Suzuki 650 Katana

Four-pot Japanese classics are over-complicated, tricky to maintain and expensive to run, right? Not quite. Steve Bergman has clocked up over 120,000 miles on the cut-rate Katana and reckons it has real classic cred…

The Suzuki GS650 Katana has been in the ‘cheap transport’ league for a while, but now — following the fashion of the higher-capacity Katanas — these bikes are starting to become collectible. Even so, good examples can be picked up for £1500; high mileage or examples in poor cosmetic state come for loads less. Yet here is a classic Japanese bike that will do high mileage and offer ready to use, fast, efficient transport. And it’ll do all that with easy and cheap maintenance.

The GS range of Suzukis, including the Katana, is not without its faults. The most common of these is well known: trouble with the charging system. This particular problem stems from the generator or voltage control boxes. But this is more rare than some would have us believe and is easy and cheap to fix. The expensive one-piece regulator and rectifier can be replaced from the breakers with items from other bikes or new items from car accessory dealers, and the generator can be rewound for less than £50.

You may also find that bikes with over 50,000 miles on the clock tend to use a bit of oil. This is usually down to gummed-up piston rings and — given that the across-the-frame four cylinder engine is a doddle to work on — is easy to fix. Use after-market gaskets for complete economy. The even easier option is to remove the filter from the breather on the cylinder head and ride a bit slower!

The downside out of the way, with a 650 Kat you end up with a Jap classic that will be relatively maintenance free. Britbike riders might be alarmed by the idea of a ‘complicated’ four-cylinder bike. But it’s really very straightforward. The ignition is electronic; just leave it alone. The valve clearances are bucket and shim and seem never to want doing, but if they do then the shim is located above the bucket and it is a simple job to ease the bucket down and remove the shim using the wife’s eyebrow tweezers.

The camchain tensioner is fully automatic and mostly works well. The bolts, etc, on the tensioner are to hold the tensioner back on stripping the engine down but can just as easily be used to clamp the tensioner out if the spring is old and slack. The carbs always stay within reasonable balance — which is just as well as removing the screws to fit the air hoses for vacuum gauges will result in burnt fingers (we all do our carb balancing with the engine hot, don’t we?) and the air cleaner is the ‘wash, oil and go’ type.

On a cold wet winter day the last thing you want to do upon returning home from a club run is oil and adjust the drive chain. The 650 Katana has shaft drive. You wouldn’t notice it at any other time as the Kat does not suffer any of the ill effects on handling that some shaft-drive bikes do. If you were to ride the bike without looking at the back wheel first then you wouldn’t realise it had shaft drive at all.

With high mileage models you may find that the back wheel is a little bit oil-sprayed from the bevel box. Don’t worry; it is highly unlikely to be the oil seal. If cheap oil has been used in the bevel box then it may froth up and come out of the breather. Alternatively the breather may have become blocked, forcing oil past the seal. Both quick, cheap and easy to fix.

The Katana is blessed with a five gallon fuel tank, one gallon of which is reserve. With an average fuel consumption in excess of 50mpg that gives a range of 200 miles before reserve and a further 50 miles before Mr Pushit appears. Fuel consumption doesn’t vary greatly. You can expect it to drop to a low of 40mpg if you’re pushing three figure numbers on the speedo (on the continent of course, Officer!) and highs of 60mpg are easily achievable with a cool and chilled out riding style. An average speed of 80mph on dual carriageway and 70 on A-roads should give you that 50mpg average. Not bad for a bike which was first imported to the UK over 20 years ago!

The Katana is supposed to run on unleaded fuel. However if the bike has done high mileage you may find that it will suffer some problems. Using unleaded and some makes of four star will induce pinking. The correct answer is to take the cylinder head off and clean things up. However, I fitted a Fuel Cat fuel octane booster and the bike will now run on almost anything beginning with ‘pet’ and available at extortionately-taxed figures at your local petrol station.

All that would be academic on a bike if it sent your nether regions to sleep straight away — which is one of the surprising things about the Katana. Although it appears to have a sporting riding position, because of the low seat height it is surprisingly comfortable, and you will find that 200 miles non-stop is really no effort. And, of course, it will happily accomplish 200 miles in one go!

