2008 Yamaha YZ450F First Ride

Adam Waheed | November 19, 2007
2008 Yamaha YZ450F Intro Lead Graphic
We traveled to the Milestone Motocross Park to do our best impersonation of AMA Motocross Champion Grant Langston aboard the 2008 Yamaha YZ450F.

“Our most powerful, most flickable 450 ever,” I’ve heard that statement every single year since my first and last experience on Yamaha’s YZ450F. Riding that beast of a machine around I-5 MX Park was probably the worse motocross experience I’ve ever had in my, albeit short, motocross history. The only thing I really recall (concussions have a way of making things hard to remember) is thinking that 450s are way too powerful and they are seemingly willing to kill you at anytime.

Given this less than fond memory that has been forever etched in my cranium, when our Off-road Editor told me to assemble my gear and meet him out at Milestone Motocross Park for a day of testing Yamaha’s 2008 YZ450F, I was a bit apprehensive. Actually, I was scared. I didn’t want to have anything to do with the big-bore machine. The stage was set for another brain cell-killing experience.

Yamaha’s 450 first jumped on the motocross scene in 2003 following the YZ400F and YZ426F incarnations. Since then, Yamaha has chosen to constantly tweak and refine the big-bore thumper rather than do a complete model revamp. Yamaha’s updated YZ-F had already established itself even before we got a chance to have a go on the bike. Just ask Factory Yamaha’s Grant Langston. He piloted his ’08 four-fifty to the top in this year’s AMA Motocross Championship. Then he went on to steal the show with the overall win at the Rockstar U.S. Open in Las Vegas, Nevada-proving that the bike is capable indoors and out.

Between those stylin’ new matte black crankcase covers is a liquid-cooled 449cc DOHC 4-stroke engine. The motor retains Yamaha’s symbolic 5-titanium valve head, but features revised intake port shapes and updated intake and exhaust cam profiles that help with combustion efficiency and also simultaneously improve torque and throttle response.

Catching air on the big thumper is no problem thanks to the YZ s modified 449cc DOHC 4-stroker.
Catching air on the big thumper is no problem thanks to the YZ’s modified 449cc DOHC 4-stroker while landing is smoothed out thanks to Kabayas up front and back.

Displacement is courtesy of the 95mm x 63.4mm bore/stroke that gets squeezed to a 12.3:1 compression ratio. Piston and cylinder tolerances have been further reduced which helps cut down on unwanted mechanical racket, and we can’t report any excessive shake, rattle or roll from the engine. A throttle position sensor-equipped 39mm Keihin FCR flat-side carburetor copiously feeds the fast-revving engine, and spent fuel gets passed via the new, larger-diameter titanium exhaust header that’s connected to a shorty-style “punched cone” muffler.

You wouldn’t think that those little engine modifications would add up to much but on the bike they make all the difference in the world.

My senses were immediately assaulted as soon as I swung a leg over the YZ-F. The bike feels exceptionally slim between your legs, not quite as slim as a 250F, but the layouts are getting very close these days. The high-quality ProTaper aluminum handlebars have a comfortable bend and can accommodate both short and tall riders, though one of our testers feel they are a bit too swept for his comfort. Cracking the throttle exposed the smooth yet aggressive powerband. To say that the new 450 motor is much smoother than years previous would be an understatement. The engine has an incredibly linear power band from just off idle that rapidly crescendos all the way to its strong top-end. If you’re looking for any kind of big power hit or surge, you won’t find it on this bike. Last year, some of our shootout testers thought the bottom end could have used a little extra jolt, but in the end it was the smoothness that helped them turn fast laps. We were happy to find that the 2008 model has some extra juice down low.

“The biggest thing Yamaha has done to this motor is smoothen out its power delivery. It actually feels a bit slower (than previous models) but I think it’s because the powerband is so much more linear now,” comments our ringer Alvin Zalamea. “The bike’s got a great bottom-end and it makes really consistent power throughout the rev range. It will be interesting to see the power curve on a dyno.”

Changes to the YZ450F s chassis left a positive impression on our testers and made them fearless through the ruts.
Changes to the YZ450F’s chassis and a shorter steering head pipe and stem left positive impressions on our testers and made them fearless through the ruts.

The five-speed close-ratio gearbox returns this year and is mated to the cable-actuated clutch which has a super easy lever pull. All of our riders felt that the gearing was a tad off for the sandy Milestone circuit, but were confident an additional tooth or two on the rear sprocket would have solved the problem.

“Second gear felt a little short, and third gear was a bit too tall, but the super light pull at the clutch lever made it easy to carry third gear coming into a corner and then just slip the clutch a bit to get the Rs up. Clutch pull isn’t as light as a 250F yet but it’s definitely much improved,” comments Mr. Z.

