The Yamaha YZ450F is a four-stroke racing motocross bike built by Yamaha Motor Corporation . It was the successor to the previous YZ426F which was discontinued in 2003. It is credited by Cycle World and Dirt Rider magazines as the bike that started the four-stroke dirt bike revolution. The 2006 YZ250F and YZ450F were the first production motorcycles equipped with titanium suspension springs.
30-564: The WR450F is the enduro version of the YZ450F. For many years, the motocross world almost exclusively used two-stroke engines. AMA racing classes had three classes: 125 cc, 250 cc, and 500 cc with no provision for four strokes. Later on in 1993, The AMA rules had changed where the gigantic 500cc liquid-cooled engines were no longer able to race. Most riders considered four-stroke engine technology to be largely utilitarian and uncompetitive, relegated solely for trail riding. In 1996,
60-647: A motocross racer. Over the years the WR has benefited from the advances made in the YZ motocross version gaining displacement and advancements such as an aluminum frame and improved suspension. Over much of its life the weight of the WR450F has remained fairly constant ranging from 244 to 249 pounds dry weight . Yamaha introduced the WR 400F in 1998. The 400F is a 400 cc (24 cu in) four-stroke off-road motorcycle produced for three years, beginning in 1998 and ending in 2000 (only
90-540: A 12.5-1 compression ratio. In 1997, Yamaha rocked the motocross world with the introduction of the YZ400M prototype, a concept motorcycle which borrowed much technology from road racing. The YZM was far ahead of all competition among four-stroke motocross bikes. Doug Henry piloted the YZ400M to its first victory in 1997 at the Las Vegas Supercross. This was the first time any four-stroke had won an AMA event. The YZ400M
120-455: A motocross track. The 2005 YZ450F was the first YZ450F to feature KYB twin chamber cartridge forks . The YZ450F received a major update in 2006, with over 300 parts changed and improved. The power was smoothed out, and the bike was made easier to ride, putting to rest the complaint that the YZ had too much power. The transmission was returned to a more traditional five-speed. An all-new aluminum single backbone frame shaved another 10 pounds off
150-409: A revised chassis. KYB KYB Corporation ( KYB株式会社 , KYB kabushiki gaisha , formerly Kayaba Kogyo kabushiki gaisha ( カヤバ工業株式会社 ) until 1 October 2015) is a Japanese , Tokyo -based automotive company. Among KYB's main products company are shock absorbers , air suspensions , power steering systems , hydraulic pumps , motors, cylinders, and valves. It
180-449: Is lighter and stronger for reduced weight, greater rigidity and more compliant rear suspension action. While an anodized finish gives the bike a tricked out look. The 426 also includes a larger pivot shift for increased durability. A larger rear brake disc was also added which means greater stopping power. For 2003, the YZF received the biggest update in its history. First, the engine displacement
210-495: Is now a 4-valve head, the gas tank is located under the seat, the exhaust pipe exits the rear of the cylinder, and the air intake is now in the front of the bike. They have a new bi-lateral frame which allows for new improved steering and the new engine components. The entire package comes together to create a bike that is mass-centralized. The bike was introduced by Yamaha Factory Motocross rider James Stewart Jr. The top speed has been recorded at 80 mph stock. The 2014 YZ450F
240-677: Is one of the world's largest shock absorber manufacturers and it also has the largest market share of concrete mixer trucks in Japan, with 85% of the market. The company has 34 manufacturing plants and 62 offices in 21 countries. KYB's American aftermarket distribution of automotive shocks and struts is headquartered in Greenwood, Indiana , with additional KYB manufacturing and distribution facilities in metro Chicago , Southern California , and metro Indianapolis . KYB Americas employs more than 100 people in all facilities. Shocks and struts for vehicles are
270-450: The YZ400F motocross model. It is basically the racing YZ450F detuned slightly for more controllable power, with a headlight and lighting coil, softer suspension, a kickstand , lower noise specifications, larger radiators and lower emissions. The WR in the name indicates a wide-ratio gear box common to most enduro or trail bikes and stands in contrast to the close-ratio gearbox essential to
