No-one has come close to the sheer sophistication and efficiency with which the Japanese are able to churn out four cylinder motorcycles. So well developed and designed are these complex and complicated pieces of engineering that, in their more moderate forms, they are treated as mere basic machines, hence the term, Universal Japanese Motorcycle. Though, today, the race replica four rules, UJM's are still produced by most of the Japanese factories.
They have their engineering heritage firmly in the first fours, which were treated, back in the late sixties and early seventies, as miraculous pieces of engineering at a time when the British motorcycle industry refused to dump their pushrods designs in favour of OHC's and the Italians were churning out unreliable junk or expensive classics. The defining moment, engineering-wise, in the UJM was the Z1 rather than the earlier CB750, the latter burdened with such antiquities as a separate oil tank and chain (albeit hyvoid) primary drive.
The Z1's day in the sun wasn't one of ubiquity, though, its 900cc DOHC engine as renown for its power as the chassis was for its general nastiness. Nevertheless, all the elements of its engine were to appear again and again in subsequent designs. In later days, Honda were to expend much more of its time, energy and money on its watercooled designs rather than the old-world aircooled jobs. Give Honda the credit for getting there first, showing what was possible, and Kawasaki the kudos for redefining the design a few years later.
That original CB750, for all of its design deficiencies, soon gained a reputation for toughness - not difficult in an era when early Commando's were renown for wrecking their crankshafts and most Jap stroker rivals would burn out in less than 20,000 miles. They do need regular oil changes (every 500 miles as they become older) and proper maintenance sessions at 1000-1500 miles, but even neglected examples can skip through the 40,000 mile mark. 100,000 miles is possible, by then most of the engine will be comprehensively trashed and in need of a complete rebuild - unless lavished with loads of TLC, the chassis will be unspeakable.
Handling was limited both by excessive mass and weak suspension, the latter relatively easily sorted; not as evil as the Z1, partly because it wasn't as fast. Though early ones are considered classics, the last of the series - K6/7's & F1/2's both - are definitely in UJM territory, as cheap as they are useful. There are still some that have had a minimum of owners and been well looked after at around the £1000 mark, though the F's were of passing interest to the speed merchants (if laughably slow by modern standards) and had a tendency to explode when the day went bad. A compression test on their top end's a good idea.
The CB750F2 was replaced by the DOHC 750, along with a very similar 900 version - these KZ's had an excess of power (for the day), brutal handling and poor reliability - this was an era when Hondas became synonymous with naff camchain tensioners, and the rot could go a lot deeper in these fours which were far from up to the spec of their rivals. Best ignored as an UJM unless you get desperate and they turn up cheap.
The CB750/900KZ's were replaced by the CBX750, a design which blended performance, handling and reliability as well as minimal maintenance (automatic valve clearance adjustment) in a way that few near 500lb fours had managed before. It was perhaps a bit too fast and sporting to make it as an UJM but there's no denying their usefulness at £1500 for something with about 30,000 miles on the clock. Look for top end damage as the first sign of demise, usually after 50,000 miles, though I've seen bikes with twice that on the clock still going strong.
Any pretensions to speed the CBX might've possessed were lost to a deluge of race replicas, instead Honda turned the motor mild and the styling classic, used their original four's designation in a failed attempt to take the nostalgia market by storm. In the States they were marketed more successfully as a very cheap entry level bike; no such luck in the moribund UK market (at least until the 600 Bandit came along to rattle the cage). As a 75hp 750cc four it's way over-engineered (and could usefully lose three carbs and the rear disc), therefore usefully tough; two grand up buys a CB750 still in jolly good nick. Test ride well, though.
More realistically in the UJM frame was the OHC CB650, an engine design that also stretched from the Jap market 350, through our own much loved CB400F to the classical CB500 four and the useful CB550F. The 550 emerged as the best of the bunch, having that extra little bit of performance that the 400 was lacking, whilst the 650 could turn fragile if ridden really hard - many 650's managed to lead quiet lives in mature hands; the odd bargain still turns up on the private market, though dealers try to off-load the usual nasty dross.
Classic in appearance, useful in performance and easily upgraded to a good handling machine, the CB500 four would make it as a perfect UJM except that it's so old that it's become the target of wannabe collectors; which can only be considered a great waste of a fine motorcycle.
The CB400F was one of the first Japanese motorcycles to have an ergonomic riding position, it was also compact and relatively light (based as it was on CB360 chassis parts). It only rock and rolled on the back of revs but, unusually for a Honda four, was let down by quick wear piston rings. It took a while for this fact to get through to the enthusiasts who thought they were the real thing, most have now been run into the ground but rats make viable low end UJM's at less than 500 notes. At least the 350/650's had a relatively modern wet-sump design, lacked the transmission lash and anti-theft gearchange action of the original Honda CB750.
