1970s Motorcycles: Honda’s Six-Cylinder CBX

In the Mid-’70s, Honda Needed to Reassert Its Engineering Dominance and Kickstart Motorcycling Passion. The CBX Did Both.

1970s, Honda CBX
1979-spec Honda CBX with Senior Editor Zack Courts aboard.©Motorcyclist

As intense and successful as the early 1970s were for the Japanese motorcycle manufacturers, and as powerful as Honda became during that period, it's a bit strange to say that a third of Honda's lineup had become stodgy and reasonably uncompetitive by 1975. After massive successes like the astounding CB750, the Elsinore dirt bikes, and the innovative three-wheeled ATC, Japan's engineering powerhouse seemed to have lost the plot.

Few thought it could. But Honda had.

By that point, Kawasaki's stunning 903cc Z1 had made a non-issue out of the CB750—a bike Honda had done nearly nothing to in the six years since its introduction. Yamaha sold its giant-killer RD350 like there was no tomorrow, and by '76 there'd be an even better RD400. The bicentennial would also bring the GS750, a motorcycle that would make folks forget about Honda's SOHC 750.

Honda CBX six cylinder engine on May 1978 Motorcyclist Magazine cover


May 1978 Motorcyclist: We were split on the CBX when it debuted, as was the public. But the impact it had on Honda's technology and reputation boosted Big Red into the 1980s with rocket-like thrust.©Motorcyclist

Honda introduced the GL1000 in ’75, of course. But its automotive-esque design—an indicator of Honda’s push toward what would be a world-class automotive manufacturer—shouted “tourer” a lot more loudly than “performance,” so it barely nudged the excitement meter. At the time, many felt that motorcycle division needed a serious shot of adrenaline, a flagship machine that would make people take a deep breath and say, “Whoa!” Fortunately, the men in the big office—Soichiro Honda and division president Tadashi Kume—knew the score and knew who to tap to make it happen: Shoichiro Irimajiri, Honda’s head of R&D.

Iri, as he was known, was already a bit of a legend at Honda. After graduating from Tokyo University in 1963 with a degree in aeronautical engineering, he joined Honda after finding no work in the aviation business. “Honda was my second choice,” Iri said later with a smile. Almost immediately, he began developing Honda’s Grand Prix racers and, understanding that more cylinders were the only way four-strokes could compete with lightweight two-strokes, helped design a range of exotic, multi-cylinder racers that quickly became legendary: the 1964 RC115 (a 50cc eight-valve twin that revved to 21,000 rpm), the ’65 RC147 (a five-cylinder 20-valve 125 that revved to 19,500), and the immortal RC165, a 24-valve, six-cylinder 250 that redlined at nearly 15,000 rpm. (Hold that thought…)

Honda CBX, side view
In 1978, Motorcyclist editor Dale Boller said, "We need this motorcycle like we need a hole in the head. Its single greatest virtue—raw speed—can't even be experienced legally."©Motorcyclist

A decade later, while America celebrated its bicentennial, Iri and his team developed a new plan for Honda’s excitement-starved streetbike lineup. It included a couple of new twins to bolster the middle of the lineup (a vertical twin and a transverse vee that would become the CX line) along with two flagship concepts. One was an all-new CB750, which would become the twin-cam, 16-valve F-model introduced in late ’78. The other would be a sporty, performance-oriented open-classer… But what that concept comprised, they did not yet know.

1979 Honda CBX with Motorcyclist Senior Editor Zack Courts riding
1979-spec CBX©Motorcyclist

The obvious direction was a high-end CB1000 based on Honda’s successful RCB endurance racer. But Iri and his team knew that a 1,000cc four with two cams and 16 valves—as good as it would likely be—could be seen as merely “catching up,” not setting the bar a notch or three higher, as they very much wanted. And that’s when the idea for something completely different surfaced—something unique and stunning, maybe even something that recalled Iri’s days in the GP trenches.

Honda CBX gauges and dash
The instrument cluster was known during development as the “Mickey Mouse” panel.©Motorcyclist
Honda CBX tail section
Tail cowl was a fortunate addition late in development; the CBX looked much tamer without it.©Motorcyclist

Very little is known of the discussion that transpired after the very first mention of a six-cylinder production streetbike based on that crazy, 250cc RC165 racer. We can imagine the excitement somewhere in Honda’s then-new R&D facility in Asaka that day and do know that Project 422 was quickly green-lighted. Interestingly, upper management also approved the development of the 1,000cc four project, which would run concurrently with Project 422. The thinking here was based purely on competition: Let’s see how each bike works at the prototype stage and then make our decision on which to actually produce.

