The 2010 Yamaha YZ450F first ride impression from Dirt Rider Magazine is here. We just wrapped up our first day of testing the new YZ450F at the world-class Budds Creek MX facility in Maryland and it's safe to say that Yamaha has reinvented the YZ with the 2010's innovative engine configuration, fuel injection system and completely new frame/chassis.You already know what's new on the bike (if you need a reminder, click here for our 2010 Yamaha YZ450F Revealed story), but how does all that backwards-cylinder and under-seat fuel tank business work on the track? Let me tell you in one simple word: Awesome. The 2010 YZ450F is awesome. And maybe magic. Granted, this first impression is after ONE DAY of testing. But it was a pretty awesome day.Taking weight off a bike, as well as a rider's back, arms and legs and making it disappear into the motorcycle below is no easy feat. But Yamaha has done all of that by centralizing the mass of rotating forces inside their cylinder head and dropping the fuel under the seat (a completely new frame doesn't hurt, I'm sure). The bike feels just as heavy and bulky as other 450-class machines in the pits-pushing it around and hoisting it up and onto a stand will give zero insight into the ride. Even when seated, the bulbous radiator shrouds, doubling as direct air intake scoops to the under-tank air box, give an air of heft and undeniable girth. But looks are deceiving. When in motion, the bike feels svelte, slim, nimble and light. It's hard to describe but the 2009 Husaberg models are as close to a comparison as there is. This bike looses 40 percent of its mass when it starts rolling and feels like a really fast 250F.Have Yamaha's cornered as well as their competition in the past? No. At least not for everyone. Some could coax them to commit to the ruts but in general they were reluctant to follow your instincts into and through a corner. That feeling or inconsistency is gone. The 2010 YZ450F has a light-as-air steering feel. This fits in quite well with the weight feel of the bike being non-existent at your feet and butt. Corner initiation is almost automatic as the bike falls off it's upright axis and into whatever lean angle you choose. It doesn't flop over; it reacts predictably and when you decide it's gone far enough, it stops leaning. It followed the bends around Budds Creek beautifully. It was just as likeable in the air.We were blessed with a nicely prepped track with a few leftover bumps but most of the line-making was up to us, as the track went from flat prep to rutted choices, the Yamaha behaved great. It's nice riding a bike that gives you confidence in flat corners, tight ruts, off-cambers (and there are plenty at Budds!) and even the fastest straight we could find. Somehow, it seems, Yamaha has mixed minimal effort cornering with above par straight-line stability. I can't wait to get it out West to some familiar tracks to see how it compares. As of now, this chassis is a big, big winner. But really, we shouldn't take anything away from this motor.For 2010, someone replaced the YZ motor with a new animal. Dirt Rider Senior Editor Karel Kramer, who's ridden every year of Yamaha YZF before 99% of the world, commented that the 2010 motor is more different than the '09 than the 2010 chassis is different than the '09. And this chassis is different! Confused? I was too, but when we began discussing it he started to make sense (like normal)."When they reversed the cylinder head and tilted the motor back for 2010 it's like they flip-flopped the engine character or powerband as well," Kramer said. "Before, the bottom was soft and the bike would build smoothly into a great big top-end pull. Now, the bottom has serious punch with a heavy grunt and, while it seems to have plenty on top, it isn't yanking into orbit with an 'Oooooooman!' feel like the older bikes."You should have seen him do the "Oooooooman!" move in the desk chair of our hotel room. It was awesome. I think he covered the imaginary clutch and everything.Kramer's remarks are right on. The 2010 YZ450F has a new heartbeat. This motor must make more power than last year's and it surely delivers it with more ferocity. We have a ton of traction here at Budds Creek, so the bike isn't breaking loose, but it feels like it could if we found a gap in the grip. Here, we're getting nothing but serious acceleration and plenty of tug all the way through the mid. In fact, there might be a mid-range second wind that is almost as deliberate as the great bottom end 'snap'. I can see this bike going head-to-head with the Kawi down low. The motor is truly impressive and 180 degrees from where this bike was a year ago. It does retain most of its rideability but the new motor's punch and the directness of EFI demands respect. Stay on your toes or a seemingly harmless throttle blip could send you quickly into orbit.I wouldn't say this motor is as low-rpm friendly as the '09, and for sure it doesn't want to lug downstairs like that motor, but it makes more power for sure.So far, Yamaha's recent history of plush-yet-controlled suspension performance is rightfully intact. The front and rear suspenders are offering a controlled feel for all 175 pounds of my vet-class intermediate flogging. I even pretended to be a hero and went super fast for three corners and two straights and the bike didn't come close to buckling. It seems if you push the bike, it just tightens up more. If I picked up the pace somehow, I could use some tightening up of the movement through clickers or revalving to give optimum control for a truly higher skill level, but for local intermediates to pros, this seems to work fine (again after one day). And the beginners and novices out there will appreciate the plushness for sure.I have to complain about something. And it deserves a complaint. The YZ isn't easy to start. The piston absolutely has to be brought up to top dead center and your foot needs to push the kick-starter down smoothly (not in a hurry!). Then, she fires up pretty well. I also had a tendency to stall the YZF motor while doing photo loops and trying to push 2nd gear to ultra low-rpm. So I had plenty of practice kicking today. This bike feels so light when I ride it that I say, slap an electric starter and a battery on this baby! Maybe in the future. For now, I'll unhappily kick through a bit of procedure.Well, that's about it from day one here at Budds Creek and beautiful Maryland. We'll be out at the track again tomorrow for another day of testing. So, leave a comment below if you have any specific questions and I'll try to get back to them as soon as possible.