Specifications of the 490 Engine in the 1984 Yamaha IT
The Yamaha IT 490 motorcycle was only produced in 1983 and 1984. The bike was identical in both years. It featured a single-cylinder, two-stroke engine. The IT 490 was an Enduro-class motorcycle. It was similar to other bikes in that class except that the Yamaha IT 490 was designed for use in competitions and thus was more powerful.
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Horsepower
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Horsepower is a measurement of the amount of work an engine is capable of doing over time. It is a traditional measurement used to indicate the power of cars and motorcycles. One unit of horsepower equals 745.699872 watts. Engine horsepower is expressed as a value that indicates the maximum power of the vehicle. Since an engine will produce different amounts of power depending upon how fast the motorcycle is going, the maximum horsepower is stated in terms of revolutions per minute. The 1984 Yamaha IT 490 had a maximum horsepower of 35 hp at 6,000 rpm.
Torque
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Torque, another traditional measurement used to indicated the power of an engine, is a measurement of rotational force. Torque represents the amount of force that drives the wheels forward. Since it measures rotational force, torque is also indicated as a maximum value in terms of revolutions per minute. The actual torque that a bike produces will change depending on how it is driven. The maximum torque for the 1984 Yamaha IT 490 was 31 foot-pounds at 5,500 rpm.
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Displacement
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The 1984 Yamaha IT gets the "490" in its name from the engine's displacement. Displacement is also another traditional measurement of an engine's power. Since internal combustion engines work by sweeping air into the cylinders and using that to drive the vehicle, the total volume of air swept, or displaced, by the engine gives an indication of the vehicle's power. The name of the Yamaha IT 490 is something of a misnomer. The displacement was rounded up. The actual displacement was 487 cubic centimeters, which is the equivalent of 29.72 cubic inches.
Compression
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Engine compression is a ratio that indicates the difference between volume of the combustion chamber at its largest capacity and its smallest capacity. As the pistons move up and down, a different volume of air can be contained in the chamber. Compression represents that difference. The 1984 Yamaha IT 490 had a compression ratio of 4.9 to 1.
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