British Magazine ‘Motorcycle International’ ran this article in one of their 1990 issues. Thanks to list members Robin Bennet and Darren Moody for the article and the pictures.
The pictures are all black and white (ie, greyscale). The pictures sent by Robin had been scanned at high resolution and scaled down, whilst the pics from Darren where huge to start with, and I had to scale them down. I then took the best pictures from both to make the article.
So if you want to complain about the picture quality, moan at Daz, Robin or myself. But be warned – I’ll challenge you to do a better job! Click on the picture to view slideshow.
|Motorcycle International Test|
The Honda CBX750 was a bike that broke new ground at the forefront of the technology race, and then disappeared without trace. It was a bike that was described as having ‘more new features than the Odeon Leicester Square’ when it was launched back in 1983 but which was only on sale for three years before being phased out. According to tired old hacks (no names, no pack drill, eh Rick?) it also brought a breath of fresh air to a class that at that time (the early ’80s) was dominated by not very interesting dohc 750 across-the-frame fours. In fact the CBX was really the missing link between the old guard 750s and the new generation of supersport 750s.
It all started back in 1983, when out of the blue Honda introduced the CBX750 alongside the VF750 as a replacement for the faithful old CB750 which by then was beginning to show its age. The VF750 was considered to be the hot-shot 750 in the range so Honda brought in the CBX to act as a ‘cooking’ 750. In the event the CBX turned out to be a better bike and actually sold almost as well as the disaster-prone VF. In fact the CBX was really the last of the ‘cooking’ Honda 750s because when it was phased out in 1985 it was replaced by the VFR75O and that was the end of the Honda in-line four cylinder 750 (unless you count the Japan-only CBR75O).
While based very loosely on the old CB75OF the CBX is really a completely different beast. Displacing 747cc through a bore of 67mm and a stroke of 53mm the double overhead cam motor breathes through four 34mm Keihin CV carbs and made a claimed 91 hp at 9500rpm and 51flb of torque at 8500 revs.
If all that pretty familiar, things now start getting a little unusual. For a start, the oil is carried in the frame, thereby enabling the motor to be carried lower in the frame than would normally be the case. Then there’s the altenator – carried behind the cylinders and above the gearbox in order to keep the motor slim, clutch is hydraulic, too, which helps on the low-maintenance front, as does the transistorised ignition.
In fact low maintenance is what the CBX750 is all about and to this end it came with hydraulic tappets which are self-adjusting and run at zero clearances all the time. This works by using a variable tappet filled with oil. When there’s no pressure on the rocker (and therefore on tappet) oil flows freely through the tappet body which is held against the rocker by the pressure of an internal spring. When pressure is applied to the rocker and tappet by the cam the tappets internal valve closes, thereby trapping the oil and maintaining the correct length for the required clearance. This is quite common in the car world but pretty rare in the motorcycling world (except in Harleys), which is a shame because the result is a top end you never have to look at (unless something goes badly wrong). Another interesting internal bit is the sprag clutch that prevents you locking the back wheel when knocking it down a couple of gears with 10,000rpm on the clock (something you do all the time, admit it) there’s also a rev limiter that comes in at 10,800rpm to prevent you bending valves with those missed changes (although the six-speed gearbox is a pretty sweet affair).
All this high-techery is carried in a semi-duplex cradle frame made from tubular steel and suspended by a pair of 39mm forks at the front and Honda’s Pro-Link monoshock system at the back. The forks have a fork brace as standard and are air-adjustable with three-way rebound damping – they also feature Honda’s TRAC anti-dive system which has four settings (at the bottom of the fork legs). The rear shock also has air-adjustable preload (via a valve under the sidepanel) and the rebound damping is three-way adjustable via a remote knob.
The wheels, as was the trend back in the early ’80s, are 16-inchers wearing a 110/90 at the front and a 130/80 at the back. Combined with a very racy steering geometry (27 degrees of rake and 93mm of trail) the 16-inch wheels make the CBX a very quick steerer. Yet another high-tech feature (for those days) were disc brakes all round gripped by twin-piston calipers – something very few bikes had back in 1983.
Like much of the rest of the CBX, its styling broke new ground with its twin-headlamp half-fairing and swoopy lines. The only really naff bit was the plastic pretend bellmouths stuck on the back of the carbs. These are purely decorative and detract from what would otherwise be a pretty tasty looking piece of kit.
Even seven years on from its launch the CBX doesn’t feel as dated as some bikes of that age, and swinging a leg over it gives you the impression of something nearer the 90’s than the ’70s. The first thing you’ll notice as you swing your leg over it is how high it is. Despite the engine being relatively low in the frame the seat height is a towering 31” and you feel every one of those inches – it’s a very tall, thin motorcycle. Fortunately the CBX weighs a lowly 4801b (dry) which means that those with shorter inside leg measurements than normal don’t find the bike too intimidating. The Honda starts easily and warms up quickly. Once in motion the CBX goes like a good ‘un with plenty of power on tap from 6000pm up to 9500. Below 6000 revs the CBX is a bit flat and there’s a bit of a flat-spot between 5000 and 8000rpm. The wonderfully wide and smooth spread of torque goes some way to redressing this lack of low-down power, but performance low down in the rev range isn’t sparkling. Once in the tacho needle swings past the six grand mark the CBX stonks along pretty quickly and is quite capable of keeping up with GPZ and GSX 750s. When it was first tested it turned in top speeds of 130mph and 12.3 second standing-quarters.
