Articles specific to Yamaha.
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In its eighth model year, the biggest of the Yamaha four-strokes is still making strides. Starting life as the Yamaha YZ400F before an incarnation as the YZ426F and its eventual landing at the displacement limit for four-strokes in the 250cc class, the YZ450F is the most decorated four-stroke in motocross racing. It was the first four-stroke to win a supercross in its prototype year at the 1997 Las Vegas Supercross, the production bike was the first four-stroke to win a National Motocross title the following year in 1998, and now it has become the first four-stroke to win the World Supercross Championship, in 2004 at the hands of Heath Voss. In 2005, the YZ450F receives numerous upgrades in order to further distance itself from the pack.
Not only is the YZ450F derived from the first-ever winning motocross four-stroke, but it is still the horsepower king on the racetrack, and many magazines agree. When it comes to brute power, the YZ450F is the bike to beat. And it didn’t go untouched for 2005 by any means. It was already the downright fastest bike in its class, and, in2005, that power is delivered in a much easier-to-manage fashion. The liquid-cooled, 450cc, four-stroke powerplant features a new cylinder-head design as well as a new piston design, and when combined with the newly designed clutch and air-boot, the power delivery has been smoothed out significantly. The smoother power delivery not only makes for lower lap-times, but it decreases the wear-and-tear on the rider as well, making it easier to go full-speed for a longer period of time.
The new YZ fork, upgraded for the second year in a row, is an Air/Oil Separate System design with TCV (transfer control valve) for stable damping, improved mid- to full-stroke performance and better rider feedback, and the rear shock receives numerous upgrades as well, including a redesigned swingarm for a 1.1-pound weight savings, increased rigidity and ride comfort, and a new shock to go along with it, which features a full-rebound oil-lock circuit for a smoother ride in the rough stuff and 12.4 inches of travel. All of this adds up to a more nimble, more flickable YZ. To complement the smoother power delivery, the YZ450F has a much smaller, lighter feel now as well.
To help haul it down from speed, the 2005 YZ450F features a newly designed front-brake system, which mates a rerouted, shorter front-brake hose with a 250mm front disc brake, providing an increased brake feeling and easier bleeding: It’s a simple concept - since the brake line itself is shorter, it contains less hydraulic fluid, and thus the feeling to the rider is more direct and brake bleeding is much quicker.
It leaves showroom floors with a high-quality aluminum handlebar this year from Renthal – long considered the gold standard. In the past, standard steel handlebars were frequently the first things replaced after purchase, but now that’s not necessary. Not only does that save more weight, but it also saves the buyer about $100 at the dealership. The 21-inch front and 19-inch rear high-end Excel rims provide outstanding durability and reduce un-sprung weight, which allows for optimal suspension performance and handling. Mounted to those high-end Excel rims are premium Dunlop 739 race tires. Plus, the YZ450F still features a trick works-style clutch lever with race-spec barrel adjuster for on-the-fly adjustments, as well as a handlebar-mounted hot-start lever for ease of starting after a fall or stall.
The YZ450F’s power has been tops for quite a long time, and add to that the new fork and the new, smoother power delivery, and what you have is an extremely fast, extremely capable, very serious four-stroke race machine. Suggested Retail: $6,399 USD.
Engine Type: 449cc, liquid-cooled, 5-valve, DOHC, four-stroke w/titanium valves
Bore x Stroke: 95.0 x 63.4mm
Compression Ratio: 12.3:1
Carburetion: 39mm Keihin FCR flat-slide w/throttle position sensor
Ignition: Digital CDI
Transmission: 4-speed w/multi-plate wet clutch
Final Drive: #520 chain
Suspension, Front: 48mm Kayaba inverted telescopic fork w/adj. comp. & rebound; 11.8" travel
Suspension, Rear: Kayaba shock w/adj. preload, comp. & rebound, separate hi/lo comp. adj.; 12.4" travel
Brakes, Front / Rear: 250mm floating disc / 245mm disc
Tires, Front / Rear: 80/100-21 Dunlop / 110/90-19 Dunlop
Dims: L 85.5"; W 32.6"; H 51.3", Wheelbase: 58.5", Seat Height: 39.2", Ground Clearance: 14.6"
Dry Weight: 220 lbs.
Fuel Capacity: 1.8 gallons
Color: Team Yamaha Blue/White
- Redesigned combustion chamber, piston, intake ports, carburetor jetting and airbox for improved combustion efficiency, resulting in smoother more controlled power delivery.
- Redesigned CDI unit for smoother more controlled power delivery.
- Primary drive gear ratio has been changed from 2.82 to 2.65:1, clutch spring rate is reduced 6 percent for lighter lever pull, and a new shift mechanism provides more positive shifting.
- All-new fork with TCV (transfer control valve) for stable damping, improved mid- to full-stroke performance and better rider feedback.
- New, aluminum Renthal handlebar is 90 grams lighter and more durable.
- Revised triple clamps for even better handling.
- Shorter, re-routed front brake hose for increased brake feel and easier bleeding.
- Stronger swingarm with stronger new linkage for better performance.
- Rear shock has a new, full-rebound oil lock circuit for a smoother ride.
- New-design rear sprocket and chain guide reduces wear, chain wobble, and noise for more efficient power transfer.
- Rear brake bracket is 35 grams lighter, and designed for easier rear wheel installation.
- New front fork protectors are larger for better coverage.
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