Imagine the perfect motocross bike. Does it already exist? Or does it inhabit only thought, a hybrid outfitted with the best characteristics of each brand? If you’re one of those types convinced perfection has been achieved and the faultless bike is already out there-maybe even in your garage-then I’ve got some bad news. You’re either wrong-or afraid of change. Either way, we need to get you some help. So lie back on the strange-looking couch and listen carefully: The perfect bike doesn’t exist. If it did, companies wouldn’t go out of their minds redeveloping, reintroducing and reinventing perfectly competitive models. The 2006 Kawasaki KX250F is evidence of just that. It’s a bike that in just two years racked up five national championships in arenacross and supercross competition and is celebrating the capture of a fiercely competitive outdoor title by Ivan Tedesco. With these results, Kawasaki could easily sit back and fine-tune what we thought was a good machine. But it didn’t. It stood up to build a great one.If you’re the owner of a ’04 or ’05 KX250F (or Suzuki RM-Z250, for that matter), look in the garage and then look at this new baby that’s exclusively Kawasaki (no sharing with Suzuki this year). Notice anything different? You should because there’s a lot going on. It’s not merely new here or there. It’s all-new, completely changed and, more important, improved just about everywhere.The first thing you’ll probably notice is the aluminum perimeter frame that resembles, not surprisingly, the best-handling 250 four-stroke made to date. Although it seems like a big step for Kawasaki to follow Honda’s aluminum frame with one of its own, it’s not. Kawasaki has been building steel perimeter-framed motocross bikes since 1990 (longer than anyone) and has a boatload of experience building aluminum perimeter frames in its street bikes.It’s this experience that results in a chassis design lighter than the ’05 model (a claimed 2.2 pounds), which has the sole assignment to deliver superior handling characteristics with an emphasis on power-to-the-ground traction. How does it work? Great. But more on that later. There’s more new stuff.The next big thing Kawasaki threw into its championship-winning bike was Showa suspension. Yep, Showa. Another similarity shared with the KX-F’s red-blooded rival. The Showa twin-chamber fork replaces the lackluster unit on last year’s bike and might just solve the biggest reason the green bike hasn’t won our shootout. Other than the Showa component bolted on up front, Kawasaki’s all-new chassis design also includes a radically new linkage-mounted to the bottom of the unpainted swingarm-and a Showa rear shock utilizing high- and low-speed damping. How does it handle? Great. But more on that later. There’s still more new stuff.Notice the radiator shrouds. Kawasaki is back in black for ’06 with a two-piece cover that goes minimalist graphically and high-tech functionally. Kawasaki engineers claim the two-piece shrouds are designed to fit around the new aluminum frame, with the lower section (green) angled in for more clearance and a slimmer feel to the new chassis. Other plastic updates include holes in the sidepanels for more flow to the filter and even larger holes in the upper shrouds, next to the gas tank, to increase airflow through the radiators.Speaking of radiators, there are big changes in this important department as well. The new Denso units aboard the ’06 KX250F are thinner, have tighter spacing on the cores and sport a new fin design compared to the ’05 model’s. All this means improved cooling with less bulk. Kawasaki also included new radiator hose sizes and routing paths engineered to better balance the flow between the two cans.Other visual changes to the ’06 come from the trick-looking triple clamps, with available 111/48-inch mounts for an oversize bar, smoother hubs front and rear, petal-style front and rear disc brake rotors, a Renthal aluminum bar, new grips and four less spokes on the rear wheel. Yep, exactly four.Now for the stuff you can feel at the wrist.Inside the engine Kawasaki revised the intake and exhaust ports as well as the combustion chamber to beef up the low to mid-rpm pull. It also concentrated on top-end boost by increasing the compression ratio from 12.6:1 to 13.5:1 specifically to improve high-rpm performance. Stiffer valve springs were included to help keep the valves opening and closing when the throttle is tapped, and a new surface-hardened crank is used for extra rigidity. To stand the torture of high-rpm output, the piston also gets thicker crown material and oil flow has been increased by nearly 20 percent thanks to more efficient oil pumps.Even the intake is improved on the KX250F with a new airbox and intake boot shape vastly improving flow to the carb. About the only thing not touched is the pipe and muffler combo. It could literally be swapped with last year’s because it’s exactly the same (and just as loud, but more on that later. There’s still more new stuff).The power-transfer department gets some updates as well. New friction plate material and stiffer clutch springs improve the clutch feel, and heavier gear construction should keep the transmission in check with the more powerful engine.So, finally, how does all this work? Well, quite honestly, it works great.The ’06 KX250F is a superb motocross machine that takes full advantage of its own improvements. Standing out the strongest has to be the new chassis with the motor and finish improvementsfollowing closely behind. Not once did the new suspension let down any of our testers. The bike tracks straight, eats up chop, soaks up landings and corners just as well as one of the best-turning bikes in the sport: the ’06 Honda CRF450R. Showa components and aluminum perimeter frames are a great combination on two brands now.Often new frame designs put manufacturers through a learning curve. We all know Honda had its issues at first, but one ride on this Kawasaki and you’ll swear you have a fourth-generation Honda frame under you. The bike has rigidity where you need it and flexibility where you want it. It’s an excellent chassis and a home run for Kawasaki on its first at bat. Ergonomically, the bike scores again. The frame is easy to grip with ankles or knees. And the bar to footpeg ratio is spot-on for the average-sized rider. The new grips are soft and tacky, allowing you to hang on with relaxed hands. But they did seem to wear a little quicker than others. Whether we were riding the exclusive Castillo Ranch Motocross Park with its loamy, deep