The 2010 Kawasaki KX450F was given to Dirt Rider and super test rider dude Ryan Orr yesterday at the new Pala Raceway in Southern California. We spent a solid day testing and tuning the big new KX450F and we learned a lot about some of the big changes Kawasaki made for 2010.Looks are deceiving. And if you think this looks like the bike Ryan Villopoto graced our cover on months ago, you’re right. It has the same numbers on it! We missed our shipment of cool new digits but thought Villopoto’s big #2 was more than adequate for this first impression. Even without the factory number, the 2010 KX450F looks almost exactly like the 2009 save for seat coloring, some slight graphics and color swaps and subtle visible hardware updates like the new exhaust system.We won’t get into everything new on the KX450F here. This is our riding impression, after all. If you want a quick hit of what’s new, click over to what’s new on the 2010 KX450F. Plus, I’ll be updating a new story on everything new we learned today about what Kawasaki changed. For now, let’s get to the riding impression.The 2010 Kawasaki KX450F is probably the fastest 450 in the class. I’m saying that completely blind since it’s the only 2010 450 Motocross bike I’ve ridden but after one twist of the throttle on this green monster it’s not that strange of an assumption.Throttle response is insane. It’s sharp and with its bark comes a healthy punch of power directed to whatever poor dirt inhabitant is under or directly behind the rear tire. It’s no wonder the clutch friction plates were updated for 2010. If they’re stronger as advertised, they’ll come in handy. Both myself and pro-level test rider Ryan Orr used the clutch often to keep the front end down and we needed it. The clutch on the KX450 seems to be a great power regulator.The 2010 KX450F’s power character from initial response to the very, very top end can best be described as all encompassing. That is, it doesn’t really care what sort of riding style you throw at it. You can lug it in the ruts or rev it outside. It’s equally potent in the upper rpm off jump faces as it is under full short-shift mode and simply cruising. The only time the power doesn’t cooperate is when you’re not ready for it. This bike should come with a little speaker on the handlebar that squawks, “You’re riding a KX450, dummy. Get ready.” That way, you know what’s coming and can get ready for it. Then, you won’t be as surprised and less likely to suffer from surprise arm-pumpage.Even with its voracity, the big Kawasaki does show some manners. Other than slipping the clutch, the precise throttle control of the bike does wonders for keeping things in line. These new EFI bikes are electric-if you want a brighter spark, roll on the switch. Also, the bike doesn’t feel nearly as last year’s bike under acceleration and during slow-down. The new KX450F is hiding some of the bulky reciprocating mass inside the motor for sure. There are some Crankshaft mass changes as well as cylinder and piston updates contributing to this. In general, the motor is simply great on this bike. Pala Raceway is pretty good for a one-day test. It combines a wide-open back half with an inter-mixed blend of jumps and turns. There’s a wide-open step-up and some quick, out-of-corner doubles all waiting for you. The mere bulk of Kawasaki power made short work of all track obstacles.Did you know the target weight of a KX450F rider is 185 pounds? I found that out today while Orr and I dialed in suspension settings with KYB technicians. Because of the rather hefty target weight (compared to the scrawny moto kids I see ripping around on these things), Kawasaki pumped up the spring rates front and rear on the 2010 KX450F. To control the stiffer springs, there is more rebound damping and less compression. The ride is a mixed combination of plush with just a touch of harshness in the fork. The bike is extremely picky about sag settings (as it was in 2009) and the difference between 102mm and 100mm will surprise you. We ran it at 100mm with the best luck. There, the shock seems happy and we left it mostly alone with its stock settings clicked in. We messed with the fork quite a bit, though. Basically, we were felling some harshness in the fork and opened up the rebound and softened the compression to battle it. We’re talking increments of 1-2 clicks here so we’re far from a final setting. Plus, we didn’t have a lot of bumps to play with-but we’re going to find some this week.In general, the bike’s front end has a “heavy spring” sort of feel to it but the open compression damping is making it usable for guys like me (175-or so pounds) and Ryan Orr (165-or so pounds). We want it to settle more and have a more confidence-inspiring balance from straights to corners, but we look to get there with more testing in the following weeks. This is all with an increase in the light “feel” of the front end. Not just while steering, but during the entire ride. The chassis rigidity tuning (a less rigid steering tube and tweaks to get more flex into the swingarm) seems to have lightened up the front end and put more flex into the chassis all around. So far, this is a good thing.A few other updates on the 2010 Kawasaki KX450F are immediately noticeable as well. The stock exhaust is decent, finally. It still doesn’t sound super clean but at least it isn’t ear shocking like last year’s bike was. The new rubber-mounted muffler seems to be working decently. The header pipe is 40mm shorter and makes a straight shot back-no more drop out of the cylinder. And the radiators are beefed up in size and in spacing between the fins. The seat has some firmness added that was much needed and a nice colored dual-gripper cover.Ryan Orr sent me his first impression via Blackberry (since he’s technically on vacation). Here are his thoughts on the new Kawasaki:My first impression of the twenty ten KX 450 is that it’s basically a rocket strapped to a rolling chassis. The motor has that same great EFI response, strong mid, and great pull up top as the 09 model. The bike pulls in any gear whether you’re over revving it or lugging the crap out of it. The handling was almost on par with last year’s bike. It just took some fine-tuning to get the bike settled in. The spring rates are a little firmer for 2010 and I think the 09 spring rates worked best for my weight and riding style. The bike has that same great straight stability as well as a steering-the-bike-with-the-rear-end characteristic as last year. Coming out of corners I could pick a point and go as well as change my line easily of there was an unexpected obstacle. The bike also feels light and easy to flick around in the air. The new KX 450 is a great all around MXer. Can’t wait to test it back-to-back with the rest of the other 450s!–Ryan OrrAs the first 450 out of the gates in 2010, Kawasaki seems to be pulling a big holeshot with gobs of power and a set up favoring the bigger/faster pilots out there.Look for updates here on www.dirtrider.com including a complete first test in the pages of Dirt Rider Magazine. Discuss the newest ride from Kawasaki in our Forums while you wait!