Viking: I was trawling around the Internet, looking for RC17 related stuff, and found this review. All I can gather is that it’s from a magazine called ‘Motorcyclist’, and was written in 1984.
Fundamental to human nature is the need to proclaim ones individuality, perhaps because we most dread being just like everybody else. For the motorcyclist, this means starting with the basic mass-produced machine and spicing to taste. With the abundance of festoonery to choose from, touring riders have it easiest. By the time they’ve tacked the nativity scene to the dash and plugged in enough lights and chrome appendages to attain the Ned’s House-of-Neon look, their machines assume a persona all their own. Likewise, the profilers, following the form-above-all approach, rely on flash and frills to make their own individual statement.
But for the American sport rider, the pursuit of individuality is a bit more difficult. Sport bikes have never been so good, never so narrowly focused, never so purposeful as today. Aside from replacing tires and other fine-tuning, there really isn’t much that can be done to achieve major improvements. For the most part, these machines are stripped to their essentials, and in the form-follows-function doctrine, frills have no place. With fewer options available to the pure sport rider, mechanized individuality is difficult to come by.
It is no wonder then that sport riders with a craving for something different smuggle unavailables in from Europe. Continental contraband used to be leaps and bounds ahead of the American counterparts: they got the fireball stuff, we got the Milquetoast versions. With machines like Yamaha’s magnificent RZ500 prowling the autostradas, Europeans still have reason to sneer, but for the most part, the performance gap between here and there has been narrowed.
Our CBX750, bootlegged by a fast computer analyst who refers to himself simply as John, is a prime example of the times. Although not substantially better than the VF750 Interceptor Or the CB700 Nighthawk, its closest U.S. cousins, it is coveted in the U.S. because of its unavailability.
Purists will point to the CBX’s blacked-out ComStar wheels, satin black engine, Ferrari red paint and endurance-bred twin headlights and assume that the CBX is completely different from anything we have here. However, the European flair is an assemblage of very familiar components. Honda’s dedication to the hot-rod Nighthawk line and the Fed’s tariff intervention prevented the CBX from reaching our shores, but close scrutiny of the CBX reveals that it shares a design base with the CB700.
The CBX’s power plant was developed on the same drawing board as the CB700 engine. The horizontally split lower cases, altered to accommodate the CBX’s chain final drive, are otherwise identical to the CB700’s. Inside is a six-speed gearbox arranged just like the Nighthawk’s, albeit with substantially lower (numerically higher) gearset ratios. The new ratios work with the numerically lower chain final drive ratio to give the CBX a calculated 136-mph top speed.
Since the CBX750 is aimed more closely at the sporting rider than the Nighthawk and since it has an extra dollop of engine braking due to higher compression ratio and increased displacement, Honda fitted the engine with its one-way clutch mechanism used in the Interceptor models. But because Honda wanted to use the same right side engine case as on the Nighthawk and because the one-way mechanism takes up space within the clutch basket otherwise used for additional plates, the CBX has two fewer plates than the Nighthawk.
To bump the CBX’s displacement to 747cc, Honda engineers equipped the bike with a new forged crankshaft. A 3.6mm increase in stroke is responsible for the added displacement, allowing the same Nighthawk cylinder head to be retained. Since the Nighthawk uses rather large valves, 25mm intake, 22.5mm exhaust, Honda saw no reason to change them in the CBX. Nor has the proven hydraulic rocker-arm-actuated mechanism been altered in the CBX. Combustion-chamber shape is similar to that of the V-4 Interceptor series machines, and Honda has retained the 38-degree included valve angle, an arrangement said to be optimum for four-valve heads.
Like the Nighthawk, the CBX uses a shallow oil sump and employs the engine’s upper frame cradles as a reservoir. An aluminum cooler, nestled in the quarter-fairing just below the dual headlights, sends oil to the frame rails through rubber lines hidden within the bodywork. The same two-stage pump as on the Nighthawk circulates oil throughout the engine; the first stage pushes oil up through the left frame cradle, through the cooler and down the right frame rail to the sump. The second stage then propels oil through the engine. The shallow sump allows the engine to be placed lower and farther forward in the frame for increased front end grip.
The CBX’s alternator is positioned behind the cylinders and chain driven off the center of the crankshaft. As on the 700 Nighthawk S, the right end of the alternator has a small fan which draws in air and forces it through the windings, thus providing better cooling and higher electrical output.
Although the CBX750 has been touted as the fastest 750 money can buy in Europe, we were frankly less impressed. Since the CBX uses the same valve gear, camshafts and carburetors as the Nighthawk, the only real advantage the engine has comes from the increase in displacement. At the dragstrip, the CBX was only slightly faster than the 700cc Nighthawk1 posting a 12.10-second quarter-mite at 110.97 mph. Our Nighthawk, tested in February ’84 turned in a best run of 12.16 at 109.5 mph.
