Honda CX500 Turbo

The CX Turbo was not happenstance, but a direct response to other currents shaping the market in the early 1980s. Yamaha was battling Honda for supremacy in the motorcycle market, and Honda was fighting back. Honda management decided to show the world that the company was capable of a design and engineering feat that was far ahead of what any presumptuous rivals could do. That showpiece was the CX500 Turbo.

Normally, Honda exhibited new motorcycles to the press only when the development work had been completed and the bike was almost ready for sale. Although nowhere near ready for the market, Honda put the CX500 Turbo on display at the 1980 Cologne International Motorcycle Show and afterward had it on exhibit at the Honda Research and Development Center in Tokyo. Match that, Yamaha!

Turbo background

A turbocharger is used with an internal combustion engine to provide more power, typically above a specified RPM. The extra power is provided by the engine’s exhaust. Exhaust gases rushing out of the engine under pressure spin a turbine, which spins a compressor, which in turn compresses the intake air charge over atmospheric. Of course, what sounds fairly simple in theory often turns complex in practice. Honda’s achievement lay in applying the turbocharge concept commercially, producing a reliable motorcycle able to cope with a variety of conditions.

In motorcycling, the turbo concept began with experiments by race teams looking to get more combustible mixture into engines faster. Most of the GP race teams of the Thirties tried supercharging, a different means to reach the same result. In the 1970s, drag racers installed turbo kits in their motorcycles, and automobile manufacturers began to research turbocharging as a way to get extra performance out of a small engine. Turbo kits began to migrate to street motorcycles, and Kawasaki America came out with a limited production turbo in 1978, the Z1R-TC (see 1978 Kawasaki Z1R-TC: Turbo Power). That bike was not completely successful.

Honda’s turbo

The basis of the CX Turbo was a proven slogger, the CX500. Powered by a V-twin that was often derided for looking like it came out of an air compressor, the CX500 was the sort of bike you bought to get to work every day, no matter the conditions. Bombproof it was, exciting it was not. As a platform for innovation, however, the CX500 had potential. It had liquid cooling, shaft drive and mag wheels. The first V-twin ever built by Honda, it had four valves per cylinder, fed by constant velocity carburetors. The 1981 version of this bike had Honda’s innovative Pro-Link monoshock rear suspension, which moved weight under the rider and featured more progressive damping.

Honda took the CX and re-engineered it into the Turbo. Reasons for choosing this bike as the platform for turbocharging included its liquid cooling, which enabled the engine to cope with the increased heat of turbocharging. Another was displacement — midsized bikes had quite a following in the late Seventies. Kazuo Inoue, the top man in Honda’s R&D department at the time, and the leader of the Turbo project, told Cycle Guide, “We set out to make a little motor and measure it by the performance standards of a big bike.”

According to Inoue, the project was made more difficult by the CX’s V-twin configuration and its smaller displacement. But Honda was able to make the CX500 Turbo work despite the difficulties, producing more than 230 patents for the components in the process. The turbocharger was built to Honda’s specifications by IHI. Honda mounted it in front of the engine to take advantage of available space and additional air-cooling. It was one of the first production bikes to feature computer-controlled fuel injection.

The front fender employed small scoops to direct more cooling air to the engine, while air-assisted front forks and dual front discs, each with twin-piston calipers, took care of business up front. The front end used Honda’s innovative TRAC (Torque Reactive Anti-dive Control) anti-dive system, which linked the brakes to the fork valving: As the brakes were applied, the calipers pivoted, pressing on fork valves to restrict compression damping. The wheels featured the ComStar rib pattern, with a wind tunnel-tested fairing dressing the bike.

After more than a year of letting the public peek at the project, the CX500 Turbo finally arrived at dealerships in the spring of 1982. Cycle World got its hands on a production bike for its April 1982 issue. Much of the article was devoted to the complex systems making up the new Honda. Basically, air was routed from the front of the CX though an oiled foam air filter and then into the compressor part of the turbocharger. From the turbo mounted in front of the engine, air traveled to a plastic box (called a surge tank), and then through reed valves and intake tubes into the cylinder head.

Fuel passed through a fuel filter before being pushed under pressure by an electric fuel pump, where it was fed to fuel injectors that released a precisely calibrated flow of fuel to the intake tubes. The whole operation was controlled by a mini computer in the tailpiece, which got continuous feedback from multiple sensors. Fail-safe systems were built into the computer so that even if several sensors failed, the bike would run well enough to make the trip to the dealer.

