As our eyes scoured the 2010 KX250F looking for EFI, our orbs blew right past the myriad of changes the bike did receive. Part of that oversight can be blamed on a rumor mill that claimed the bike was unchanged, and the rest we’ll chalk up to the fact that most of the changes are all but invisible to the naked eye. Basically this is a much-polished version of the same shootout-winning, championship-winning bike we had for 2009. And while EFI did not appear, the carburetion and starting were as perfect as a carb can be.
The list of changed or revised parts include the piston, piston pin, cylinder, crankshaft, connecting rod, oil pump, much of the transmission, centercases, radiators, swingarm, steering stem, exhaust header, suspension settings, rims and front fender. Oh, and new graphics. If you’re 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 the most obvious to the eye (when removed from the bike). 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. The pin boss area is narrower, so the piston pin is lightened via being 38.1mm long as opposed to 45.1mm. 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 better than 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 seem to have paid off. So far the new bike is shifting effortlessly with no problems picking up the next gear under a load. The cases are thicker at the engine mounting area, and that could be helping as well.
Kawasaki aimed at better handling balance, better front to rear suspension balance and more usable bottom and mid power. To us it feels like they got ‘er done. Our first day on the bike was at the private Castillo Ranch track. Located in the coastal hills of California, the track has several steep pulls you’d think would have 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 takeoff.
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 or the rougher and more demanding straights and jumps at our more familiar Racetown 395.In a year we expected the bikes with existing designs like the KX to suffer compared to fully new EFI models, so far 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.Specifications: 2010 Kawasaki KX250F
Claimed Dry Weight: 231 lb
Actual Weight (ready to ride, no fuel): 232 lb
Seat Height: 36.8 in.
Seat-to-Footpeg Distance: 20.7 in.
Footpeg Height: 16.1 in.
Sound Test: 96.0 dbWhat’s hot!
Super-snappy power from low in the rpm range
Plush, balanced suspension
Light and nimble yet stable chassis feelWhat’s not!
Hits rev-limiter a bit quickly.
All the black may be fashionable, but it scratches up and gets dull early along with the rest of the bike.
|Fuel Screw (turns out):||2.2||Stk|
Other Notes: Jetting was perfect, so we never changed it.
|Fork — Compression:||10||9|
|Shock — Low-spd. Comp.:||11||Stk|
Modifications We’d Like To Try: Quieter pipe that wouldn’t hit the rev-limiter so hard.Opinions
Riding the 2010 KX250F feels a lot like riding the 2009 KX250F: a strong motor that pulls hard from bottom to mid with very good pulling power up top. Shifting under load or up a hill was not a problem for this bike. The power didn’t fall off at the second-to-third gear change, and both gears could be used very well. Gearing seemed to be close for the fast and open Castillo Ranch track. The suspension seemed a little soft for my liking. Through G-outs or on sharper jump faces the shock seemed to blow through the stroke quite badly. We turned the high-speed compression up (stiffer) so it raised the back end a bit, and that helped. The fork was soft but managed heavy braking and jumps better than the shock; it didn’t bottom or have a harsh feel at all. Overall, the bike feels comfortable and has a good motor-which is key in the 250 class. You could hop on this bike right away and go fast because it handles great in a straight line, but it can also corner well. Like I said, the ’09 was a great bike and the 2010 bike feels almost like its older, more sophisticated brother.
Having spent this season aboard our 2009 KX250F Long Haul bike, it came as no surprise that I immediately felt comfortable aboard the 2010 model. However, what did surprise me was the fact that Kawasaki was able to take a proven shootout winner and improve it-without the use of fuel injection! I was slightly bummed when I found out that the new KX250F wouldn’t be equipped with EFI, but this ends up being a nonissue on the track. The bike starts easily and the carburetion is dead-on, with a crisp, clean pull throughout all the gears. The Kawi has a pretty noticeable hit on the bottom that could stand to be smoothed out a touch, but for heavier riders and those seeking a more aggressive engine character the power spread is outstanding. Plus, you can short-shift and rev this bike without penalty. Thanks to the beefed-up transmission, I’ve yet to see any hint of the shifting issues that we had with last year’s model. The new fork is pretty sweet as well, and in stock (read: just broken in) form it was plenty stiff for my weight and speed. I’d need to spend a bit more time with the bike to completely dial in my personal settings, but I’d race the stock setup in a heartbeat, and could be happy doing so all year. So far, my gripes are limited to the same superficial criticism as last year: This bike looks hammered fast. Beyond that, I think it’s safe to say that the rest of the 250F class has a serious threat on their hands in the 2010 Kawasaki.