Yamaha says its all-new 2010 YZ450F is an revolution in contemporary motocross design. MotoUSA heads east to Budds Creek Motocross Park to put it to the test.
More than just an update, next year’s YZ450F is an all-new platform which incorporates numerous innovative engineering tricks that we’ve never seen on a mass-produced Japanese motocross bike. It’s the kind of advance that comes when a motorcycle is engineered as a whole with complete synergy between engine, chassis and, most importantly, rider.
Engine
Providing propulsion is a cleverly designed engine that is more powerful and increasingly more compact than ever before. Its 449cc displacement remains the same but inside it utilizes more oversquare 97 x 60.8mm internal piston dimensions. This wider bore, shorter stroke format allowed engineers to reduce cylinder height by over a half an inch. Additionally, the cylinder is tilted toward the front center of the crankshaft. This keeps the connecting rod more vertical during the compression stroke, thereby reducing friction between the piston and cylinder. This translates into more efficient combustion force. A matching piston with a narrower skirt area boosts the compression ratio to 12.5:1 and the piston pin is no longer offset in relation to its center. The piston rings have been reshaped and have less tension on them which reduces both friction and oil consumption.
Almost everything is brand-new on the new YZ450F. The only components unchanged are the wheels, brakes and tires.
Yamaha’s venerable five-valve cylinder head design has been replaced with a conventional four-valve setup, which is claimed to be more suitable for low-to-mid-range engine power characteristics. Two huge 36mm intake valves are now located at the front of the engine, while two 30mm exhaust valves are situated rearward. All the valves are still constructed from titanium. The valve springs are now oval in shape (as opposed to round). Both camshafts have been reshaped in order to deliver more lift from each of the valves.
Fresh air is routed to the engine from the front of the motorcycle. This design delivers a straighter air intake pathway with cleaner, less dusty air. A flat foam air filter sits inside the airbox and is accessed by removing a total of six bolts which hold both the seat and fuel tank.
A forward-mounted 44mm Keihin throttle body receives fuel from a 12-hole fuel-injector (pulled from Yamaha’s line of YZF sportbikes). The FI system is battery-less and powered by the engine’s AC generator. It uses seven sensors including intake air and atmospheric pressure, coolant and air temperature, throttle position, crankshaft position, and a G-meter, which feed information in real-time to the ECU in order to deliver perfect fuel mixture, regardless of where you ride. Additionally, the G-sensor shuts off fuel if it detects the motorcycle is on its side for longer than 10 seconds. Furthermore, the fuel and ignition maps can be modified via a self-powered and handheld $279.95 GYTR accessory Power Tuner (part no. 33D-H59C0-V0-00).
Exhaust is now pumped from the back of the engine and pushed through a stainless-steel header equipped with a resonator (allows for more exhaust volume) that curls back to a length of over four inches. Gasses are funneled into an aluminum muffler, nearly twice the size of the previous design, which is mounted on the right-hand side of the motorcycle.
Chassis
A new and very expensive looking twin-spar frame houses the engine nearly nine degrees behind its vertical axis. It’s comprised of 16 individual pieces of aluminum which allowed engineers to precisely tune each section of the frame for favorable feel around the racetrack. Swingarm rigidity was also tweaked. Between the top frame rails lies the 1.6-gallon plastic fuel tank which is translucent in color so it’s easier to view the fuel level during refueling. Both radiators have been lowered and tilted forward to assist in centering the bike’s mass without making the bike feel wider. Lastly, a plastic skid plate protects the underside of the engine from debris.
Suspension is a mix of old and new. The ultra plush Kayaba Speed Sensitive fork returns but gains additional stroke which brings suspension travel to 12.2 inches. The 0.47 kg/mm spring rate remains the same but the valving has been modified. Other changes inside the fork are a slicker parts treatment and a new oil seal shape. The fork is still adjustable for both compression and rebound damping.
The YZ’s extremely capable Kayaba suspension components have been tweaked for 2010. Overall performance is on a level no other production motocross bike can match.
What is new is the gas charged shock absorber, also made by Kayaba. It uses utilizes a larger 50mm piston and a reshaped, higher capacity nitrogen gas reservoir. The spring rate has been increased from 5.5 kg/mm to 5.7 kg/mm. Like before it still offers four-way adjustability for spring preload, high- and low-speed compression, and rebound damping. The shock is now positioned in the center of the bike, within the area that would typically be occupied by a conventional airbox. It provides 12.4 inches of movement and works though the same linkage as last year’s machine.
Other chassis modifications come in the form of a new top clamp with reduced offset to 22mm (from 25mm). This reduces the distance between the fork tubes and the steering head making the bike easier to steer. The clamp holds thick Pro Taper aluminum handlebars that have been repositioned lower and closer to the rider, but it still offers four positions of adjustment based on rider preference. Other ergonomic changes include the seat which is more level to help the rider ply their body fore or aft.
Visually, the YZ sports more sleek plastic body panels that accentuate both the engine and chassis and give it a futuristic look similar to its YZF-R series sportbikes. We think it looks awesome and really stands out from other manufactures' cookie-cutter 450 class offerings. Furthermore, a dark bronze surface treatment was applied to the engine’s side covers, fork legs and tube clamping surface designed to better resist scratching and normal wear and tear.
The engines’ bottom-end power is just one area of substantial improvement over last year’s machine.