300-401: The 2002 YZ250 and YZ426F with a 58.7 inch wheelbase and 14.7 inches of ground clearance. This was the last WR to make use of a manual compression release for starting. For 2003, the engine displacement was increased to 449 cc (27.4 cu in), the fuel tank was reduced to 2.6 gallons and an electric starter was added as standard equipment. The 2005 WR weighed in at 244 pounds dry,
330-479: The AMA changed racing rules to allow 450 cc four strokes to compete in the same racing class as 250 cc two-strokes. Yamaha engineer Yoshiharu Nakayama first came up with the idea of creating the first competitive four-stroke race motocross bike. The Yamaha YZ400F was developed to fit into this category. It solved the power dilemma by borrowing superbike technology and giving the YZ a five-valve head, liquid cooling and
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#1732859314313360-527: The YZ was upgraded to 426 cc in 2000). The WR400F is related to the YZ400F, a motocross model. Like the YZ400, it was considered to be a groundbreaking model in motorcycle history, ushering in the four-stroke era which ended the dominance of two-stroke engines in motocross and offroad racing. While many modern performance four-stroke dirt bikes have been criticized for excessive rebuild costs and short motor lifespans,
390-404: The YZ400F's starting woes. The next year, in 2001, Yamaha replaced the previous steel valves with titanium ones. The new valves were more than forty percent lighter than the previous valves, allowing for lighter and softer valve springs, in turn allowing a quicker revving engine, improved throttle response, higher rev ceilings, and more power. The crankshaft was also reshaped and the whole assembly
420-431: The YZF, becoming the first rider to win a championship on a four-stroke motorcycle. This victory is considered by some to be the major turning point in the motocross world—for the first time, four strokes were considered a competitive racing machine. In 2000, Yamaha updated the YZ400F, increasing the displacement to 426 cc for greater power and throttle response. In addition, the carburetor and jets were updated to ease
450-604: The Yamaha WR400F has an impressive record of reliability, often attributed to its steel valves and generous oil capacity. In 2001 the WR400F's became the WR426F, increasing the displacement to 426 cc (26.0 cu in) for greater power and throttle response. A beefier YZ style clutch basket and plates than those on the WR400 improved clutch performance. Frame geometry was identical to
480-489: The aluminum frame, the 2007 WR450F saw a revised dry-sump engine, with a new balancer , cylinder head, and camshafts with less lift and duration than previous generations and restyled plastics. 2009 saw new graphics, and 2010 was not sold in the US. After 3 years of design, the all-new 2012 WR450F was released and featured a 2012 YZ250F frame, KYB SSS forks, fuel injection , and an altered motor position. Per Yamaha's designers,
510-553: The bike weighed 250 pounds. The bike had an 11,600 rpm redline power and torque close to its 250 cc two-stroke rivals. It benefited from engine compression braking, which allowed the engine to slow the bike down during deceleration, giving the brakes a rest. The 1998 YZ400F was the first bike to come stock with a Keihin FCR carburetor . In 1998, Doug Henry won the AMA National Motocross Championship aboard
540-540: The entire ergonomic package on this YZF is well thought out. The handlebars have a nice bend to them and are well-placed for good rider control and legroom. The footpegs are well-made units with a wide platform and sit in a position that keeps them from dragging in ruts without cramping a rider's legs." In 2002 Yamaha remapped the digital CD ignition system which delivers a more precise spark and optimal timing for faster, stronger response during hard acceleration, and less kickback during starting. Also an all-new swing-arm which
570-527: The most popular KYB products distributed in North America. Source The company between 1939 and 1941 developed several gliders , autogyros and research aircraft for the Imperial Japanese Army . These are: After the war, in 1954, the company built a gyrodyne , named Kayaba Heliplane . The development of this aircraft started in 1952 when Shiro Kayaba, the founder of the company, obtained
600-412: The motocross model such as stiffer suspension while maintaining electric start and the 18" rear wheel. For 2017, the WR450F largely remained the same, except for modifications to the air box cover as well as a change from silver to black rims. For 2018, the WR450F remained similar to the 2016-2017 models, with a large distinction being that the bike was no longer available to register as green sticker in