Honda CBX assembly line in Japan
Honda assembly-line workers installing a bank of six carburetors at the Sayama factory in mid-’78. Note the way the carbs angle toward the center.©Motorcyclist

A pair of teams—one for each of the two open-class concepts—quickly got to work. The styling team for the six-cylinder project, headed by Minoru Morioka and Yoshitaka Omori, began with rough sketches, which ran the gamut from an almost CB750 lookalike to a futuristic jet-fighter theme. Besides a bit of semi-integrated bodywork and one attempt at a small cockpit fairing, the shapes were familiar. Slowly over the summer months the shapes began to morph into ones we recognize now: the dramatically sculpted tank, wide at the front and narrow in back, and that bold, waisted engine leading the way without frame tubes marring the view.

Honda CBX pre-production sketch
The CBX’s final sketch from 1977 is reasonably close to the bike’s actual look.©Motorcyclist

In truth, the first mock-ups had downtube frames, engineers using the reasonably stiff and functional cage design as a starting point. It had worked on the RC; surely it would be okay on the streetbike. But two considerations removed it from consideration: One was aesthetics. That engine, which Mr. Honda himself insisted must be sexy and beautiful in addition to being powerful, had to be seen. “Mr. Honda wanted the most powerful engine,” Morioka remembers, “and at the same time paid enormous attention on how the engine looked.”

Honda CBX mockup
The first mockup, assembled in ’76, was homely, but it was a start.©Motorcyclist

Another problem was packaging. The new engine’s narrow cylinder pitch and the number of pipes exiting in such a small space made it extremely difficult to use traditional downtubes without serious angling of pipes and/or tubes, which would spoil the look. So fairly early, engineers incorporated a downtube-less design, where the engine would bolt to the frame from above and in back. “If those tubes had to be bent,” Omori says, “it would look like hell. That’s why we changed it.” Repercussions would follow, though not for months.

Things moved quickly during the summer, each team motivated by excitement as well as pressure from above to finish quickly, as both open-class projects had been fast-tracked from the very beginning. Iri’s knowledge of the RC165 project helped the powerplant team tremendously; he’d been there before, knew the ins and outs of such a wide and powerful engine, knew where problems would crop up, and knew how to fix them.

Honda CBX engine
The CBX Six was built for romantics, for people with soft spots in their hearts for mechanical maximum expressions.©Motorcyclist

By early 1977, stylists had produced sketches of what higher-ups would confirm as the Six’s final look. Styling mules were assembled with as many pre-production pieces as possible, as well as sand-cast engine parts. The visual results were decidedly mixed; the bike’s front half was strong and sexy, but the back was lacking something. That something, according to Omori, was a tailsection.

“At that point,” Omori says, “we were already close to the final version, [but there was no] tail cowl. The R&D director said to me, ‘This bike has no punch. Can you do something with it?’ I then asked CB750F designer Hitoshi Ikeda if I could try something, and he agreed. I ended up making a winged tail cowl. Ikeda asked if it was a gimmick, so I asked Shinji Kakatani of the Blue Helmets [Honda’s in-house race team], who said it would be effective. When we contacted Mr. Morioka, who was away in Europe, for approval, we learned he was working on the same thing for the 750F!”

Prototype testing was by now in full swing, and Iri was worried. “The biggest problem [with the CBX] was the weight,” Iri says. It had climbed to more than 450 pounds. “How to [reduce weight] was our biggest headache.” The bike would soon go on a strict weight-loss regimen, getting aluminum triple clamps and handlebars and other lighter bits. But it still ended up being nearly 600 pounds full of fuel in production form.

With the CB1000F prototype also up and running (the bike would eventually become the CB900F), it was time to decide. “[The 1000F] was extremely light,” Iri remembers, “and actually faster than the CBX, [especially] on the track. But we felt there was something exhilarating and exciting about the Six that was lacking on the four-cylinder bike. The rumble of the exhaust, the feeling of acceleration, the vibration, its smooth, high-revving engine. [There was] something in the CBX that could not be measured, [and that] made it a very sexy machine.

Honda CBX, sport-touring version
Honda produced sport-touring versions of the CBX for ’81 and ’82.©Motorcyclist

“There was a big discussion which machine to go with,” Iri continues. But based on Honda’s desire to build “a totally new superbike, one unlike any that had been made before, we chose the CBX.”

Still, pre-production handling problems persisted, all connected to weight and frame-rigidity issues. According to Ian Foster's amazingly detailed new book The CBX, (from usedcbxparts.com or mrcbx@att.net; $50) Iri discovered the depth of the handling issues when larger and more aggressive American Honda test riders rode the bikes at Suzuka. The lighter Japanese riders hadn't had the same problems. "This opened our eyes," Iri says in Foster's book. "Honda knew how to make engines, but in our minds frames were not that important." Iri explained that, in those days, frame engineers weren't talking to the engine guys, and he realized after the CBX's release that Honda needed to find a way to make more rigid frames as its engines got more powerful.

