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Senin, 24 Maret 2008

1981 CR250R

Turn back the clock some 21 years, and take a look around the landscape of American motocross. With the exception of a few special factory-built racing bikes, all production 250 motocross machines are air-cooled.

That changed in 1981 when Honda introduced the CR250R, motorcycling's first production liquid-cooled 250 motocross racer. Now utterly commonplace in every facet of motorcycling, 20 years ago liquid-cooling was cutting-edge, state-of-the-art. The CR250R took advantage of liquid-cooling's inherent benefits; not only does liquid cooling allow an engine to run cooler, it also keeps it in a more consistent temperature range. That means higher and more consistent power output. Honda's own research showed that in the first 20 minutes of a race, an air-cooled engine would lose nearly 30 percent — almost one-third — of its peak horsepower. That's why Honda provided its team riders with exotic liquid-cooled 250s in 1980.

The 1981 CR250R brought that exotic technology to the production line, and the bike appeared amazingly similar to its one-off, exotic factory-built cousin. The engines shared the same bore-and-stroke dimensions (both were long-stroke designs, yielding a taller cylinder that allowed more room for optimal port shapes), center exhaust ports (a first for production 250 motocross bikes, and one which promotes more symmetrical scavenging flow in the cylinder), semi-double-cradle frame, single-shock Pro-Link suspension and much more.

Although Honda wasn't the first to put a single-shock system on a production bike, the Pro-Link setup was the most innovative. It used a pivoting lower link, allowing mechanically progressive — also known as rising rate — wheel travel, independent of the shock spring rate. That made the suspension more supple over small bumps in the initial part of its travel, and stiffer to absorb big hits toward the end of its travel.

To the enthusiast press, the 1981 CR250R was a huge hit. Cycle magazine raved, "Honda built in power everywhere. The CR develops more horsepower at its peak than any 250 motocrosser Cycle has ever dyno tested...To build the CR's chassis, the Honda engineers again turned to their factory racers for the basic designs, and imitating the real thing paid off."

And Cycle World added, "The CR's engine is strong...We even got the hole shot in a pro race with it...The CR is great in corners...[and] also handles well over jumps...Honda's first-year production 250cc waterpumper has to be rated a success."

One trait that's stayed consistent about Honda's 250 motocrossers is that they have always set new standards for performance in the class, and forced all other manufacturers to step up their game in pursuit. That was true of the original Elsinore in 1973, the new case-reed, aluminum-frame 2002 CR250R and the revolutionary liquid-cooled CR250R of 1981.

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