Kirk Overby: 6'- 2" Weight: Heavy Age: Old enough Experience:Vet Intermediate Rider (Super Squid in MX)

WOW! What an engine! The engine pulls like a Saturn 5 rocket, on steroids! You can really feel the bike tug on the handlebars when you tweak the throttle. The engine has great low-end and its power moves very quickly into the mid and upper RPM's. The light flywheel lets the engine rip to the moon. Yamaha states the engine can rev to 11,000 RPM, and it does, with big power on tap. On Carlsbad's long uphill, I cranked on the throttle hard and shifted like a banshee all the way up the hill. The bike literally catapulted its way up the hill!

The braking power was typical Yamaha. Just plain good. The transmission shifting was fine. Yea, it could be smoother - but, it's a Yamaha.

How does it handle? As long as I had the throttle cranked, and rode aggressively, the YZ literally flowed around the track, usually. It was really hard for me to get used to railing berms, and riding through corners.

Overall, this is an insanely powerful bike with many good handling characteristics. It simply doesn't inspire confidence when I'm cornering.

And to answer everyone's burning question, no, I wouldn't like to own one. I can get around an MX track easier with the YZ 250.

Mike Hobbs: 6'- 1" Weight: Not as heavy as Kirk Age: Young Experience:Good Vet Rider!

There's been a lot of whining and crying about starting "Blue Thunder." Is it hard to start? Nope, not if you have owned a manual compression release 4-stroke in the past. Now, if you're a 2-stroke convert, it may take you a few minutes to get the starting drill down.

Here's the good, the bad, and knurly while riding Carlsbad Motocross track in wet and sloppy mud. The motor flat out rips apart any 4-stroke on the market, it's that good! It revs out of the Solar System, and back, with dominating force. My '97 YZ 250 power almost seemed dull in comparison. I rode a few timid laps and the YZF manhandled me. Blue Thunder is an MX bike that demands aggressive riding, period. When riding aggressively, the power is manageable and in abundance. Wicking the throttle will bring the front wheel up, even in deep mud. (Try that on a 2-stroke and see what happens.) The harder I rode the better the bike felt. In fact, it wanted to be ridden harder than I could ride it.

This bike jumps well and even seems flickable in the air. The only reason I didn't try a Nac-Nac is because I can't do one. The handling is good and very close to the YZ 250. Although, the front suspension didn't quite work for me, I'm sure a few minor click adjustments would fix this.

The lack of flywheel weight is apparent, the bike stalls easily and there is no compression braking. The riding position is aggressive and comfortable. After trying my hardiest to find a flaw in the YZF, it happened. Diving into a berm with the throttle closed, I wicked it wide open. A small burp bellowed from the YZF, loosing power for a second. This was just enough to put me on my butt with Kirk snapping pictures and laughing his derriere off!

Yamaha did a magnificent job building the YZF but, if you want an Off-Road bike wait for the WRF to be released. On the other hand if you want one BAD SOB MX bike, it's here in the YZ400F! I only wish we could have ridden it a bit longer. Is it the "Bike of the year?" There is no doubt in my mind that it is!

Rick Sieman: 5'- Uh...?" Weight: Adjustable Age: "Don't Ask" Experience:Vet Expert Rider

As with the over-whelming majority of the press, I was prepared to be mightily over-whelmed by Yamaha's all new deadly serious four-stroke. And why not? It looked great, sounded like a real thumper, didn't carry a bunch of excess weight, and showed it could run with the two-strokes under any condition from desert to supercross. At least in the hands of expert-level riders.

I picked one of the many bikes that Yamaha had prepped for our test session at Carlsbad Raceway,

From the starting gate to the first turn, the acceleration was so fierce that it bordered on intimidating! Power started early in the revs, pulled hard at mid-range and then screamed out on top like a road racer!

This was so much fun that I went back to the starting line and did this another half-dozen times. Once I got used to the way the YZ-400F hit, I found that I could actually torque the blue beast up into a wheelie easily in the bottom three gears.

Now, this might not sound like such a big deal to you young punks out there who can wheelie a golf cart with ease,

But here I was now, simply rolling the throttle on and watching the front end loft gently up, and able to hold it there by adding more throttle. Is it too late to change careers and become the next Wheelie King?

After a few easy laps around the course, I was convinced that the YZ-400F was the best thing to happen since 21-year old strippers who want to be my intern.

However, as with most bikes, the true personality doesn't emerge until you push the machine to its limits, or your own personal limits. Here's what I found out about this new bike after putting in many laps:

Though it weighs about 20 pounds more than a typical two stroke, the extra weight is not felt under most riding conditions.

Shifting is typical Yamaha, which means that you won't miss any gears, but it's on the notchy side compared to other brands. A Honda XR-400 shifts smoother than the YZ-400. After a while, you forget about the shifting, and will you shift much less with the YZ-400 than with a conventional two-stroke. No real complaints about the shifting, or gear ratios.

Suspension was good, but on the firm side. There was a "slap down" feel in the forks when landing from a jump. To be fair about this, all of the settings were as delivered stock, and rain shortened our test day to prevent playing with the clickers and pre-load settings.

Layout and feel of the bike (please note that I didn't use that horribly overworked word "ergonomics" here) is natural and nothing gets in the way. Stabbing at the brake pedal and nudging the shifter requires no thinking, which is good.

Bars and controls are first rate, and the bike even comes with truly wonderful grips. The kick starter is placed high and is slightly awkward to use if you're short. Since I have a 14 inch inseam, constant use of a milk crate was required. If I was going to enter a desert race with this bike,I would probably have to carry a milk crate in my fanny pack.

A bit more about the power: the 400F will rev out past 11,000 rpm without falling on its face, but there is a slight hitch n the power delivery right around 4200 or so. The hitch doesn't happen all the time, just when you whack the throttle open in too tall of a gear at low revs. If you roll the throttle on, the hitch stays in the barn.

There is something about the power that is bizarre, especially if you have lots of time riding four-strokes. On a typical four stroke, when you chop the throttle the engine braking is dramatic; very little rear brake is needed, and some high-compressioned four-strokes actually chatter the rear wheel when the throttle is chopped.

With the 400F, this trait is not present to the degree most riders are used to. Certainly, there is some engine compression braking, but not what you expect. This affects the handling big time! How? Read on.

Since the 400 is simply a new generation four-stroke motor cleverly stuffed into a YZ-250 chassis, you might think it would handle like the YZ-250. Not even close!

This bike does not handle like a YZ-250 and it does not handle like a typical four stroke. And here's where the confusion is: the YZ-400F demands that the rider learn a completely new riding style for motocross.

Let's explain it this way: When you dive into a corner with a four-stroke, you back off the throttle and instantly, engine compression makes the weight transfer forward, planting the front wheel. Combined with proper use of the front brake, that front wheel is literally buried in the corner.

When you decide it's time to complete the turn, you release the front brake and hit the throttle. The bike will make its pivot and you drive hard out of the corner.

Now, let's examine how the YZ-400F reacts in a turn: You approach the corner in the normal fashion, chop the throttle and the chassis does not transfer any appreciable amount of weight. You're forced to use almost as much rear brake as you would with a two-stroke.

The front wheel does not "plant" itself in the turn. If you're pushing against a nice berm, you're forced to rail-it a bit. The 400F doesn't lend itself to super tight pivot turns you can do on a typical quick-handling two-stroke.