In late 1977, a handful of pre-production machines were prepared for testing and some early press coverage. In November, Honda invited some American dealers and European editors to Suzuka, Honda's primary test venue at the time. One of those machines made its way to Southern California in October for Cycle magazine to sample exclusively, the results of which made it into the magazine's February 1978 issue. Cycle editor Cook Neilson was flabbergasted by the bike's performance and chutzpah.

1979 Honda CBX
Our photo model is a ’79-spec CBX fitted with the available-from-Honda (and standard in Europe) sport kit, which features lower-than-stock alloy bars and rearset pegs.©Motorcyclist

“We are at Willow Springs Raceway this dark, sharp morning to see, feel and ride a motorcycle which much is rumored but nothing is known,” Neilson wrote. “Four days later—two at Willow Springs, one at the Webco dynamometer, and one split between Orange County Raceway and American Honda—we came to believe that in the 1,047cc, 24-valve, double-overhead-camshaft CBX-Six, Honda had the Haymaker it wanted. There are flaws here and there, signs of haste and certain ambiguities. But the objective—to build the fastest production motorcycle for sale anywhere in the world—has been met. The bike is more than fast; it is magic.”

The American Honda dealers in Japan for that November introduction at Suzuka were treated to some magic, too, but of a cinematic variety. At a local theater the night before they learned of the CBX’s existence, Honda showed a film that made many of them literally jump for joy.

“It was probably the most excited I’ve ever seen dealers,” longtime Honda man Jon Row remembers. “The sequence on screen was a pan shot, starting at one side of the engine, shot from the front, looking at the exhaust pipes. As the image moved left to right, you saw the cylinder block come into view, then one head pipe, then two, and then three. And when dealers noticed extra space for the cam chain after the third pipe, and realized Honda had built a Six, the room just exploded! Some were standing on their chairs. It was nuts! They’d been getting beat up by the Z1 for so many years, and this was retribution. Honda needed something exciting, and this did the trick, at least emotionally.”

1979 Honda CBX with sport kit
The CBX sport kit is virtually unobtanium now.©Motorcyclist

We were divided in our opinions. Motorcyclist editor Dale Boller said, "We need this motorcycle like we need a hole in the head. Its single greatest virtue—raw speed—can't even be experienced legally." Staffer Brad Zimmerman, in that same May 1978 issue, respectfully disagreed: "While parked it evokes an atmosphere of 'just try me,' challenging your ego to jump aboard for an acceleration thrill. I would buy our testbike immediately. But Honda won't sell it because it's a prototype."

Press reports were generally positive, but early sales were not brisk. “It was a combination of things, I think,” remembers Bob Troxel, who worked at a Wichita, Kansas, Honda/Kawasaki shop during the 1970s. “Folks were curious and interested, and we sold some. But generally speaking, the CBX was seen as big, heavy, expensive, and complex. I love them and own an ’82 still. But it just didn’t connect well enough with customers for it to be a sales smash.”

The CBX, in its initial guise as a stripped-down sporting machine lasted just two years, 1979 and ’80. The ’80-spec machine differed quite a bit from the unfiltered original, too, with less power (98 ps, due to new German regs), an 85-mph speedometer (US DOT silliness), black Comstar wheels, an air-assist fork, a 20-percent-higher capacity oil cooler, adjustable-damping shocks mated to a swingarm with better bushings, glossy side covers, a tailsection compartment, and some other detail changes. For ’81 and ’82, the CBX morphed into a serious sport-tourer, with more midrange, a slick Pro-Link single-shock rear suspension system, hard bags, a big fairing, and a whole different demeanor. And like its predecessor, it sold slowly.

Still, it's pretty hard to argue that the CBX didn't achieve what Honda needed at the time. It, along with the CB750F, CX500, and CB1000F prototype projects, yanked Honda out of its tech-less lethargy, proving to itself and the world that it still had the ability and foresight to build exciting motorcycles. Honda still had it. One could also argue that the CB900F, CB1100F, and the liquid-cooled, V-4 Sabres, Magnas, and Interceptors that followed benefitted from the momentum generated by the CBX.

Cycle's Cook Neilson summed it up pretty well: "The CBX," he wrote, "rubs hard against the acceptable limits of mechanical intricacy and weight, and anyone with a pragmatic view would take issue with both the bike's complexity and its total performance concept. But the Six was not built for pragmatists. It was built for romantics, for people with soft spots in their hearts for mechanical maximum expressions, for people whose specific reasons for motorcycling match the CBX's specific reasons for being built. The CBX is an immensely flattering bike with perfect elegance and total class, and history will rank it with those rare and precious motorcycles which will never, ever be forgotten."

Not much chance of that.