Long Term CBX Test From MotoRad

We found an article from the German magazine ‘MotorRad’ about a long-term CBX test, but it was all in German (obviously!).

german test

Former list member Aaron kindly translated it for us, and you can find the results here:

Well, i finally got round to finishing the translation of that German article for you, guys. it’s not what you’d call an amazing or a particular fluent piece of translation, but it makes for interesting reading none the less.

Thanks, Aaron

In just four months the test team unwound 25000km on the CBX750F. The quick sports machine with good handling characteristics made friends through reliability and long service intervals. Only the investigations at the end of the test threw doubt on the shelf life of the air-cooled in-line-four.

Caption of big diagram on page 29 The CBX750F stood up to the endurance test without major workshop-time. At the end of the 25000km distance, the secret life of the in-line-four shocked us somewhat more: the [Combustion chambers] of all four pistons showed stark signs of wear. The pistons had to be replaced because of this and the cylinder barrel had to be rehoned. (Pic 1). A thick film of oil-black had set round the whole of the valve seat of the inlet side. (pic 2) All the parts of the 750cc shine like brand new. Only the middle selector fork shows signs of breaking, and must be changed. All 16 Valve shaft seals are worn. New sealing rings must be built in.

Italians have taste. The Honda CBX750F in black really looks stylish. And the fact that anyone can sit on this sporty motorcycle and feel at home is clearly also known in Italy, because the first long-term-test machine was stolen right on it’s maiden voyage on the 14th April last year in Riccione

The editorial staff undertook the second run three weeks later with a new CBX, this time in metallic silver paint. This machine devoured the 25000km distance in just four months between may and September – because although the air-cooled in-line-four offers nothing spectacularly new except the automatic valve adjustment, it was still counted among the best-loved test machines last season.

Much praise at the beginning “A (literal translation here!) Bomb of a Motorcycle” in his riding diary about the victor of our comparison test of the 750s. The power delivery of the 3/4 litre motor impressed above all over 8000 rides, so that just one rider, right at the margin, criticized it heavily.

The handling of the CBX became ever more praised. How lightly she let herself change direction, standing out so comfortably because of that, because fairing and handlebars first lay down a beefy impression optically.

After 7000km the seat was regarded with the first murmured curses, “at the front and the back it’s too hard and too narrow,” according to the riding-diary. Sharp criticism was earned by the too-highly-placed passenger footrests as early as the first weekend’s expedition.

Despite the lack of seating comfort, the CBX went ever further onwards into southern climes in the big test. On this long-term-test, the testers shared two experiences: one, thieves don’t appear to like the silver-metallic paint of this machine, and second, the CBX has its best handling-characteristics when she’s moving quickly.

Only one problem showed up in the test: between 40 and 80km/h the test-Honda tended towards distinct flutters of the handlebars. An unpleasant characteristic which, however, doesn’t appear to affect all CBX models. About half of the readers who noted their experiences of the new in-line-four machine for MOTORRAD (literally MOTORCYCLE, its the magazine’s name) however, did sense this trend. In any case, this flutter in this speed area is already triggered, when the rider takes one hand from the bars to open his visor.

One cause of this unnerving fault being on some machines and not others is the steering geometry of the CBX, which has been biased extremely towards handling. With a wheelbase of just 1465mm, a relatively short trail of 93mm and all this combined with a 16” front wheel, the tolerance-region of the production cycle-parts and tyres is small. One small deviation is enough, and already there’ll be problems.

In principle, all machines that are easy to stir for these reasons also react delicately to false loading. Especially strongly marked are the fluttery characteristics of the Honda, specifically, as soon as either two people or one person and his luggage must be loaded on the rear. As more weight is placed on the rear, the handlebars react proportionally less and less peacefully. Because of this, heavy luggage should, in such cases, always be carried in a tank bag. So loaded, according to the experiences of MOTORRAD riders, the CBX moves itself when riding solo without any problems.

The tires hold the strongest influence on this chassis tendency. Here the test editor sought and found a great many combinations. The Honda runs completely correctly on new tyres of the same make. After 1500km use of the rear tyre, the matching front reacted even more sensitively. The handlebars were properly stubborn, as the test machine through emergency rolled on not permissible mixed tyres: The Metzeler on the back absolutely didn’t go with the Dunlop on the front. Only a little improvement was gained through putting a new Michelin on the back.