With such a slight horsepower advantage, the CBX exhibits its shortcomings more prominently. At low rpm, the CBX produces only slightly more power than the Nighthawk. The engine feels sluggish around town and forces the rider to maintain an active boot at the shift lever to pass slower traffic or zip around tight mountain roads. Not until the tach needle sweeps past 7500 rpm does the engine begin to breathe.
With the longer stroke came an increase in piston speed, which forced Honda engineers to lower the CBX’s red-line to 10,000 rpm (the Nighthawk red-lines at 10,700) in the interest of dependability. At peak revs, the CBX produces excellent horsepower, competitive enough to run with the fastest 750s we’ve tested. The problem is powerband and a lack thereof. Realistically, the ham-fisted rider has from 8500 rpm to just above 10,000 to work with. At 10,500 rpm, power begins to drop off and at 10,800 the ignition-controlled rev limiter puts an abrupt end to the party.
If you are capable, and willing, to work within the confines of the powerband, the CBX can indeed make good time, but in day-to-day living it is a less versatile machine than some other sporting 750’s. Pulling away from a stoplight requires a good deal of clutch slipping, far more than you would expect from a 750. More aggressive launches, like those required at the dragstrip, are tricky. Let the engine drop below 8500, and it falls into the dead zone. Keep it spinning high, and the clutch soon begins to emit its pungent displeasure. After only four hard launches at Carlsbad Raceway, the clutch, gave up altogether, but on less abusive days, the hydraulically activated unit served us well, offering predictable feedback and smooth operation. We also found that the CBX’s transmission was more positive and generally smoother than the Nighthawk and the VF750F V-4 gearboxes.
Quite honestly, the CBX750 is not much stronger than the smaller-displacement Nighthawk engine. So what makes the CBX so attractive to the European motor press? More than anything, it is probably because they haven’t ridden the Nighthawk. Secondly, it is because the CBX750 exhibits excellent handling characteristics. Aside from using the front downtubes as oil reservoirs, the CBX frame shares little with the CB700 Nighthawk. Unlike the Nighthawk, which utilizes a massive square-section backbone, the CBX has a large round spine supported on both sides by parallel secondary tubes that link to the main backbone through short perpendicular members. It is a fairly standard but very effective method of providing rigidity.
Out back, the CBX sports single-shock Pro-Link suspension, which called for a completely different rear frame section than on the twin-shock shaft-drive Nighthawk. Much like the VF750, the CBX’s shock is positioned vertically and compressed through progressive linkage located at the bottom of the shock. One convenience not provided by the Interceptor is the CBX’s plunger-type remote rebound-damping adjuster located just below the right side panel. The Interceptor uses a knurled wheel at the top of the shock, while the CBX links its adjuster to the damper via a small chain and allows you to alter the damping from the saddle. As on the Interceptor, preload adjustment in the single Showa damper is controlled by a remote air valve located just behind the right side panel.
Running gear is unique to the CBX. Both the Nighthawk and VF750 use Honda’s ComCast wheels, while the CBX rides on multi-piece, black ComStar hoops-18-inch rear, 16-inch front. Adorning the wheels are Honda’s highly effective four-piston calipers, which pinch spirally grooved 280mm discs. The CBX’s front discs are larger in diameter and feature more swept area than those fitted to either the VF750F or the Nighthawk. And the accompanying Japanese Dunlops are perhaps the stickiest OEM tires we’ve ever tried on any Japanese motorcycle.
A quick comparison of the CBX chassis’ vital stats gives insight into why the bike handles so well. Its 27-degree steering-head angle is a full three degrees steeper than the Nighthawk’s and 1.5 degrees steeper than the VF750’s. The CBX’s wheelbase, at 57.5 inches, is over an inch shorter than the VF750’s and 1.5 inches shorter than the Nighthawk’s. Though the Nighthawk undercuts the CBX’s wet weight by 15 pounds, the CBX maintains the same advantage compared to the VF750.
These figures translate into a machine that steers very quickly with the slightest provocation at the handlebars. Steering is neutral at low speeds, when the Interceptor has a tendency to fall in. Some of this low-speed neutrality is no doubt due to the fact that the CBX carries the bulk of its weight, the engine, much lower than the tall Interceptor. As speed increases, the CBX remains neutral, able to change direction in mid-turn with ease, and perfectly willing to be ridden deep into a turn while braking heavily without much tendency for the front end to push to the outside, tuck under or stand up. Even the excellent Nighthawk front end lacks the surefooted consistency of the CBX.
