Yamaha YZ490: The Legendary Two-Stroke Motocross Icon

Yamaha YZ490 two-stroke motocross bike history and specifications

The Yamaha YZ490 is a legendary two-stroke motocross bike that has left an indelible mark on the history of off-road racing. Known for its raw power, aggressive design, and dominance on the track, the YZ490 was a force to be reckoned with during its production years. This article delves into the bike’s history, year-to-year changes, technical specifications, performance metrics, and enduring legacy.

History and Evolution of the Yamaha YZ490

The Yamaha YZ490 was introduced in the late 1970s as part of Yamaha’s YZ series, which was designed to compete in the fiercely competitive motocross arena. The YZ490 was Yamaha’s answer to the growing demand for high-displacement two-stroke bikes that could deliver unmatched power and performance. Over the years, the YZ490 underwent several updates and refinements, each aimed at improving its performance, handling, and reliability.

Year-to-Year Differences and Key Updates ****1978-1980: The Early Years**** 1978: The Yamaha YZ400 (predecessor to the YZ490) was introduced, featuring a 396cc air-cooled two-stroke engine. It set the stage for the YZ490 with its powerful engine and robust chassis.

1979: Yamaha increased the engine displacement to 465cc, creating the YZ465. This model featured improved suspension and a more aggressive powerband.

1980: The YZ465 received minor updates, including a revised exhaust system and improved carburetion. However, it was still not the YZ490.

1981-1982: The Birth of the YZ490

1981: The Yamaha YZ490 was officially launched, featuring a massive 490cc air-cooled two-stroke engine. This model was designed for expert riders, offering explosive power and torque.

1982: The YZ490 received updates to its suspension system, with longer travel forks and a redesigned rear monoshock. The chassis was also strengthened to handle the bike’s immense power.

1983-1985: Refinements and Improvements 1983: Yamaha introduced a new CDI ignition system, replacing the points ignition. This improved reliability and performance. The bike also received a new exhaust system and updated graphics.

1984: The YZ490 saw minor updates, including a revised carburetor and improved air filtration system. The suspension was further refined for better handling.

1985: This year marked the introduction of a water-cooled engine for the smaller YZ models, but the YZ490 remained air-cooled. The bike received updated plastics and a new seat design.

1986-1989: The Final Years 1986: The YZ490 received a major overhaul, with a new frame design and updated suspension components. The bike’s weight was reduced, and the power delivery was smoothed out for better control.

1987-1989: The YZ490 saw minimal changes during these years, as Yamaha shifted its focus to water-cooled models. Production of the YZ490 eventually ceased in the early 1990s.

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Technical Specifications of the Yamaha YZ490 Below is a detailed breakdown of the Yamaha YZ490’s specifications, based on the 1986 model (the most refined version of the bike):

Engine Type: Air-cooled, single-cylinder, two-stroke

Displacement: 488cc

Bore x Stroke: 87 mm x 82 mm

Compression Ratio: 8.6:1

Fuel System: Mikuni VM38SS carburetor

Ignition: CDI (Capacitor Discharge Ignition)

Starting System: Kick-start

Transmission: 5-speed constant mesh

Clutch: Wet multi-plate

Final Drive: Chain

Chassis and Suspension Frame Type: Steel semi-double cradle

Front Suspension: Telescopic fork, 11.8 inches (300 mm) of travel

Rear Suspension: Swingarm with monoshock, 12.2 inches (310 mm) of travel

Front Brake: Hydraulic disc, 10.6 inches (270 mm)

Rear Brake: Hydraulic disc, 9.4 inches (240 mm)

Front Tire: 80/100-21

Rear Tire: 110/90-19

Dimensions and Weight Wheelbase: 58.5 inches (1486 mm)

Ground Clearance: 13.4 inches (340 mm)

Seat Height: 38.2 inches (970 mm)

Fuel Capacity: 2.6 gallons (9.8 liters)

Weight: 245 lbs (111 kg)

Performance Metrics The Yamaha YZ490 was renowned for its explosive power and thrilling performance. Below are the estimated performance metrics for the 1986 model:

Horsepower: 55 hp @ 7,000 RPM

Torque: 55 Nm @ 6,500 RPM

Top Speed: 100 mph (160 kph)

0-60 mph: 4.5 seconds

Quarter Mile Time: 13 seconds

Braking Distance (60-0 mph): 30 meters

Fuel Efficiency: 25 mpg (10.6 kmpl)

Range: 120 miles (193 kilometers)

Racing Pedigree and Legacy The Yamaha YZ490 was a dominant force in motocross racing during its heyday. Its powerful engine and robust chassis made it a favorite among professional riders, who used it to clinch numerous victories and championships. The bike’s success on the track cemented its reputation as one of the most formidable motocross bikes of its era.

Even after production ceased, the YZ490 continued to inspire future generations of motocross bikes. Its legacy lives on in modern two-stroke and four-stroke machines, which owe much of their design and performance to the pioneering work done by Yamaha with the YZ490.

Pros and Cons of the Yamaha YZ490 Pros Powerhouse Performance: The YZ490’s 488cc engine delivered unmatched power and torque, making it a thrill to ride.

Precise Handling: The bike’s suspension and chassis were designed for optimal control and stability, even on rough terrains.

Durable Build: The YZ490 was built to withstand the rigors of motocross racing, with a robust frame and reliable components.

Iconic Design: The bike’s aggressive styling and Yamaha’s signature yellow-and-black color scheme made it an instant classic.

Racing Dominance: The YZ490’s success on the track solidified its place in motocross history.

Cons Intimidating Power: The bike’s raw power made it unsuitable for beginners or inexperienced riders.

Fuel Consumption: The high-performance engine was thirsty, resulting in lower fuel efficiency.

Maintenance Intensity: Regular maintenance was required to keep the bike running at its best.

Lack of Modern Features: Compared to newer models, the YZ490 lacked advanced features like water cooling and electric start.

Heavyweight: At 245 lbs, the bike was on the heavier side, which could affect maneuverability for some riders.

Conclusion: A Timeless Motocross Legend The Yamaha YZ490 remains a timeless icon in the world of motocross. Its raw power, aggressive design, and racing pedigree have earned it a place in the hearts of enthusiasts and collectors alike. While modern bikes have surpassed it in terms of technology and refinement, the YZ490’s legacy endures as a symbol of Yamaha’s commitment to innovation and performance.

Whether you’re a seasoned rider looking to relive the glory days of two-stroke motocross or a collector seeking a piece of motocross history, the Yamaha YZ490 is a bike that continues to inspire and captivate. Its roar on the track and its dominance in competition will forever be remembered as a golden chapter in the story of motocross.

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