(Caption of diagram on page 32) A motor with such a compression-diagram (below) can’t run much further. In fact, the [water pestle] for the valve measuring device just wasn’t playing along with the measuring.

Because of this, tyres from different manufacturers should never be mixed on the CBX750F. Tyre variations are permitted by the Jap-Bike richly: Honda gives tyres free from Continental, Michelin, Metzler and Pirelli. The OEM tyre fitting from Dunlop, according to MOTORRAD experiences, is the best harmonisation for the sensitive cycle-parts.

However, as much as handlebar flutters and tyre choice were cursed during the test kilometres, the machine didn’t get any other complaints. Four days the machine stood in the workshop – but that only because there was no new O-ring chain available. With style and élan cycle-parts and engine stood up to the long-term test (inset diagonally) through south Europe just as reliably as city traffic and full-throttle sprints.

Only one single time did the 4-cylinderer have to go into a workshop. MOTORRAD Editor Juergen Wellisch, with his wife and the Honda on a weekend-trip, all the fork oil ran in Friedrichshafen because of a defective gasket ring in the anti-dive-system. This couldn’t spoil the fun of the CBX for Wellisch: “Apart form this it’s problem-free and very good handling,” he noted fairly in his riding-diary.

Conspicuously added to the Honda-Logbook only the high oil usage of the unit. On its back-and-forth through half of Europe, the machine used 13litres of oil between inspections, in ever-greedier gulps. As soon as the oil level of the CBX fell just a little under maximum, the automatic valve adjuster made clear noises. The same happened when the motor was demanded heavily of when it was hot outside. Then the oil detracted from the function of the [water pestle].

On this motor, the rider should never use the full tolerance of the dipstick: “always fill right up to the maximum and keep a regular eye on it” is also what Honda-Germany recommend.

One litre of oil in every 1000km is added by the Honda-Works-Technicians to their air-cooled CBX750F motor. But about double that was needed by the test-machine in the last 1500km of the test. Reckoned over the last 10000km of the test, the engine needed an average of 0.9litres per 1000km.

(Caption of picture on page 36) Whether in sunny South France or Swiss alpine passes: The 4-cylinder accounted well for itself on the long-term-test.

In opposition to this, the in-line-four was fundamentally more comfortable in its use of gas. In the best value case, the 91BHP machine sucked 5.5 litres of super-unleaded through the four Keihin carbs in 100km, but during extreme Autobahn (that’s the German motorway which has absolutely no speed limit) hunting, it went up to 11 litres. (That’s 51mpg and 26mpg) With an average of 7.2 Litres per 100km (that’s 39mpg) the CBX is in the accepted margins. From the readers’ letters, we’ve collected a very similar average and a range from 4.6 to 12 Litres per 100km. (that’s 61mpg and 23mpg- aren’t I good to you?)

As with gas consumption, the Honda also has a talent for uneven wear in parts a way otherwise only reserved for a Scotsman’s. At km 20550 (12,769 mi) the CBX needed new brake pads at the front, 300km later the chain and sprockets, just like the bushing on the swinging arm. Almost exactly 5000km (3100 mi) was the life span of the rear tyre on the test Honda. The front was ripe for a change at about 13000km (8000 mi).

Broken indicator mounts count amongst the teething troubles of the new model. As with many readers’ bikes, the test machine also lost both mountings. MOTORRAD is satisfied to let the guarantee sweat the mount, instead of renewing the complete bottom section of the fairing. In the mean time, say Honda, the material weakness of the part has been strengthened – on the test-machine anyway, there were otherwise no problems.

At the end of test measuring, the Honda sprinted through the lights at 200km/h. The editorial staff was utterly surprised at the compression diagram taken at the closing-test because of this. The middle cylinder had to just be a blip they reckoned, and the motor could have only chugged along with half of its power.

Astonished from this result, which didn’t change even after many repeat measurements, MOTORRAD technician Siegfried Guettner went Stressed at the dismantling of the motor. A damage that he could be responsible for was what he didn’t want to make. Some light was only brought to the darkness with a phone call to Honda in Offenbach.

There, tests with the CBX750F were run through already, that had shown such “exceptions” in singular cylinders. Importantly, it wasn’t always the case, like in the case of our test machine, that it was the middle two cylinders. Honda hold firmly, that the [water pestle] for the automatic valve setting could show up lack of functioning at the compression measuring, as long as the motor still wasn’t at the operating temperature of 80 degrees C. At lower temperatures, these tests could see the valves sometimes staying open, so giving results like on our test-machine.

