End of the Line

The CBX750 was Honda's last air cooled in line sportsbike. Roland Brown takes a trip back in time - to Africa.

THE CBX750F was in good company on Honda's 1984-model launch in South Africa, and it provided me with the most memorable ride of the trip. Darkness falls unexpectedly suddenly on a first visit to Africa. More than 20 years later I can still vividly recall the thrill of blasting for mile after mile through the warm night air, chasing a group of VF1000F and VF1000R V4s, with my way illuminated by the brilliant twin headlights of Honda's stylish new straight four.

If that was the highlight of the launch, the CBX also provided an even more spectacular low point, though thankfully I wasn't directly involved this time. Instead, I rode past with pulse racing just after another journalist had locked his front wheel when braking at the end of the Kyalami circuit's main straight, crashing at high speed and leaving a huge diagonal mark of red paint going up the trackside concrete wall. Fortunately, he walked away from the wreckage.
So one way or another the CBX (which had nothing to do with the six-cylinder CBX1000, by the way) certainly made an impact on its introduction. The transverse four had stood out in another way, too, because it was very much a loner in Honda's line-up. That 1984 South African launch also introduced the VF500F, which joined the two new VF1000 models plus the existing VF750F in the range. Amid all those V4s, the CBX was effectively Honda's final attempt at making a cutting-edge sports bike using the aircooled, transverse four-cylinder format that dated right back to the CB750 of 1969.
Japanese engine technology had advanced a long way in the 15 years between the two fours. Honda had already adopted a dohc, 16-valve layout, to which the CBX added a new twist with its maintenance-free hydraulic tappets. Its motor had been developed from the similar unit of the US market CBX650, bored and stroked to give capacity of 747cc from dimensions of 67 x 53mm. Peak output was a claimed 92bhp at 9500rpm, slightly up on Honda's own VF750F, and also on straight-four rivals such as Kawasaki's GPz750 and Suzuki's GSX750.

The CBX stood out from the crowd, thanks largely to sharp styling that blended its half-fairing neatly into the tank, which in turn joined the seat unit. There was a matching belly-pan below the engine, which was narrow because its alternator was situated above the gearbox. But Honda's stylists lost credibility with the bike's plastic fake velocity stacks, an even more feeble attempt at deception than the silver-painted steel frame tubes that were popular in the mid-'80s.
This model did not suffer that fate, as its steel frame (which had a large-diameter spine under the tank) was black, and notable mainly for holding oil in one of its downtubes. Other chassis parts were classical mid-'80s fare: a 16-inch front wheel, air-assistance for both the front forks and Pro-Link rear monoshock, and a trio of disc brakes with twin-piston calipers up front, and Honda's TRAC anti-dive system. Other features included a large instrument panel holding a speedo, rev-counter and, in a third round dial, gauges for fuel level and volts.

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Mad Yank on a
Monowheel

Kerry McLean went so minimalist he built a bike with only one wheel. Rod Gibson got a closer look..

THE concept of a single wheeled motorcycle is one which has intrigued designers through the ages. Various people have experimented with the format but the idea has never really caught on, partly because the single wheeled layout is inherently unstable without significant design and development, and the end result has never really been enough to justify the time and resources required to make it work. So the monocycle, or monowheel, has remained a novelty on the sidelines of motorcycle development history. Until Kerry McLean came along, that is. Kerry is no stranger to oddball engineering projects, having spent much of his formative years in Michigan building Hot Rods, Trikes and jet propelled bicycles. When he first started experimenting with single wheeled motorcycles back in the mid seventies he found the problems inherent in the design were far from from insoluble, and over the next thirty years devoted much of his spare time into making the concept work. The result of all this work is a handful of machines built by Kerry, each one carefully hand made and each one taking development further as he's learned lessons along the way.

Monowheels present a number of challenges to the designer, and several compromises have to be made to get everything to gel together into a functional machine. The first problem is stability. The monowheel depends on gyroscopic effect to keep it upright. As gyroscopic effect is proportional to rim speed, smaller diameter wheels become stable at lower speeds than large ones. Tall wheels feel top heavy to ride, and present a considerable challenge to the rider to get moving fast enough to find stability. Adding low-down weight can counteract the top heaviness to some degree, but weight can create its own problems.

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