Externally the big-bore Yamaha sports a revised aluminum frame that features tuned-flex design technologies allowing for the use of different alloy castings. Additionally, the steering head pipe and steering stem are 5mm shorter and the forged lower triple clamp is lighter which helps the 450 turn much more quickly than in years past, which all of our testers noted. New, wider 55mm footpegs complete the list of changes to the blue thumper.

“Man, I love those wider footpegs! They look like they’re one-off works components, and they actually perform,” says AZ. “I really felt the difference when boogying through the whoops and any rhythm section. It made it easier on my feet with the wider surface area, and I just felt a lot more stable on the machine.”
Attached to the trick-looking aluminum frame up front is a new speed-sensitive 48mm Kayaba fork that features all the usual compression and rebound damping adjustments. There are 11.6-inches of travel before hitting the bump-stop and the new fork features transfer control valves above the fork springs that allow damping force to be controlled by piston speed, which ensures more consistent damping. A new lighter axle and collar also help to further remove weight from the YZ-F’s front end.

The rear on the 2008 Yamaha YZ450F has a wider 120 80-19 Dunlop D756 and a 245mm single wave-style disc brake.
The back end on YZ450F got a little wider for 2008 and measures out at 120/80-19. Putting a halt to the action is a 245mm single wave-style disc brake.

Out back, the Kayaba rear shock now compresses a new lightweight titanium shock spring that decreases unsprung weight as well as improving shock action. The shock features 12.4-inches of travel and has all the standard adjustments: high/low speed compression damping, rebound damping and spring preload. An optimized linkage connects the rear shock to the tapered aluminum swingarm and provides a smoother ride as well as improved rear wheel traction.

The changes made to the chassis are 100% noticeable on the track. The chassis is razor sharp with the new front end willing to hunt down ruts. And when the front wheel finds what it’s looking for, it sticks like gum on the bottom of your shoe.

“The bike turns much, much better than before. The front end just sticks now where before it would seem like it would plow a bit,” says Zalamea.

Suspension action is improved as well. Whether it be blasting through tall, peaky whoops or overshooting a jump (which I seem to be best at), the new suspension has got what it takes to keep you from looking like an idiot.

“Suspension action is much improved over last year’s bike. The bike tracks dead straight through whoops and both the fork and the shock seem to soak up hits in a much more smooth and controlled fashion,” Alvin Z admits.

The new 80/100-21 front Dunlop D742FA tire is now stopped via a YZ250F-style front brake caliper that clamps down on a lighter wave-style 250mm rotor. The new front brake is incredibly powerful and offers tons of feel which give the rider the confidence to mash the binders before coming into a tight turn. Out back a wider 120/80-19 Dunlop D756 tire puts the power down and is kept in check by the 245mm single wave-style disc brake.

Let  er rip  AZ. Once again  Zalamea beckoned MCUSA s call when it came time to put the YZ fo-fifty to the test.
A refined mill and an updated chassis mean the YZ450F is badder than ever. Now we’re chompin’ at the bit to match it head to head against the other 2008 four-fifties to see who will rule the dirt.

“The stock tires on this bike are really good – especially the rear. I don’t know if it’s more the bigger tire or the revised suspension linkage, but the rear hooks up more than Mindfreak’s Criss Angel in a Vegas night club,” commented Zalamea. “(The) brakes are really good too. Same amount of power as last year’s but the level of feel at both levers is improved.”

After a full-day aboard the new YZ450F my experience couldn’t have been more different from my first one. Instead of coming back battered and bruised, I was fully intact and hungry for more.

It’s pretty clear why Langston has had so much success on the new YZ-F. Bottom line is that the bike just plain rips! The Yamaha mill always had a ton of power, but now the bike makes power in a much more refined, tractable way – which makes riding the blue machine way easier. The refined engine is matched to an even more fabulous chassis which handles head and shoulders above the 2007 model.

“If this new Yamaha is any indication of things to come in the motocross world, than life is becoming better and better. Riding this bike makes me count the days until we can put it head-to-head with the rest of the 450s,” Alvin explained.

And if you feel like you just don’t have enough choices in life -Yamaha has your back cause’ this trickle-down motocross race technology can be had in two distinguished colors: The race-replica blue/white color scheme will set you back $7,099 and you’ll pay an extra hundred dollars for the white/red version. You may not be quite as fast as Motocross champ, Grant Langston – but at least you can look like him and benefit from Yamaha’s years of motocross racing experience.

Let us know what you think about the 2008 Yamaha YZ450F in the MCUSA Forum. Click Here

Adam Waheed

Road Test Editor | Articles | Adam’s insatiable thirst for life is only surpassed by his monthly fuel bill. Whether rocketing on land, flying through the air, or jumping the seas, our Road Test Editor does it all and has the scars to prove it.