That this effect doesn’t show up in normal conditions shows, according to the factory, that there is no resulting damage to be expected. Despite this, the Franchise in Offenbach has requested Tokyo to investigate this phenomenon further.

Also at MOTORRAD, the investigations into the air-cooled 4-cylinderer continued. The dismantlement of the cylinder head had already figured itself as elaborate and involved, because innumerable screws for oil passages and stubborn mules had to be undone. Right up to a Remover for the alternator no special tools are demanded for the dismantling.

The secret life of the 3/4-litre machine gives the following picture: all four cylinder bores show very light scratched. On all of the piston crowns hard oil-carbon-crusts have built up against these, the damage affected: The combustion chamber, that is, the area above the uppermost piston ring, show strong scratches, which are covered with gradually crumbled deposits. On the shafts, although the quartet of pistons left no lack, there are no traces of running here. Due to the damage to the combustion chambers, the pistons need to be replaced anyway, and the cylinder liners honed.

Like on the pistons, the valve faces of the inlet side a have heavy oil-carbon-film. The reason: All of the [Valve shaft oil wipers] were missing so much tension, that an exchange is unavoidable. Through this, the heavy oil consumption of the test machine can be explained. The condition of the Valves gives, despite this, no reason to complain. At the rebuild they’ll just have to be newly seated, since there are light traces of corrosion visible on the seats.

Pleasantly unproblematic proved the rest of the CBX motor; Gears and locators were in the best of conditions. Only the middle selector fork, which was engaged in third gear and should checked out between fourth and fifth gear, showed an approximately 0.3mm deep trace of wear and should be replaced.

The Starter and [Gleitlagerbestueckung] presented themselves without visible and measurable wear. The coupling with the Anti-Hopping-System stood up to the 25000km well, even the Chassis, it’s bearings on the steering head, swinging arm and the Pro-Link links showed no unevenness.

(Caption page 39) In fast curves the CBX remains easily flickable

Reckoned all in all, the maintenance costs of the CBX motor at the end of the test sit at 1735 Marks. (No idea what West German money was worth in 1985!) While its deployment suffices the sporty racer, in opposition to that the average cost per kilometre is 25.3 Pfennigs. The competition from its own stable, the VF750F, lay something like 0.5 Pfennigs higher in it’s long-term-test. The Kawasaki GPZ750 and the XJ900 from Yamaha are both 2 Pfennigs per Kilometre cheaper to run. Doubtless, the CBX has many strengths, however in consideration of the advisable repair work at the end, a painful memory of the first CB750 is awoken. From the image, Honda still profit today. In reliability the in-line-four of the 70s enjoyed a similar reputation as the Beetle did amongst cars.

As a modern variant of this earlier 750-bike, the CBX750F is a good compromise born out of proven, practical and time-honoured technology. However, in view of the tribute of about 1700 Marks already paid to it after 25000km, there remains a little portion of deception.

In opposition to the CBX unit, the valves of the old four-cylinder-engine had to be seated every 6000km, but due to this it could go on for 100,000km without sustaining any damage worth naming. Short-livedness should not be the sacrifice which, according to modern claims, has to be paid to enjoy riding.

Reader experiences of the Honda CBX750F (page 37) In the main, all 38 readers’ letters that MOTORRAD have received about the long-term-test of the CBX750F speak of contentedness. In any case, 28 of the readers have written that they would straight away buy the CBX again. Praise and points of criticism in these 38 letters agree overall with the experience of the MOTORRAD editorial staff. Because the readers had between 3000 and 16000km (2,000 and 10,000 mi) under their belts, we have a pretty good representative result.

The gravest problem sensed by readers, as by the members of the editorial staff, is the handlebar flutter of the Honda between 40 and 80km/h. Half of all writers classify this as at least distracting, but most as even dangerous. 30% of the riders and passengers cited the limited suitability of the CBX for use with a partner. One fifth have – like the editorial staff – problems with breaking indicator mounts. Large praise is given by all to the handling, service and speed of this machine.