How it Works
Lifting this new generation 450 off its stand reveals that it’s still no featherweight. Yamaha claims that the bike has gained five pounds over last year’s, bringing it to 245 lbs with a full load of fuel. Hop aboard, and you’ll be pleased that its width is exactly the same as last year. This is a big plus, considering the trend for this style of motorcycle becoming increasingly narrow. The cockpit is spacious for a six-foot-tall rider, though we do wish the handlebar was mounted higher. Fortunately Yamaha provides a $98.95 accessory GYTR Tall Bar Mounts option (part no. 33D-F34D0-V0-00) that raises the handlebar by 5mm.
The engine starting procedure is now as simple as jumping on the kickstart lever as both the fuel on/off switch and handlebar mounted hot start lever have been eliminated. If you’re lucky (or if the piston is at top-dead-center) the engine will fire right to life. If it isn’t at that sweet spot it’ll take an extra kick or two to get it fired. A cold start aka fast idle knob is located on the throttle body for use in cooler conditions.
The venue of choice for our ride introduction was Budds Creek Motocross Park in southern Maryland. The same east coast racetrack that the pros bar bang around in the AMA Motocross series and the site of the 2007 Motocross of Nations. In terms of track preparation, the folks from Budds went all-out, completely leveling the track each morning. Some overnight rain on the second day kept the track tacky and moist.
Out on track the first thing one observes is just how peppy the new engine is. Budds has numerous steep climbs that really load the engine and expose any shortcoming. We came away really impressed by not only how powerful the engine is but how easy that power is to use. Power comes on now, now, and NOW! Granted, lack of traction certainly wasn’t a variable at Budds Creek, thus as soon as you crack open the throttle, the YZ‘s 120-series Dunlop tire digs into the earth driving you forward hard.
Despite weighing 5 lbs. more than last year, the new YZ450F feels lighter and more maneuverable in the air.
Bottom-end is stout and transitions seamlessly into an even more impressive mid-range. Yet the engine produces power in a ridiculously linear fashion that doesn’t catch you off guard or feel like its going pull your arms off. It’s very robust feeling and feels on par with the current 450 class reigning power king, the Kawasaki KX450F. Again, the fact that the bike isn’t too narrow provides the rider enough surface area to comfortably squeeze the bike thereby locking you in place during wide-open acceleration.
In terms of overall excitement and sheer thrill factor, Yamaha continues to up the ante with the new YZ450F. Its engine features a unique character and during acceleration the roar from the front intake is unlike anything else on the dirt. It overwhelms the exhaust note and makes you feel like you’re moving way faster than you probably are.
The Yamaha’s 5-speed transmission, clutch, and versatile final drive gearing complement the engine perfectly. The transmission is both precise and tight feeling without a hint of slop. At times, however, it was difficult to upshift during full throttle acceleration. Neutral was also a bit tricky to find. Perhaps some more break-in time will remedy both issues. Clutch lever pull is wispy and overall feel is excellent. Gearing was equally remarkable and we never felt like we were between gears on any section of the track.
When barreling downhill, the Kayaba suspension pieces are the definition of plush. Not only do they soak up the rough stuff, it keeps the chassis completely in-line during aggressive deceleration. Also of note is just how balanced the suspension is front-to-rear. Furthermore, both the fork and shock offer precise damping adjustment. We also love the bike’s extra-wide footpegs which aid your body in soaking up jump landings. Equally effective are both the front and rear brakes which are more than capable of dissipating downhill momentum despite being one of the few components that remain unchanged for 2010.
The YZ retains its friendly ergonomics packing including its thick Pro Taper handlebars and humungous footpegs.
Besides engine performance, the most notable feature of the new Yamaha is the way it steers. Simply put, this is the best handling production 450 motocross bike we've experienced. Seriously. The YZ turns like no other motocross bike I’ve ever ridden. In fact, it handles so differently, it takes your brain some time to acclimate to its unique steering manners. Initiating a turn is almost effortless, yet at the same time the front end is extremely precise - never turning more or less than what the rider asks. The bike carries its weight low and doesn’t exhibit a hint of top-heaviness that is typical with other big-bore off-road bikes.
Dip into a turn and the front tire offers a ridiculous amount of bite. It’s as if there is 80 pounds of lead ballast directly behind the front wheel. Pick a line, steer the bike and it rolls right in as if you were playing a video game. Once turning, the chassis settles immediately. Fan the clutch lever and tug on the throttle and the bike zips right out of the turn while maintaining its trajectory, resisting the urge to stand up too much or run wide. Recommend rider sag is between 100 and 105mm. We set it at 104mm and had zero complaints in terms of how quick it steered or its outright stability through faster, third-gear sections of the track. It’s simply astounding how nimble it is without compromising stability.
Believe the hype. The 2010 Yamaha YZ450F performs as well as it looks. Pictured above is the optional Red/White color scheme that comes with black wheels and a gold chain. It costs $8090 and will be in dealerships in mid-November.
Every year, new bikes come and go. But after riding this latest YZ-F, it proved to be something special. It’s a radical departure from the status quo within the off-road motorcycle realm and it just plain works. Not only is its engine powerful, it’s friendly and easy-to-use. Handling is as accurate as a sniper's bullet, plus its ergonomics package allows one to fully take advantage of the bike’s phenomenal performance. But the most astounding feature is price. Even with its use of expensive, cutting-edge technology, the price tag comes in under eight grand. Not to mention Yamaha is the only manufacturer to stand behind its product with a 30-day warranty. Of all the new bikes I’ve ridden recently—both on the street and the dirt—this YZ is without a doubt my new favorite. Thank you Yamaha for building the perfect 450 MX’er.
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