Cycle World staff either loved or were irritated by the Turbo. On the plus side, it was a comfortable, reliable sport tourer. The fairing worked well to keep the rider out of the airstream, the seat was comfortable and the handlebars were in the right spot for most testers. Vibration was low and controls, except for the somewhat heavy shift lever, were easy to operate. The horsepower boost came on at about 4,000rpm and, for many testers, was FUN. Detractors of the Turbo cited its weight, not-great low-speed handling, lack of low-end power and difficulty controlling the motorcycle when the boost came on strong.

Other magazines tested the Turbo, and came away with basically the same reaction. Road Rider noted high fuel consumption and the lack of a fuel reserve, but the editors also said the bike’s turbo boost was pure, grin-producing fun. “The Turbo works well as a sport bike on back roads filled with long, fast, sweeping turns,” Cycle said. “The Turbo’s precise steering is just a touch heavy,” Cycle continued. “On fast winding roads, the CX500’s power characteristics make the bike difficult to ride hard. The Honda’s turbo lag delays engine response by a second or two … sport riders must learn a new riding technique.”

Winds of change

There was another cold wind blowing in the U.S. besides the end of the Baby Boomers’ summertime and the clash between Honda and Yamaha. The economy was suffering and a steep recession took hold from July 1981 through November 1982, and the bottom dropped out of the motorcycle market. Honda and Yamaha had been exporting lots of bikes to the U.S., and to get unsold inventory out of warehouses, both were selling motorcycles for rock bottom prices. Threatened, Harley-Davidson petitioned the International Trade Commission for relief, resulting in the ITC imposing tariffs on 700cc or larger Japanese motorcycles.

Despite the gloomy economic outlook, Yamaha introduced its own Turbo shortly after the launch of Honda’s Turbo. Kawasaki and Suzuki were not far behind with their own offerings, with the KZ750 Turbo and XN85D, respectively, introduced for 1983. All of these turbocharged motorcycles must have been extremely expensive to build, but for the moment, the bean counters held off.

For 1983, Honda punched out the CX Turbo from 497cc to 674cc and raised the compression ratio somewhat (7.8:1 versus 7.2:1) for an increase in power from a claimed 82 to 100. This would prove to be the CX Turbo’s last hurrah: 1983 was basically the end of the road for the turbo wars. The motorcycle market was not improving, and the bean counters at Honda (and the other factories) finally got the upper hand. Honda, Yamaha and Suzuki dropped their turbos, with only Kawasaki holding out, producing their turbo until 1986.

Ownership is everything

Well-known collector Zeki Abed is a landscape architect, a connoisseur of classic Japanese motorcycles and the third owner of this CX Turbo. “The first owner bought the bike and never rode it. He let it sit for 15 years and then sold it to the second owner, who rode it some and then sold it to me. It was totally stock, and had never been dropped. I haven’t had to do anything to the bike besides clean it and replace the fluids,” Zeki says.

Motorcycle journalist Clement Salvadori has said the CX500 Turbo deserves to be in an industrial art museum, and Zeki agrees. “It’s the look! The overall design was cutting edge — so much attention to detail. Fit and finish at every angle you look at on this bike is excellent.” Zeki continues, “The CX Turbo was one of the most technologically advanced bikes of the day. As a designer, I really appreciate some of the design elements, such as the integrated blinkers, the beautifully formed body, the anti-dive fork lowers and the seat that wraps into the tank. The gold anodized wheels are a beautiful piece of technology. The dash gives the feeling that you are in the cockpit of an airplane.”

Zeki says he breaks out the Turbo every two or three months for a ride, and he is always impressed by its reliability. “Nothing goes wrong — I just have to keep the battery charged, and it starts on the first touch of the button.” He says the Turbo is a little top-heavy, but likes the feeling that “you are sitting more in the bike, instead of on top of it. You also feel that there is a lot of bike in front of you, with the large, wide tapered tank.

“It’s basically a cruising bike,” Zeki continues. “Once you get out on the freeway, or on a country road with big long sweeping turns, the turbo is in its element. It’s an open-roader. It’s not like the Kawasaki turbo, which is more like a jet. The Honda is more like a turboprop airplane. It’s a gentleman’s turbo. It just cruises along and then you crack open the throttle, hit the turbo response — you just roll on and it kicks up and goes galloping away. I am just fascinated by the machine. It’s sexy, infectious to look at — it’s candy to the eyes.” MC