Coupled with the short wheelbase, the CBX front end inspires the rider to push his limits further and more frequently than he would on the VF or Nighthawk. The excellent Dunlops surely play a large role in this, but the superb chassis deserves the most credit. This machine steers as quickly and accurately as any 750 available in the U.S. It can be flicked hard from side to side and makes transitions in less distance, with less effort at the handlebars and with fewer adverse side effects than all but a handful of the best sporting machines we’ve tried.
On a fast road, where the rider has the best chance of keeping the engine singing, the CBX runs with more powerful ma-chines because it maintains such high cornering speeds and is not limited by such considerations as cornering clearance. It takes a rider with few earthly attachments to drag the footpegs, and even at such impressive cornering angles, the stock Dunlops are beyond reproach.
Braking performance is as advertised – strong, sensitive, predictable and able to be fully utilized with a minimum of effort at the controls. Here again, the Dunlops allow the binders to be exploited in panic situations without adding an extra degree of uncertainty.
During more sensible jaunts on tighter roads, the CBX is pleasant enough but doesn’t attract unusually high praise. Though the suspension is acceptably compliant, we would opt for a bit more rebound damping in the rear. Cresting a hill under acceleration causes the suspension to extend too quickly and interrupt traction. Likewise, hitting an especially sharp bump prompts the rear end to kick up rather suddenly. This is partially because the rear suspension is softly sprung and relies heavily on compression damping to resist bottoming. Hydraulic resistance is not as effective as a spring in this situation, and the result is a damper that can’t react quickly enough and responds harshly.
The front end is better equipped to handle bumps, mainly because the 39mm Kayaba fork offers a wide variety of adjustments. Rebound damping has three possible settings, varied by turning a knurled knob at the top of the right leg. The left leg offers four-way TRAC anti-dive adjustment by spinning a dial on the TRAC unit itself. The left leg also has a filler for air pressure and links to the right leg through a balancing tube. A strong, stamped-aluminum fork brace ties the whole operation together and prevents flexing.
At the maximum preload and rebound-damping settings, the fork responds well to fast roads, while the TRAC system prevents excessive nose dive. If we were to nit-pick, we would ask for a bit more rebound damping up front as well because the front end tends to feel a bit skatey under hard acceleration, probably because the fork extends rather quickly. Conversely, this rapid extension allows the fork to soak up anything the road can throw at it in most situations.
Apparently, the Europeans do most of their riding on fast, sweeping roads, or at least Honda intended them to, because that’s where the CBX really shines. But trolling along the Interstate at 55 mph is no free lunch on the CBX, even with the suspension set up softly. The suspension is surprisingly harsh in response to small bumps and freeway expansion joints. This complaint, of course, is academic in Europe where few roads have expansion joints or rail grooves, which the Dunlops follow like lemmings.
One very familiar aspect of the CBX is its seating position. Like the VF750 Interceptor’s, it is roomy and features a soft, albeit narrow, seat. Footpegs are positioned more rearward on the CBX and about an inch higher. Europeans are also willing to forgo a bit of highway comfort in the interest of front-row seating for the mad canyon dash. We spoiled Americans like a little more leg room and higher handlebars. We must admit, however, that the CBX’s small fairing does an excellent job of deflecting the wind at low speeds and lets just enough of the blast hit the rider at highway speeds to hold him upright and take pressure off his arms.
The CBX is also one of the smoothest machines we’ve ridden. Only at peak revs does enough vibration reach the rider to be considered annoying; and this despite the fact that only the front engine mounts float on rubber dampers. At all other speeds, the CBX is impressively smooth, with only a tinge of vibration passing through the rubber footrests.
High on the list of favorite amenities are the CBX’s excellent switches, loud horn and searing headlights. These dual headlights throw a mean beam at night and light up far more of the roadway than you can possibly take in. Switched to high beam, the quartz headlights are blinding and provide the kind of nocturnal vision American machines sorely lack.
We also noticed that the CBX was exceptionally well constructed. All panels flowed nicely from one juncture to the next with no gaps in the bodywork and no extraneous plastic do-dads to fill dead space. True, the CBX comes with those tacky alloy falsies that give the illusion of velocity stacks, just like the Nighthawk, but for the most part, we were impressed with the quality of fit and finish.
Like so many others who view the European unavailables as far and away superior to what’s sold here, we were initially expecting the CBX750 to be heaven on wheels. It is marginally faster than the Nighthawk and offers superior steering characteristics, it does handle better in many situations than the VF750 Interceptor, and it is comfortable enough and offers the sort of mannerisms so appealing to more casual riders. But unlocking its secrets takes a rider who is sufficiently proficient and willing to overcome its shortcomings. And we already have motorcycles that fit that bill in the U.S.
The true attraction of the CBX can’t be measured in hard performance figures because it is not substantially better than what is readily available. Its attraction can only be calculated by the number of people who don’t own one, and the greater that number, the more compelling the CBX750 becomes.