The word on the moto-grapevine was: No change for the KX250F for 2010. The economy killed a revised EFI model, and we'd get the same old shootout-winning, championship-winning bike we had for 2009. Basically, grapevine fail. EFI did not appear, but the KX is the same old bike except for the piston, piston pin, cylinder, crankshaft, oil pump, much of the transmission, centercases, radiators, swingarm, steering stem, exhaust header, suspension settings and front fender. Oh, and new graphics. If you are thinking, as we are, that not much of the bike is left unchanged, then you are right. Of course, as is the norm in these times, the changes are small, but the difference is most noticeable.Of the many changes, the piston and radiator changes are most obvious to eye. Kawasaki had an all-new radiator design in 2009, and the closely-packed look of the '09 rad is gone, and a more familiar looking but larger cooler is used for the new machine. It is 10mm thicker at 32mm front to back and 4mm wider for a total of 117.8mm. The piston appears to have a narrower skirt and an upgraded machine finish in places when you see it from the top. Flip it over, though, and the works-inspired piston is very new. Instead of a pair of strengthening ribs running front to back and forming the piston pin mounting boss area, the new piston has ribs running both directions, and the pin boss area is narrower, so the piston fin is lightened via being 38.1mm long as opposed to 45.1mms. The piston is more than lighter and stronger and impersonating a works part, the top is designed for better combustion, but somehow the design of the piston is taller, so the (now Electrofusion coated) cylinder is a half millimeter taller to keep the 2009 compression ratio unchanged.Kawasaki is terming the new stainless steel header pipe as "more durable," and that does sound a better selling point that saying the titanium header was too expensive. On the plus side, the SS header is more durable, and the tapered shape is refined for more boost.One area where we haven't been thrilled with the KX is the transmission. Shifting was never great on our 2009, but changes to the dogs and shape of some gears and the elimination of a clip and spacer seems to have paid off. So far the new bike is shifting effortlessly and great with no problems picking up the next gear under a load. The cases are thicker in the engine mounting area, and that could have helped as well.Kawasaki aimed at better handling balance, better front to rear suspension balance and more useable bottom and mid power. To us it feels like they got 'r done. We only have one day on the bike at the private Castillo Ranch track. Located in the coastal hills of California, the track has several steep pulls you would think would a 250F groaning and straining, but the engine picks up from very low in the rpm range. A little more rpm and the engine snaps hard to life and jumps out of turns. It pulls strongly to the top of the power. Spin it too hard and the engine makes a characteristic rev limiter sound, and the power tapers, but leaves a little pull in case you need it for a jump take-off.Our 160-pound pro found the suspension soft, but it worked fine for others, and with none of the harshness we experienced with the 2010 KX450F. The chassis feels neutral and nimble, and very easy to tuck into tricky ruts. At the same time it never grew too busy on the soft and deep sand straights at Castillo.In a year we expected the bikes with existing designs like the KX to suffer compared to fully new EFI models, so for it doesn't seem to be the case. The 2010 KX250F feels formidable, and if anything better armed for the current class conflict than ever. We haven't had the KX on the track with other brands yet, but we'll be shocked if it isn't fighting for the lead in the class. And with all the upgrades for reliability, the bike should be a better value than ever.