tested it, we are relentlessly curious about how it will hold up under the scrutiny of a full shootout, but we know this for sure: The competition had better bring its "A" game. Kawasaki has.