630-448: The oil filter. Carburetor tuning was modified to deal with starting and off-idle take off difficulties. Also in 2001 the subframe was changed from a steel to a blue painted aluminum style. In 2002 the blue painting was stopped and left to a bare aluminum look. Motorcycle.com says that "The gas tank is reasonably thin and allows good forward and backward movement while providing something nicely shaped to hold onto with your knees. In fact,
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#1732859314313660-586: The only modifications required to the YZ250F chassis were updated motor mounts. The engine was rotated back to move the center of gravity and improve handling For 2016, the WR was given the reverse slant, 4-valve, fuel injected motor previously available in the YZ450F since 2010. Yamaha also introduced a new model, the YZ450FX , a more Enduro competition oriented version of the off-road 450 utilizing more design elements of
690-477: The parallel pipe. A maximum of 15% of the power was transmitted to the front wheel at any time. Yamaha planned on building 250 2-Tracs in 2004, but only a few were built, which were used for enduro racing. 2006 was the last year of the steel frames. The 2003 and 2004 models were red sticker bikes in California. For 2007, the WR gained an aluminum frame dropping the weight from 249 to 246 pounds. In addition to
720-413: The seat height was reduced to 38 inches and the fuel tank was decreased to 2.1 gallons. The 2006 WR weighed in at 249 pounds dry and produced 42 horsepower. A limited production version of the WR450F was the WR450F 2-Trac, which featured 2-wheel drive . The gearbox output sprocket drove a short, fully enclosed chain to a pump, which in turn pushed the oil to the front hub via the pipe and back via
750-416: The state of California. 2018 also saw the removal of the kick starter. https://www.yamahamotorsports.com/off-road/models/2016/wr450f The 2019 WR450F saw a more powerful motor & updated frame. Other changes include a revised, more compact frame, new speed sensor, bigger fuel tank and one fastener airbox access. The 2021 WR450F saw new cylinder head, camshafts, piston and connecting rods as well as
780-402: The weight. The 2006 saw KYB SSS forks. 2007 saw camshaft and exhaust changes, moving power from low-RPMs to mid-RPMs. 2008-2009 furthered pushed the powerband towards the mid-RPMs. In September 8, 2009, Yamaha introduced its all-new YZ450F with fuel injection. The engine cylinder is rearward slanted, the crank rod angle has been changed to provide a more complete combustion, the 5-valve head
810-556: Was a new design the retained the backwards slant engine. The 2014 model has a wet-sump engine and an easy access air filter. The 2018 YZ450F features electric start and a Mikuni fuel injection system. The kickstarter was removed for this generation. Yamaha WR450F The Yamaha WR450F is an off-road motorcycle made by Yamaha Motor Company . It currently has a 450 cc (27 cu in) liquid-cooled single-cylinder engine. First offered in 1998 at 400cc, it shared many components and design concepts with
840-427: Was increased with 449 cc in compliance to the new AMA Motocross maximum displacement rule, the engine now produced over 52 hp (39 kW). Next, the frame and plastic were updated for a new, sleeker look. Additionally, the YZF's weight was decreased from its original 250 lb (110 kg) to 233 lb (106 kg). The bike made tremendous power; however, many thought that the bike had too much power for
870-475: Was redesigned for quicker throttle response and, Yamaha claimed, "less high-end horsepower loss." In addition to motor modifications, a few changes were made to the transmission to help contain the power and ensure longevity. The suspension also received a bit of an overhaul with the goal being reduced weight and smoother action throughout the stroke. Yamaha also designed a new exhaust pipe design so that exhaust header removal would no longer be required when replacing
900-417: Was the predecessor of the production YZ400F, which was released the next year. Yamaha introduced the YZ400F in production in 1998 after a successful AMA season in 1997. It was "the first modern production four-stroke motocrosser that was directly competitive against two-strokes." Initially, Yamaha targeted a dry weight of 233 pounds (106 kg) (on par with the 250 two-strokes of the time), but by production,
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