Yamaha's aircooled four cylinder series never really attracted a fanatical following, unlike, say, Kawasaki GPz's. Seen as sensible and urbane rather than exciting and excessive. Perhaps the failure of their triple cylinder XS750 and XS850 set the scene for their later efforts with their fours. Whatever, it really wasn't until the sheer excessive excellence of the watercooled FZR600 and FZR1000, that Yamaha really set the scene in the four stroke camp, though throughout the seventies and eighties they were dominant in the stroker genre.
That's not to say that they are without their merits. If they never really excelled, they also never plummeted to the depths of mediocrity such as Honda's CB550 or their later CBX550, which became synonymous with their naff camchain designs. Early XJ900's had a reputation for shaking themselves into high speed oblivion on bumpy roads and the XJ650's motor could turn finicky if neglected but the overall reputation of the series was for tough engineering in safe if staid chassis.
Age wasn't always kind to them. Rotten wiring, disintegrating switches, including cut-out's, rotting carbs and lack of maintenance could make any of the range, though more usually the XJ550 and 650, very finicky starters. If you find an old XJ that starts easily, chances are that it's been well looked after, if not completely rewired and upgraded electrically.
A contributing factor to poor starting and odd carburation may well be the way the stock exhaust rots away rapidly. Compounded by the difficulty of matching jetting to aftermarket four into one exhausts, especially on the smaller models. This is easy enough to check out on the test run, though it's worth noting that whilst the engine may pull well in second or third, the stutters can appear in the taller gears.
Again, clogged and neglected airfilters are a similar area of concern - the usual ploy of attacking them with a screwdriver can in, say, an XJ650 lead to a large hole in the powerband from 5000 to 7000 revs. Not impossible to live with, as it gives a usually bland delivery of power a bit more urgency when it bites, but occasionally it sends the mixture so lean that pistons are holed or valves burnt around their edges. The early stages of the latter easily spotted by smoke out of the exhaust on the overrun.
That leads on to engine toughness. Basically, they can be long-lived enough to go around the clock (twice in the case of one XJ900 we've come across!) but they do need a bit more regular attention than either GS or GPz fours, though are generally tougher than Honda fours of the same era. The modern XJ600S and XJ900S haven't been around long enough to test their merits at breaking through the 100,000 mile barrier but both so far seem to reflect their more modern design, and mild state of power, by not having any obvious faults.
Neglect of maintenance, especially those all important oil changes, on the rest of the range can quickly lead to some quite nasty engine horrors. Informal destruction testing by lazy or bored UMG contributors has blown up an XJ550 in less than 25000 miles and an XJ750 in 19000 miles. It's rather more difficult to destroy the XJ900 - not because its engine's necessarily any stronger but because its handling's limited the extent to which it could be thrashed without rendering the rider an hospital case. 30,000 miles at the very minimum, more usually 50,000 miles from the later (post '87) models.
The XJ600 and XJ900 go around the clock with the greatest of ease, and almost minimal maintenance. 550's can also achieve that fate with rather a lot more tender loving care. For 650's and 750's it's the exception rather than the rule, usually both in trouble after 50,000 miles even when well cared for - though no doubt some UMG reader will write in to complain he's done a quarter of a million miles on one; in the used bike game anything is possible however improbable.
Apart from the obvious camchain demise, usually around 30,000 miles though sometimes at as much as 50,000 miles (aftermarket replacements often do less than 20,000 miles, though!) wear can strike at the heart of the engine pretty much anywhere. We've heard of an XJ900 with knocking main's at 50,000 miles; of another with knackered valvegear at 40,000 miles, and of another with a disintegrating gearbox at sixty thou. We've even heard of one that had all three maladies at 75000 miles.
The same goes for the smaller fours, with the 650 and 750 most likely to go down. Having said all this, and going all general again, it's an unlucky XJ owner who has any major engine problems before 50,000 miles and a lucky one who remains in a state of grace for more than a hundred thou.
Luckily, any engine wear in XJ's is fairly obvious, through an excess of vibration, engine smoke and rattles or knocks. Clocked examples invariably reveal their age through the gearbox being graunchy and full of false neutrals, though clutch drag is normal after 30,000 miles. Thrashed engines usually leak lots of oil and have a jerky transmission. The way things are, mature owners almost invariably look after their bikes; reflected in both a purring engine and shiny chassis...
Much more worrying than potential engine demise, chassis rot can sweep through the machine like an incurable virus through an African continent. One of the most startling things about buying an old XJ on a sunny day is to find that after leaving it out overnight in the rain the polished finery has degenerated into a rat-like heap of rust! One reason why there are so many rat XJ's is that after spending a weekend cleaning them up, a day's commute in bad weather can leave them looking all ruined again.
As well as the previously mentioned fast rotting exhausts, expect high milers to rust through their petrol tanks, corrode the rear subframes, seize their calipers, warp their discs and cover the whole bike in corrosion. Okay, the finish isn't always that bad and in the first five years and 50,000 miles most keep themselves together in reasonable fettle but when buying an old one or high miler expect the worst.
The corrosion also seems to spread rapidly, so that an aftermarket exhaust can go the same way as the original after as little as a year and even well greased bearings only last 20,000 miles or so. Beneath the corrosion it's quite likely than the engine will be okay and the frame still straight, so it can be seen as a reasonable bargaining point to get the price way down.
Generally, XJ's don't fetch serious money and they were never the kind of class act that appealed to the retro crowd. With a little bit of persistence and hustling genuine bargains can be unearthed on the private market; even dealers don't try to hype their prices to absurd levels.
The cheapest buys are early XJ550's, around the £500 mark for something with a reasonable engine but a chassis that's a bit rough around the edges. The really nice ones, with, say, 30,000 miles on the clock and useful upgrades to the chassis, fetch up to a grand, though paying that much for a bike with so many potential pitfalls down the line isn't really recommended.
XJ650's and XJ750's cost more, though really aren't worth it, given that they are more likely to have engine problems. The only exception, grey import XJ750 Seca's with relatively low miles on the clock and in generally nice nick for £1200 to £1500 - though it's surprising how quickly and expensively the chassis can go off. XJ650's with over 50,000 miles on the clock aren't a good buy, even if advertised at less than £750.
There's a large range of XJ600's, from early rats at £500 right up to nineties models at as much as two grand. £1500 on the private market should buy a jolly nice example with a low mileage engine and a chassis in excellent nick. Even low priced ratty ones can be good value, as the engine is the toughest of the XJ series, usually has loads of life left in them.
Similarly, there's a huge range of XJ900's, from £500 for nasty old rats to as much as £3500 for really excellent nearly new ones. Two grand should buy something in fine fettle with masses of life left in it.
Neither the XJ600S or XJ900S has been around long enough to make it into the lower price range but as little as two grand for the former and three grand for latter will buy a very decent example, an awful lot of modern technology for the money. Happy hunting...
Dick Lewis