Honda’s Throwback: 1978 Honda CX500

By Margie Siegal
Published on February 12, 2015
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In 1979, Honda offered the CX in three versions. There was the standard CX500 (pretty much the same as the 1978 version), the Custom (peanut tank, hi-rise bars) and the Deluxe.
In 1979, Honda offered the CX in three versions. There was the standard CX500 (pretty much the same as the 1978 version), the Custom (peanut tank, hi-rise bars) and the Deluxe.
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1978 Honda CX500
1978 Honda CX500
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1978 Honda CX500
1978 Honda CX500
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The longitudinally-mounted V-twin has the crankshaft in line with the frame as on a Moto Guzzi.
The longitudinally-mounted V-twin has the crankshaft in line with the frame as on a Moto Guzzi.
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The 4-valve heads are skewed 22 degrees to tuck the carbs in tight out of the way of the rider’s knees.
The 4-valve heads are skewed 22 degrees to tuck the carbs in tight out of the way of the rider’s knees.
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The 4-valve heads are skewed 22 degrees to tuck the carbs in tight out of the way of the rider’s knees.
The 4-valve heads are skewed 22 degrees to tuck the carbs in tight out of the way of the rider’s knees.
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Owner Larry Cargill restored this Honda CX500 to have as a show bike, but he has another CX500 that he rides frequently.
Owner Larry Cargill restored this Honda CX500 to have as a show bike, but he has another CX500 that he rides frequently.
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Owner Larry Cargill restored this Honda CX500 to have as a show bike, but he has another CX500 that he rides frequently.
Owner Larry Cargill restored this Honda CX500 to have as a show bike, but he has another CX500 that he rides frequently.

1978 Honda CX500
Claimed power: 48hp @ 9,000rpm
Top speed: 111.9mph (period test)
Engine: 496cc liquid-cooled OHV 80-degree V-twin, 78mm x 52mm bore and stroke, 10:1 compression ratio
Weight (wet): 481lb (219kg)
Fuel capacity/MPG: 5gal (19ltr)/40-50mpg
Price then/now: $1,898 (1978)/$1,500-$5,000

Once upon a time, a motorcycle was transportation. Faster than a streetcar and more reliable (and cheaper) than a horse, motorcycles were bought by thousands of people who used them to get to school or work. Delivery services and police departments relied on motorcycles to get where they wanted to go quickly and economically.

Most motorcycle manufacturers got started building reliable, economical get-to-work bikes. Honda was no exception. Yet as the 1950s gave way to the 1960s, in developed countries like the U.S., England and Europe, motorcycles stopped being transportation, morphing into a Lifestyle Statement instead. Bikes sprouted exotic bodywork, multiple cylinders, overhead cams, high handlebars and fancy seats. Advertisements stopped mentioning miles per gallon and started crowing about quarter-mile times.

Yet in the late 1970s, Honda, then (and still) the largest motorcycle manufacturer in the world, decided to return to its roots and produce a reliable motorcycle aimed at the get-to-work crowd. Honda’s brief called for reliability and low maintenance, and up-to-date technology. The CX project was headed up by Shoichiro Irimajiri, who designed Honda’s 6-cylinder road racer in the mid-Sixties. After two prototypes were designed and built, one displacing 350cc and another 500cc, the decision was made to make the new model a 500. The CX was given liquid cooling, a 5-speed gearbox, constant velocity carburetors and shaft drive. Surprisingly, it was not given an overhead cam engine.

Design considerations

The decision to use an overhead valve design with pushrods on an otherwise very modern machine may seem a little strange, but was compelled by the longitudinally-mounted, 80-degree V-twin design, which had the crankshaft in line with the frame as on a Moto Guzzi. To accommodate this, the 4-valve heads were skewed 22 degrees to keep the carburetors from banging the rider’s knees. That skew would have made it very difficult to use overhead cams, so it was back to pushrods. The pushrods were short and hollow, and an exceptionally (for then) over-square bore and stroke of 78mm x 52mm let the engine rev to 10,000rpm. Mated with a free-flowing intake tract and large carburetors, the engine had good volumetric efficiency.

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