Letters I am restlessly enthusiastic about the machine. The Honda is only a bumpy ride on the day with worn right out tyres. If I should reach a high kilometerage on this motorcycle by the end of the production run, I would buy another one of them.” Wolgang Kurt

“The disappointments, which I could discover up until now, limit themselves to the enduring flopping back of the left mirror, and the stability of the front indicator mounts, which were both broken off by 6000km.” Hans-Georg Kleinschmidt

“First class straight line running when riding solo, somewhat weaker with a pillion. The Pillion seating is miserable for a normal sized passenger.” Hans-Christoph Mohr

“Excited by the ride quality. Workmanship dubious. Exhaust collector box rusty after a short time. Consumable items very expensive. I’d buy it again in a flash.” Thomas Bachner

“Under 6000rpm not much goes on, but above that it shifts! Biggest plus point is the long service interval. Disappointment: miserable workmanship.” Alfred Kordwig

“Four months after the new creation, the same motorcycle is 938 Marks cheaper. What can one say to that?” W. Gagg

“Singular defect: The oil passage to the left [oil cooler] is burst in the bend. Fixed under guarantee, but a 14 day wait for replacement parts.” Heinz Werner Geiger

“Caution is required, when the oil level – especially in summer – is even a little bit under maximum. At higher revs the hydraulic adjuster apparently don’t get any oil any more, and then the valves chatter.” Leonhard Kessler

“In my opinion the CBX750F is the best contemporary match of sportiness, everyday usability, looks, technology and price.” Walter Lengauer

“All in all outstandingly good machine with the best road holding and a strong motor.” MD Manfred Rath

“When I let the left handlebar go to open my visor at about 60km/h, the handlebars started to wobble, so that we nearly crashed. Should the exchange to needle roller bearings have no success against it, then this will definitely be my last Honda.” Hans Juller

“Apart from rattling noises in the exhaust area, a defective o-ring in the forks and screws on the screen that vibrated out, at 10,800km I have no problems. The machine excites me.” Michael Kauss

“I’ve been waiting 6 weeks for a new exhaust. But I’d buy one again straight away.” Bernd Schaller

“We do the first few KM with mixed feelings – we have known cases where the two middle pistons give up.” Werner Roos

“Because I’ve felt very let down by this highly praised bike since the beginning, I’m going to sell it as soon as spring gets here. Someone else can struggle with it. I often go between two gears into nothingness; the coupling often doesn’t grip properly. By around 20000km a worrying fluttering of the handlebars became noticeable, that didn’t go away even with new tyres – my workshop cautiously built large main jets in the carbs and opened up the other jets heavily. The reason: They’ve already had 3 CBX750Fs with seized motors in there.” Werner Kupferschmid

Honda on the criticism of the CBX750F (page 39) Honda on the handlebar flutters between 40 and 80km/h Every cycle-parts is a compromise between stability and handling. Good handling requires a short trail – in the case of the CBX750F it’s 93mm – which is through and through a cause of the so-called shimmy-effect. This construction requires the series condition of the vehicle; light bar-shakes are controllable every time and totally dangerless. We know however from giving away various tyres, that the use of any other than the same series of tyres will make this fluttering noticeable, despite this it remains controllable.

Honda on the loud valves Fundamentally, it remains our conviction that occasionally audible noises from the area of the cylinder head are caused by the hydraulic valve adjusters. These noises only step up in the following situations, and only for a short time in idle:

  1. After long, fast Autobahn usage
  2. with too low an oil level
  3. with poor oil quality. The noises detract in no way from the lifespan or speed capability of the unit.

Honda on traces of wear in the middle cylinders Before every journey’s beginning one should check the oil level, and this is especially the case with the CBX750F. The cases of damage that have become known to us are caused through lack of lubrication, the result of too little oil.

Honda on breaking Oil passages In chassis of the product we noticed that because of vibrations of the Oil raising pipe in the region of the shift lever could become unsealed. For the affected vehicles, we are preparing a solution. Dealers and customers will be informed of this shortly. From frame number RC 17 200 3407 on, the oil-raising pipe will be changed from the factory.

Honda on the indicator mounts Relating to this complaint: problems will be dealt with under the framework of the guarantee through our contract-dealers. From the model year 1985 the indicator mounts are being strengthened at the factory.

Honda on loose silencers >From frame number RC17 200 8257 on, the exhaust mounts will be changed, which should solve the silencer problem. As far as reasons to the complaint, this will be regulated through our contract-handlers in the framework of the guarantee.

Honda on getting replacement parts Necessitated through the removal in the new central parts depot not excluding delays. We ask after the time for understanding. In the mean time, the usual good parts supply has been put back in place.

By Claudia Schneider, in MOTORRAD magazine April 1985. Translated by Aaron Mortimer (a_morti@hotmail.com) April-July(!) 2004.