In the handling department capable rather than outstanding. In standard set up the CBX is soft and squidgy, feeling more like a sports-tourer than an outright sportsbike. Fortunately there’s enough adjustment available to tune the suspension to your requirements, the only thing not appearing to have any effect being the TRAC anti-dive. Even on the hardest settings the CBX still lacks that sporting edge, but even so you can hustle it along twisty back roads with surprising speed. The relatively light weight helps this, and the combination of quick steering geometry and 16-inch wheels means it is very flickable. Now that we’ve all become used to 17-inch front wheels the CBX does feel a might twitchy on fast sweepers, but generally the 16-inch wheel effect isn’t as noticeable as on something like a GSX.
Riding the CBX is a rather weird experience because the combination of a very high seat, a very narrow profile and wide handlebars makes it feel not unlike a big trailbike. It’s actually a very comfortable bike to ride because the riding position is upright (but protected by the surprisingly efficient fairing), the engine is smooth and almost vibration-free, the seat is soft and roomy and there’s even a sensible pillion perch with a grabrail. In fact the overall feel of the CBX is more of a sports-tourer than anything else and it is quite capable of taking two people and luggage on holiday without complaint.
As a riders’ bike the CBX is excellent. Apart from the good riding position and comfortable seat, the handlebar-mounted mirrors are very effective, the switchgear is the usual good Honda stuff and the instruments are surprisingly comprehensive. Apart from the usual two clocks and idiot lights there’s also a third clock that houses a surprisingly accurate fuel gauge and a voltmeter. The hydraulic clutch is nice and light (if not very precise) and the gearbox is smooth, which all makes it a nice bike to ride in town as well as on the open road.
All this sounds just a little too good to be true, fret not because nothing is perfect. Fortunately the CBX has proved to be a very reliable bike and few serious gremlins have made themselves apparent. The low-maintenance engine is pretty much bullet proof and long as it has been treated right -and that means regular and frequent oil changes. Those hydraulic tappets work very well as long as the oil flowing through them is clean, but infrequent oil changes mean that they can get filled up with gunge and stick -bad news. It’s worth the extra effort to change the oil every 2000 miles just to be on the safe side.
Elsewhere inside the engine things are pretty good. Bikes that have been used round town a lot have been known to break starter chains and some early ones wore out valve guides so watch for smoking and high oil consumption. Unlike many Hondas of that vintage the cam chain and chain tensioner have stood the test of time very well and aren’t prone to the problems that afflicted the CBX55Os and others of that ilk. The camchain should be good for around 30,000 mile, but if a new one is needed Galea Camchains will do you one for around �105 including parts, labour and VAT (phone 01-885 5861). The electrics on the CBX give very few problems, likewise cycle parts which generally are of good quality. The softness of the suspension is likely to have become worse over the years, so stiffening the front end with some heavier-weight fork oil could be a good idea. There’s not much you can do about the rear shock other than replace it with a new Honda or after-market shock. One thing to watch for are the brakes. Several years of neglect will guarantee the pistons seizing inside the caliper and rendering the otherwise excellent braking system all but inoperative. It’s worth stripping and cleaning them twice a year to prevent nastiness.
Running costs for a CBX are actually pretty cheap because apart from changing the oil regularly there’s not that much else to do. Because the CBX doesn’t put out an enormous amount of power the tyres should be good for around 5000 miles, and if the chain is looked after properly it should last getting on for 8000 miles. And that’s about all there is to be done – yep, this is really low maintenance. So how much should you expect to pay for this no-maintenance techno-miracle? Well, a high-mileage early one shouldn’t cost you much more than �1200 while a low-mileage late one (C-reg 1985) will cost around �2000.
When we tested the CBX750 back in 1985 we wondered where the CBX went wrong – on paper the CBX looks the absolute business but it somehow lacked box-office appeal. Five years on the CBX has regained appeal as a cheap, economical and reliable sports-tourer. For under two grand you can get yourself a good 750cc all-rounder that will do duty as a sports-tourer, commuter and weekend scratcher. It will also cost you very little in maintenance and running costs and reward you with cheap reliable transport. As a new bike the CBX never really caught on, but as a secondhand all-rounder it suddenly looks very attractive.
There are a couple of very obvious typographic errors in this article – the RC17 has an 18” rear wheel, not a 16”, and the oil capacity (as shown in image 3) is 3.8 litres, not 2.8.