There are still loads of old GS Suzuki fours roaring around our roads. The oldest, the GS550's and GS750's, have been around for twenty years (making for cheap insurance, by the way). The most recent, the (1989) GS850GT, surviving on the back of its shaft drive making it perfect for touring (at least to some misguided souls) and therefore in no urgent need of an update to more modern technology. The highlights of the range were the modernistic Katana 550 and 650, plus of course the GS1000, which could be tuned fairly easily to produce an excess of kicks.
Making the used scene even more interesting, the hordes of grey imports from the States. Though low in mileage, therefore likely to have years of engine life left, their suspension, steering geometry and laid back riding positions make them suitable only for moderate riding unless an expensive upgrade's contemplated. Much more of a pose than a serious mount but nevertheless worth a look on the back of their reasonable prices.
Any bike up to twenty years old is going to have some potential horrors. The GS engines are at least well built (when kept in stock tune) and only moderately powered for their capacities. There are some real rats that still have serious motive power, a rather dangerous combination but they do come cheap (£400 to £600) and as long as the frame hasn't rusted through can be upgraded via a raid on the breakers - modern suspension and wheels can actually lose mass and improve handling.
All the GS's are heavy old things, particularly the shaft drive versions which really add insult to injury. But it's possible to replace the heavyweight cycle parts with lighter stuff, get the mass down to more modern standards, knocking say 50 pounds off the overall weight doing wonders for steering and adding a bit of go to the acceleration. If that's done go up one tooth on the gearbox sprocket for taller gearing, which gives a much more relaxed feel and better fuel economy.
It's a good idea to do that anyway because even the 550 eats chains and sprockets at a very rapid rate - less than 5000 miles from the cheaper stuff. Amusingly, the engine sprocket can fall off! Equally nasty are the front discs, which ruin the pads in 5000 to 6000 miles and can turn very finicky indeed during the winter. So much so, that spares are expensive and rare in breakers. On the old stuff, three monthly strip-downs and clean-ups are the order of the day.
That front brake, especially on the 550, when used even gently in slow speed corners can cause the front wheel to rear up to the vertical with astonishing rapidly. Watch out for that on the test ride, and also check for any signs of crash damage. The Katana's, in particular, seem to have gone down the road a lot, usually writing off their front ends - it pays to know what the original wheel, forks, guard and clocks actually look like because about half of them are sporting non-standard stuff.
The duplex tubular steel frame itself's an hefty affair that rarely bends in accidents and can usually be straightened out without weakening its basic structure. It's brilliant on the GS550, useful on the 650 (which is really limited by naff suspension), merely adequate on the 750 and a touch dangerous when coping with either the 850's or 1000's mass and power. Beware, also, of old and high mileage cast alloy wheels which are starting to develop hairline cracks!
Almost any bike that's still running now should at the very least have aftermarket shocks and uprated fork springs. Alloy swinging arms with needle roller bearings and taper rollers in the steering head do make a hell of a difference to steering precision on the 750 and 1000. Whole front end's off later bikes have been used to excellent effect on both, though the GS850GT's usually left stock to idle away its life in mild touring or heavy commuting mode. The latter not a terrible buy if you don't want to ride fast, as many lived a stately life and are in good nick.
Apart, perhaps, from the electrics, which afflict the whole GS range (and the GSX models, for that matter). Most bikes by now sporting a rewound alternator, non-standard (often Superdream) rectifier and, on the older stuff, a complete rewire. It's not a good idea to let the electrical demise go too far as eventually the high voltage surges will take out the electronic ignition module!
Many ended up run with the alternator and rectifier disconnected, the battery charged overnight (good for about 100 to 150 miles if the lights and alternator weren't used). This, at least, won't do any damage to the rest of the electrical system but should be checked when considering purchase. Other signs of a blown electrical system are exploding fuses (check for heavy-duty fuses or even nails in the fuse-box), engine stuttering when the lights are switched on and bodged wiring around the battery or rectifier - sometimes just one of the alternator's coils has burnt out and the others are wired permanently on (instead of coming in when the lights are switched on).
Electrical hassles are a good bargaining point because a rewound alternator, rectifier/regulator and bit of rewiring won't set you back much more than sixty quid if you know what you're doing. If you don't, though, the electrical mess with have you pulling your hair out in sheer, total frustration.
One of the amazing things about the GS range is that engine maintenance is almost optional! The GS550 will run on regardless for tens of thousands of miles even if oil changes are neglected; only grinding to a halt when the sump's actually devoid of any lubricant. The larger bikes are a touch more finicky but give any of them a 1000 mile oil change and you can get away with murder.
This does mean that there are some neglected dogs out there. Checks for a good engine include a smooth gearchange (not to be confused with looseness caused by Katana or non-standard rear-set gear linkage wear), a lack of rattles (the clutch tinkling should disappear when the engine's revved), smoothness on the 550 and 650 (the bigger bikes vibrating a bit in the higher rev range in the bars or pegs), easy starting, smooth carburation and the usual lack of knocks, oil leaks and smoke out of the exhaust. It's also worth dismembering the engine breather to check for fumes.
Heavily tuned and thrashed 750's and 1000's can do in their crankshafts but this is rare - run away from anything that's got its engine bolts wired in, as it's been raced some time in the past. The bigger bikes will also ruin their clutches when subjected to wheelie silliness (and just about everything else when the rider loses it, these bikes don't like those kind of silly games). Valve and even camshaft demise's possible after 40,000 miles on the larger models but not something to get paranoid over.
Undoubtedly, the 550's are the toughest of the bunch, if not of all Jap fours. The Katana looks the neatest but many will be swayed by the more comfortable and classic stock model. The GS650, alone amongst this bunch, has a bit of reputation for top end frailty and isn't helped by its shaft drive and hefty mass...the 650 Katana has a useful bit of extra power over the GT but most have now been thrashed into the ground.
Well sorted GS750's, running modded suspension but stock motors (apart from the exhaust which, as in all GS models, is quick decay) perhaps offer the best compromise between power, handling and reliability. The shaft drive GS850GT's a worthy old battle-horse but a touch dangerous when ridden hard and also expensive on fuel, tyres and pads when taken long distance touring.
The GS1000S and GS1000E have tough motors but are really limited by the way the mass and power interact with the frame, even on much modded suspension. They can be ridden very fast but it needs a lot of skill and bravery to survive such excursions. Quite a few were used for moderate riding and they do offer good value. The GS1000GT was a bit of a horror show due to its excessive mass and shaft drive, avoid unless you only want a mild tourer when one of the smaller bikes would probably be better.
The best GS's turn up on the private market - all kinds of tarted up, dangerous dross in dealers, these days. Finding a good one usually takes a month or two, with lots of false calls. Demand for the decent stuff is high, with prices in the £1500 to £2000 range but a grand will buy something with a decent motor and chassis that can be cheaply upgraded. Sadly, they don't make them like this any more.
Dick Lewis