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Racer X Tested: The 2007 Kawasaki KX450F

The 2007 Kawasaki KX450F

In its first year, the 2006 Kawasaki KX450F won the AMA World Supercross GP title, the BooKoo Arenacross title, and the Racer X Tested online shootout; not a bad start for a completely new bike. You might think that after a year like that, Kawasaki would throw on some sweet new graphics and call it a year for 2007. Instead, they utilized the knowledge gained from a year of racing the bike, as well as the perpetual R&D that goes on behind the scenes, and improved a bike that was already at the head of the class.

There are over fifty changes to the 2007 KX450F from last year’s model. The engine gets new high-acceleration cams for quicker revs, revised ignition timing, and low-friction coating on the piston skirt, all aimed at improving the bike's low end and throttle response without compromising the top-end power. The air-filter screen has been redesigned to allow better air flow, aiding the throttle response as well. The crankshaft and connecting rod are sintered, and the exhaust-pipe header is a larger 41mm and features a tapered exhaust pipe joint to help low RPM torque. The KX450F  has a five-speed transmission this year, which is good news for everyone. First gear is slightly taller than last year, second through fourth are the same, and a fifth gear has been added. Supermoto and off-road riders are smiling. An all-new ball-bearing shift lever provides a smoother, more positive feel at the toe and works in conjunction with a new ratchet-type mechanism.

Max carves a turn on the KXF

The frame has also been revised. The twin spars are less rigid, and the frame itself is wider at the ankles and narrower at the seat, giving the bike a smaller feel without losing a good feel for the bike. An aluminum skid plate has been added, the hubs are lighter, the rear wheel has only thirty-two spokes for weight reduction, and front and rear petal disc brakes also reduce the amount of unsprung weight on the bike.

One of the most progressive changes on the new Kawasaki is the addition of a DLC coating on the front fork sliders. Factory race teams have used this exact coating for many years to harden the surface, eliminating stiction and improving the action of the front forks. Now, for the first time on a production motorcycle, the DLC coating comes standard. The forks and shock both receive updated valving for 2007.

The view was almost as good as the bike

That's just a quick overview of the changes made to the 2007 Kawasaki 450. The changes looked impressive on paper, and I was anxious to see how noticeable they were on the track. Oh yeah, the track. The track looked just as impressive. Kawasaki rented the Zaca Station track, just five miles south of Castillo Ranch. This relatively new, and private, track is a motocrosser's dream. It was built by Marc Peters and follows the big uphill and downhill contours of the dramatic landscape. If you get sick on roller coasters, this might not be the track for you. I love roller coasters. I also invited Weekend Warrior’s Max Villa up to help out with testing duties and get a fresh perspective on the bike. Max was up first, and this was his initial commentary about the KX450F:

“That thing is a handful! Man, I’m used to riding a 250F, and I can’t believe how fast this bike is. It’s literally shooting out from under me coming out of turns. The more I ride it, though, the more fun it is. It seems like it really comes ready to race. The bars are the exact bend that I use, and the grips are more comfortable than most stock grips. I don’t think the average rider would need more power than this thing has, so you definitely wouldn’t need to do anything to the motor. And with the changes to the suspension, it just feels like they stepped up the quality of the components. I don’t know if it’s just the coating on the forks or if it’s the valving changes that were made to the forks and shock, but it handles great right out of the box. I didn’t mess with the clickers at all today.”

Okay, so Max liked it.

He also likes his bars laid back, Guy Cooper-style, so I had to adjust those before I took my turn. I wasn't too excited to check the sag, so I just tightened the bars and hit the track. Max wasn’t kidding about the motor. I felt like Wile E. Coyote strapped to an Acme rocket. I could not believe how much torque and sheer horsepower this thing had. It is a tractable, usable power like most four-strokes, but it pulls much harder and longer than you expect it to.

Jeff Emig was in the house, and he smelled terrific

Before long, Jeff Emig had pulled onto the track behind me. Jeff was there as a guest of Kawasaki to help answer questions and just to bring his professionalism and friendliness to the intro. Plus, he always smells nice, so it’s good to have him around. Well, he and I started doing a moto on the new KXFs like we were racing for a national championship ... or at least a 30+ title at Loretta’s. Either way, it didn’t take long until I had forgotten that I was on an unfamiliar bike and I was riding flat-out. It wasn’t until that little grudge race was over that I realized how great the bike worked. We had pushed pretty hard for fifteen or twenty minutes and not once did I feel uncomfortable or out of control. I don’t think there’s a better testament to the way a bike works than that. The handling was predictable and stable. The brakes, shifting, and components were all excellent, and the Kawasaki has a very roomy, comfortable feel to it. And the motor, like I said, is unreal. Just like Max, I never bothered to adjust the clickers, and he weighs at least twenty pounds more than I do. I can only imagine how much better it would be if I had the patience to set the sag and adjust the clickers… maybe next time.

For now, the 2007 KX450F is poised to defend its title as the best machine in the big-bike class. Stay tuned for our Racer X Tested shootout.

The DLC coating looks so trick

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