The handling of the Kat is surprisingly good. The standard twin back shocks are adjustable for spring pre-load and damping, work well and seem to last well. Both of my Katanas reached 60,000 with the original shocks. However once they are shot you need to be careful with the replacements. The standard shocks are quite long. Fitting shorter shocks will squat down the back end and splay out the front end — and you will find yourself doing impersonations of a chop, complete with associated handling! If you’re stuck then you can get away with dropping the front forks in the yokes, but even given the very good ground clearance you may need to be careful. Front suspension is adjustable for pre-load achieved by turning the adjustable thingy under the rubber grommet thingies on top of the forks. Use only the hard setting if you have the back end on hard too. Better tuning of the front end can be achieved by mixing and matching the damping oil. The standard 50% fork oil to 50% engine oil is usually OK but those of you with hard rear ends (you, not the bike) who like their rear ends hard (the bike not you) may wish to experiment.

The combination of taper roller steering head and swinging arm bearings, and a very rigid frame that outperforms the engine, means that you end up with a bike that you can have a lot of fun on without getting into trouble. Like most Jap bikes the head bearings are not very well protected from the elements, but are a standard size and available from ordinary bearing factors at a most reasonable price (many zeros below the dealer OE price). The swinging arm tapers are mounted on adjustable stub axles, a doddle to get out, grease or replace — so no excuses!

Both the Katanas I have owned have been fitted with fairings. Not your barn door jobs but just enough to keep the crick away from the neck on longer journeys. The first one was a handlebar fairing from an early Yamaha YPVS; the second is a frame-mounted top half from an old twin shock GSX750. The Kat is capable of sitting on the motorway at the sort of speed which will rapidly lose your license, but only if you have neck muscles from Gladiators or a fairing!

The standard tyres are usually replaced with a 17-inch 130-section at the back and a 19-inch 100-section at the front, both of which are 90% aspect ratio. As standard the Katana had quaint inch measured 100% aspect things which are H-rated. I have found that a V-rated tyre is more suitable as the H-rated ones were overheating when pushed a bit with the bike fully loaded. The bike is not fussy about its tyre model but it is on tyre make. It does not feel happy on Metzelers, Continentals or Pirelli tyres. It’s not that they will actually lose grip; just a case of simply not feeling right.

Dunlop Arrowmax and some of the standard ranges of Avon work OK but the best results are obtained with Avon Supervenoms. These tyres so outperform the engine that you can get away with blue murder. Supervenoms also allow superb control without white lining or any other quirks. The price you pay for this performance is in wear rates which will make Britbike riders feel a little faint. With a tyre like the Supervenom you can expect 5000 miles on the back, and 7000 on the front, although seasonal use will affect wear. With other brands this can be increased to 7000 at the back and 10,000 at the front — but with any tyre the performance will drop off as the tyre reaches its half-life. With the Katana this can result in a vagueness with the steering at higher speeds.

The brakes are well up to the job, twin discs at the front and a single at the back. The twin-piston back calliper can suffer from corrosion but keeping an eye on it and correct servicing will obviate those problems. Should neglect result in a seized back calliper then any old one from the GS range of Suzukis will do, or one from the V-twin VX800. The brakes are not up today’s standards, obviously, but are capable of out-performing the tyres so stronger brakes would simply mean locking the wheels up sooner. The pad life on the bikes I have owned has been very good; 15,000 to 20,000 at the back and 10,000 to 15,000 on the front — excellent, considering how I ride! I find the engine braking useful for trimming speed rather than continually touching the brakes.

My first Katana came to me with one of those awful Alfa 4-1 exhausts. All top end performance and flat as a pancake everywhere else. And the sort of noise that gave you headache and deafness (pardon) on a long journey (I heard that). It was sorted out by grafting a Harris exhaust (off I don’t know what) onto the back end of the Alfa downpipes and collector. What a difference! Makes you wonder how it is that a manufacturer can produce a silencer that is half the size, half the weight and works better than standard, and whilst being little ‘noisier’, can sound so much better…?

My second Katana had a Motad system fitted and at first I thought there was something wrong with the bike. The performance at the top end was very sluggish. I checked out everything else and it appeared to be the exhaust system so the collector box was modified. First it was ground away during a mad thrash in Cumbria, two-up with camping gear, which wore away the metal allowing the exhaust to ‘breath better’. After modifying and repairing the collector it now sits up much higher and the exhaust works better — and sounds better. It now has a deep mellow sound where as before it sounded a bit like a wet fart!

As far as looks are concerned, like many bikes with styling which is different you will either love the Kat or loath it. If you love it then get one, give the old tart some new boots, panties and some make-up — then this classic Jap Kat will see the second half of its life and happily go round the clock.