One variant on the Honda four theme worthy of note's the DOHC version of the 650. Mildly custom in appearance it had both a tougher and more powerful engine than the OHC model; quite a lot of Yank imports turn up, as well as the equally useful 700cc version. As long as you don't want to go above the ton, when the handling turns dire, they are pretty useful bits of kit at £750 to £1500.
The 650cc four was long marketed by the Japanese as the ideal compromise between power, weight and handling, though in reality they usually weighed nearly as much as the 750's. Kawasaki had a long run with their Z650 even though it lacked the inherent toughness of the mighty Z1's engine design. Though it could sometimes make it through the 100,000 mile mark it only did so on the back of religious oil changes and at the price of almost complete disintegration of its chassis, most of the metal rusting from the inside out. Other than imports, most are now a bit too far gone to be of much interest as UJM's.
The same engine design turns up in 400, 500 and 550cc variants. The Z500 had a reputation of wrecking its camchain but later parts could sort this - more or less. The Z400 didn't have a happy blend of power and weight, was usually run into the ground without much TLC but was a tough enough nut to crack.
The 550 emerged as having the best blend of power, reliability and handling, appeared in loads of different variants. Perhaps the ultimate UJM, the shaft drive GT550 was much loved by DR's and run for unlikely mileages on the minimum of maintenance (they regularly go through the 100,000 mile barrier, some have done over twice that). Most of the mods to it, over years, have concentrated on increasing the torque rather than trying to fundamentally reform the breed. Prices run from free for something that's finally died a death to around three grand for an immaculate, low miler.
The GPz550 took the motor further - one of the few bikes that could be ridden mildly and turn in good economy (60-70mpg) whilst also being able to go into killer mode. It was sold on its sporting pretensions, but was really an UJM in disguise. As useful as they are, the speed boys destroyed most of them over the past five years.
The later alternatives are the Zephyrs. These have mild UJM motors hidden in modern-retro styling. The 750 will have old Z650 owners all nostalgic but along with the 550 and 1100, the constraints of taking an old engine design into the modern world adds up to poor economy and indifferent handling. Nowhere near as dangerous as the old seventies Kawasaki fours, mind. The portly 1100 Zephyr has a heavy appetite for fuel and consumables but its motor is well developed and tough, whilst the handling limits the degree of thrashing it's likely to get; therefore, bargains at £2000 to £3000 can be picked up on the private market with a minimum of mileage. Some of the 550's and 750's have been run into the ground, their finish not the best in the world.
The GT750's similar to the 550 version, again famed for doing large mileages though not as totally indestructible as the 550 and rather heavier going for town work. The early ones are especially worthy of care when purchasing high milers. The same goes for the Z750, perhaps the best bargains being grey imports of the custom version from the States, £1000 up.
As mentioned, the Z1 wasn't really an UJM but its successors, the Z1000 and Z1100 certainly were. Not that the engine had changed to any wild degree just that the times had moved on and what had been leading edge became merely yet another Japanese four, albeit one of the toughest in the business. As with modern Triumphs, this strength was reflected in excessive build quality that meant the 550lbs of metal was always going to be hard work.
A whole list of chassis mod's - alloy swinging arm, Koni shocks, fork brace, expensive tyres, etc - helped keep the beast on the road. Used ones are thus a mixed bag of hard ridden wannabe dogs from the speed merchants to mildly toured machines that haven't come close to having their mechanical limits tested. It is possible to wreck the crankshaft under massive abuse but it's extremely rare. You usually have to bolt on a turbo-charger!
The only other Japanese engine to equal, if not better, the Z1's toughness was the GS550. Again, excessive mass was the result of such sterling build quality, so much so that its 54 horses never made much impression on forward motion! Notable was its steady handling, secure and safe if slow turning, only possibly spoilt by a nefarious set of twin discs that reacted to British winters not at all well. Quick rot also afflicted the exhaust but so mildly tuned was the engine that it would run on straight through pipes if necessary.
The GS550 was only mildly related to the 16 valve GSX400F, which had an inadequate sump, could go as far as ruining its crankshaft. A pity because its relative lack of mass meant it shifted as well as the 550. You can pick up rat 400's for as little as £300, something that's impossible for the 550, so well has its tough reputation permeated the motorcycle community.