soil or the fast laps of Perris Raceway with its rutted corners and jump combinations, this bike handled excellently.Enginewise, the Kawasaki improves again. Although not nearly as impressive as the suspension and handling improvements, the new powerplant is substantial in the least. Plain and simple, the motor likes to be revved; the more you twist the throttle the happier it becomes. It has a very linear delivery with a high power level at all rpm that would rather work right here and now instead of screaming further into the higher revs. Typical of what we’ve come to expect from the Kawasaki four-strokes, this motor seemed tight to us. Also, when you shut the throttle off, the revs drop off quickly. With time this begins to loosen and allows the bike to rev and coast more freely. We got a bit more power by dropping to a 175 main jet, but this was during 90-degree weather.Some things we noticed, which were only slightly disconcerting, were excessive amounts of compression braking on the KX250F and a substantial amount of exhaust noise. We quickly diagnosed and solved the compression-braking issue by turning up the idle (an old four-stroke trick). But the bike’s decibel volume is a little loud when on the pipe, especially under a load. We’re curious to see how it stands up to a decibel meter and are pretty sure a good portion of the noise is coming out of the airbox.Why build a new bike from the ground up when your current model is winning championships? It’s called progression or advancement or maybe just gambling. And for ’06 Kawasaki decided that winning six championships in two years wasn’t quite enough for its 250 four-stroke, so it rolled the dice on an all-new bike. A bike it now feels is the best it has ever built.For two years now, this bike has been a fork away from winning our shootout. The ’06 model solved that problem with the addition of the Showa suspension and a functional new chassis. Just for fun, the green guys improved the power and added great brakes, too. How will it stand up in this year’s shootout? We’ll find out soon enough. Until then, everybody else better bring plenty of ammoOpinions
I wasn’t sure what to expect from Kawasaki’s first try at an aluminum frame on a motocross bike. But after a day riding the bike, I’m really surprised at how good it is. How good? Well, you don’t even notice that the bike has an aluminum frame, which is strange because for every other manufacturer that swapped materials, well, you noticed some changes, and they weren’t always 100 percent positive. There were always some trade-offs, and I’d usually spend a little time playing with the suspension to figure out the new bike. I didn’t even feel the need to fiddle on the KX-F. I set the sag and just rode. It felt as good as the CRF250R I rode last month in the chassis and handling. The motor, on the other hand, seemed very tight and a little reluctant to rev. Plus, it had a bit much compression braking. But it was powerful. Now I’m really hyped to ride the KX450F and Yamaha’s new aluminum-framed bikes.-Jimmy Lewis5’10″/175 lb/Vet ProAfter spending a lot of time riding the ’05 KX-F/RM-Z, I was stoked with all the changes on the ’06. The first thing I noticed was the aluminum frame. It felt solid but not stiff. The bike’s ergonomics were comfortable right from the start, and the Kawi never hesitated to go where I wanted it to. The motor has a lot of snap off the bottom and has good roll-on power, and I love how responsive it is all the way through the powerband. The suspension was awesome. Usually I don’t like stock settings, but the KX-F felt as if it was set just for me. The fork was very plush on big landings, and the bike was very stable on the rougher sections of the track. Brakes ruled: It stopped on a dime. Kawasaki has definitely stepped it up in the right direction with the ’06 KX250F, and I think this bike will bring home a lot more championships. -Matt Armstrong5’7″/150 lb/ProThe 2005 KX250F has been my bike of choice for most of this past year. It works well for me. The ergos fit my size and riding style the best out of all the 250 four-strokes. Plus, the power delivery allowed me to ride it more aggressively, like a 125 two-stroke. From the first few laps on the ’06 KX250F I noticed the bike didn’t really change the things I liked about the ’05 KX-F but repaired all the things I didn’t like. The most noticeable difference in the two bikes for me was suspension. The new bike felt really good through small chatter bumps that were a huge issue for the ’05 model and soaked up most of the big bumps and landings. I felt I could corner much better and brake harder on the ’06. The only thing I could really pick on about the new KX250F is how loud it seemed. All in all, I really think the bike is going to be a strong contender this year. -Joe McKimmy
5’9″/155 lb/NoviceWhat’s New
* New aluminum perimeter frame featuring composite construction of forged, extruded and cast aluminum.
* Showa’s twin-chamber fork separates air and oil for stable damping through long motos.
* Showa rear shock.
* New linkage designed to transfer power in a forward direction, not up and down.
* New unpainted aluminum swingarm.
* Petal disc brakes offer lighter weight, better feel and more efficient braking performance by cleaning brake pads.
* New cooling system with higher capacity, thinner radiators featuring tightly packed cores and new fin designs.
* Revised coolant-line routing to balance coolant delivery to each radiator.
* Revised intake and exhaust ports for better low to mid engine response.
* New cam profiles and stiffer valve springs for increased high-rpm performance and reliability.
* Increased compression ratio from 12.6:1 to 13.5:1 for increased high-rpm performance.
* New intake design for less restrictive flow.What’s Hot
* Showa suspension front and rear just might be what this bike needs to be the class leader. It now turns better, reacts faster and goes straighter than ever before.
* New linkage and rear suspension geometry put power to the ground to push the bike forward with great traction.
* It starts so easily! Like butter, even when hot.
* You can’t tell you’re riding an aluminum-framed bike.
* Smooth, linear power.
* Optional top handlebar clamps available for oversize bars.
* This bike sounds loud. It’s the only area we can’t see an improvement over last year, unless black isn’t your color.
* Does black plastic show scratches easier?Specifications
Claimed dry weight: 204 lb
Actual weight (ready to ride, no gas): 217 lb
Seat height: 37.5 in.
Fuel capacity: 1.9 gal.