Kawasaki recently invited Cycle News to one of our favorite tracks in California, Zaca Station, to ride the company's new 2013 KX450F.
Last year, the KX won our 450 motocross shootout and a lot of that was because of its stellar overall performance on the track. But what really did it for us was the KX's adjustability. The handlebars have multiple positions, the footpegs can be lowered from stock, mapping can easily be altered (via three pre-programmed couplers), and the KX featured (for the first time on any production motocrosser) launch-control mode to give you two power-delivery setting to chose from for the starts. For 2013, the KX450F is even more adjustable thanks to a new Kayaba PSF (Pneumatic Spring Fork) air fork and an updated shock.
Technically, the new air fork isn't really any more adjustable than a traditional spring fork but it is far easier, quicker and less-expensive to adjust when it comes to "spring" rates. Want the fork to be a little stiffer after riding morning practice? No problem, add a few pounds of air (two pounds equal about one spring rate) and you're ready for the first moto. Try that with spring forks, assuming you don't have you're own personal mechanic.
Air forks also have other advantages over spring forks. They're also lighter, since the steel springs have been replaced by lightweight air, and there are no more minute metal shavings from the springs to contaminate the oil, and the internals can be made larger for improved fork action.
And to further increase the KX's overall adjustability, the shock's rebound adjuster now has 33 detents instead of 22.
One of the highlights of the 2013 KX450F is its new PSF (air) fork. Photography By: Kinney Jones
Kawasaki also made a few other changes to the 2013 KX450F. The swingarm is 20mm longer to improve torsional rigidity, thus improving traction and handling, and the motor has revised ECU settings, and changes have been made to the intake cam and piston. Like the 2013 KX250F we recently reviewed, the 450 has silver instead of black-colored engine covers to better hide scratches and wear, the grips are new and longer, the front-brake master cylinder has been modified, and subtle changes have been made to the plastic and graphics. The front number plate and front fender are reshaped, and the rear fender is now white.
When we rode the bike for the first time, we were most curious about the new fork, and our testers were definitely impressed.
"The fork works excellent," said Cycle New chief test rider Jason Abbott, who now has nearly seven hours on the bike. "Not only do they weigh 1.7 pounds less than the previous fork, which definitely improves the overall front-end feel and maneuverability, but it also just plain feels better - as far as action. The initial stroke is very plush and works well through the smaller chop and braking bumps, which gives you more control and confidence while entering corners.
"Mid-stroke is super solid," he added. "It worked well over the entire track and never deflected or had any type of spike when the track got rough. Bottoming resistance was also excellent, especially when landing in holes and onto any other unfriendly obstacle.
There's plenty of power under the hood, so to speak, and it's all useable. Photography By: Kinney Jones
"Adjusting the air fork is one of the things we played with a lot while at Zaca Station; after all, when they're that easy to adjust, why not? Now you can really work on getting them finely tuned.
"Initially, with the stock 35 psi in the fork, we found on the downhill sections the front end to dive just a bit under hard braking. So instead of changing the clickers and tighten up the valving, we simply added +2psi to the fork, which is equivalent to +1 spring rate, and the front-end dive was all-but eliminated, giving me what I felt was more control on the downhills while still keeping the same plush handling all the way around the track."
Abbott was impressed with the rear end, as well.
"The new swingarm has larger front casting, which Kawasaki says is designed to increase rigidity and reduce the amount of flex a rider would feel while exiting corners - the change, I found, is subtle but noticeable. I felt you gained a bit more overall control over the bike with a little less rear-end wandering."
Abbott was a big fan of last year's motor and still is.
"This bike rips! Its one of the most manageable yet powerful 450 motors out there. Throttle response is instant and the Kawasaki's FI system is spot on. Bottom-end is strong and definitely has a good amount of torque, but, again, the motor is super-easy to manage, which definitely helps you get in and out of the corners smoother and quicker.
"Overall, the power pulls off the bottom into a strong and real long mid-top pull. It has such a long and broad power curve that you're able to find power anywhere, anytime.
Kawasaki knows that by making the KX more adjustable it will fit more people. Photography By: Kinney Jones
"The mapping couplers are something we played around with quite a bit at Zaca. The stock coupler works quite well, but I still tried the hard-packed plug - for hard-pack terrain - and this one definitely mellowed out the power delivery quite a bit, which helped in the slippery corners but overall wasn't the plug for the hilly Zaca track, it mellowed it out too much and made the bike feel a little sluggish.
"Next, I tried the soft-terrain plug for a more aggressive power delivery and this one was fun. The motor was freer-revving and quite aggressive, just as advertised. I definitely liked this plug and the harder-hitting power it delivered, but when the track got rough, the harder-hitting delivery, I must admit, wore me out a little quicker. I'll save this one for freshly tilled and prepped tracks.
"Finally, we modified one of the couplers to my own spec via Kawasaki's tuning tool. I wanted to smooth out the bottom-end even more than the original coupler while still keeping the long, mid and top pull I like so much. Ah, the beauty of EFI. It's kind of like changing out pipes without the hassle or cost.
"I'm addicted to the launch-control mode. If you're a racer, I feel its almost like cheating, so I'm glad Kawasaki is sticking with it."
At the end of the day - well, two days, actually - there are many things that stood out about the 2013 KX450F, such as the new grips. They are definitely a welcomed addition, but they are a still a bit thin. The new rear-brake disc now matches the front, keeping the bike looking tight, and the retuned front-brake is noticeably stronger. The front number plate and fender look more aggressive, and the overall styling can be summed up in one word, factory! From the new white rear tail section, like RV2, to the blue-anodized accessories, the KX not only performs well but looks the part, too.
Overall our CN testers were impressed after their first ride on the bike. Like the '12 KX, they loved the bike's adjustability, the improved fork and still-potent and slightly massaged motor. Although we haven't come to any final conclusions about the new KX - that'll come after we visit more tracks and put more time on the bike, which will include comparisons - but we can tell you now that it's not going to be easy for any of the other manufacturers to knock the KX off the CN Shootout throne.