The GS550 turned up in Katana clothes, an improvement in styling but rather less comfortable with no better performance. The GS650 Kat, however, had a neatly tuned GS650GT mill despite retaining the shaft drive and was thus rather popular with the speed boys in its day. Although 650 GT's lasted longer than Kat's, neither had the toughness of the 550, nor for that matter the 750, which started off the GS range of fours.
In its day, the GS750 was notable for its fine handling, tough motor and good performance. It was, for a while, the best 750 around. These days it only makes it as an UJM, and there are still plenty running around, most of them with sensible suspension mod's. The maniacs could explode the clutch, the signs of age found in a less than slick gearbox (always one of the GS's series better points). A couple of grand's needed to find one of the excellent examples.
Whilst the GS750 was probably the best balanced of the GS range, the GS1000 took the idea a tad too far. Whatever extra power it made was hard to use, and internal pressure on the motor could lead to a relatively early demise if basic maintenance was neglected. Given a bit of TLC, though, like the whole GS range, it could go around the clock, the major price paid in disintegrating chassis components and brakes.
The GSX series that replaced the GS's had 16 valve heads that needed a bit more attention but had a happier blend of power and mass. The earlier examples had twin shock rear ends in a desperate need of an upgrade - usually, an alloy swinging arm was added as well. Of the 550, 750 and 1100cc models, the 550 was perhaps the most useful as an UJM and decent ones, including the later, better handling, mono-track versions (if you ignore the twitchy 16 inch front end), can be bought for around the grand mark.
Amazingly, the retro looks of latest GSX750 are offered rather than the 750 Bandit available in other markets, though they are based on the same GSXR derived air/oiled cooled motors. Too new to be of interest here, but the 600 and 1200 Bandits just come within the UJM remit - if you want to stretch a point - offer reasonable handling and excellent performance. The 600 Bandit being of especial interest as mild use of the throttle returns 60 to 65mpg. The 1200's tend to be ridden by wheelie maniacs, suffer accordingly. With either model, a great deal of care's needed to ensure that the bike hasn't been ruined.
Safer if slower ground is found on the Yamaha 600 and 900 Diversions. The latter is right out of the seventies as regards its excessive mass but doesn't suffer any major mechanical traumas. The 600 only makes 60 horses, tends to be strung along flat out when the single front disc can prove lacking in power. Beware of hidden crash damage and high milers that have been clocked. Perhaps the ultimate modern UJM, the XJ600N - a naked Divvie - was on sale for as little as £3500 new by the shadow importers in 1997 and really immaculate ones can be had for three grand on the used market. Older ones, still good buys, with less than 20 thou on the clock, go for around two thousand notes.
Although they share neither design nor any components, the inspiration for the Divvie's come from the old XJ series, which ranged from Jap market 400's to the UK's much loved XJ900. The latter started off poorly, equipped with a handlebar fairing that caused some nasty speed wobbles. Though later models, with their half fairings, were excellent in their stability when new, once some wear got into the suspension - after, say, 30,000 miles - the weaves came back in all their glory. Nevertheless, many of the 900's made it around the clock without exploding or being written off, but mostly in the hands of mature riders.
Some old heap can be had for less than £500, spruced up with a raid on the breakers. With the more expensive stuff check that the suspension ain't ruined and that the calipers aren't about to die a death. Really worn examples, over 80,000 miles, can also suffer from cracked wheels as well as all the usual rot. £1500 can either buy something in lovely condition or a bike about to expire; quite a lot of dross about. The XJ750 was closely related to the 900, had some of its toughness but never sold in any great quantities in the UK.
If the XJ900 could prove heavy and unwieldy at times, the 600 version was much more compact and useful; even had more power than the modern Diversion. It wasn't in the same league as the GPz550, more or less making it as the perfect embodiment of the UJM. It had a passing popularity as a DR hack where it proved to be reasonably tough but not up to continuous neglect of oil changes. A shot gearchange easy evidence of high mileages and/or abuse. The good ones that have been well tended reflect their easy life by retaining the sheen in their finish; the hard used examples look pretty awful. Some bargains out there at £1000, but it takes a bit of effort to track them down.
Both the XJ550 and shaft driven XJ650 have reacted to old age by wearing out without much dignity - everything from ruined chassis bearings to knocking crankshafts; a veritable minefield of possible expensive problems. They do come up very cheaply and it's not impossible to shoehorn a later XJ600 engine into the unwilling chassis. Passable UJM's in their day, now more likely to be rolling deathtraps.
Whichever Japanese four you chose - and many people are addicted to certain model ranges - there's loads of good technology hidden within their engine cases. Just because they are universal doesn't mean they can't be fun, especially if a bit of effort's put in to upgrading their chassis.
Mike R. Bracley