For most of the sixties the British factories dominated the motorcycle scene with a series of 500 and 650cc twins. Light, fast and economical, eventually their lack of development, excess of vibration and dubious reliability allowed the Japanese to take over as the main producers of motorcycles. Honda started the ball rolling with a series of OHC engines that had far superior engineering, as well as more power per cc. Most other Japanese companies used these strong, if basic, twin cylinder designs as the inspiration for their own later efforts.
In the seventies and eighties, Honda mostly neglected the genre in favour of their four cylinder bikes. Only belatedly catching up with their rivals when the water-cooled CB500 made an appearance in 1994. Even then its top end performance wasn’t up to the market leader, the GPz500S - a bike which basically messed up by failing to develop its power to weight ratio, or keep its price at a competitive level.
Amazingly, in the middleweight vertical twin game, only the CB and GPz offer any real signs of development, though compared with the way the four cylinder bikes have evolved, they are both pretty abysmal. Of course, Yamaha have managed to retain their hold on the big twin market, having started with the XS650 in the early seventies and eventually emerging with that most powerful of twins, the TDM85S0. This is a bit of a mess engineering-wise with a silly separate oil tank and an excess of balancers, but nevertheless manages to knock out an incredible amount of torque and be reasonably smooth.
Suzuki, meanwhile, climaxed early in the game, not doing much to the development of the breed since the GS400 emerged in the late seventies. For sure, the GS500E and GS450 aren’t bad bikes but they just aren’t up to the standards of the other machines.
Suzuki also made a 650 twin, the Tempter, which is cheaply available on the grey import circuit and not bad value if you don’t object to the mild custom stance. Spare parts are difficult, although many Continental countries, such as Belgium, had them on offer so it’s not a total disaster. They tend to be a bit tatty around the edges but quite an interesting trip once under way, with better performance and handling than the XS650. Reasonably priced at around £1250. And, yes, they do suffer from the infamous Suzuki electrics!
Of all the modern machines, the one to most effectively merge speed, lightness, smoothness, reliability and general performance’s the Kawasaki GPz500. Its excellent aerodynamics allows it to make the most of its 60 horses - 125mph, would you believe? Acceleration ain’t quite arm wrenching, handling of the sixteen inch wheel version can be traumatic and its daft hyvoid primary chain causes some jerkiness at low revs, but if you want the same kind of usefulness that the old Brits delivered without their mechanical horrors, then this is the bolide to go for. £1500 up for the decent stuff.
Generally, it’s a tough engine, up to as much as 75000 miles. The only downside is when thrashing is combined with neglect of oil and filter changes, which can cause the cam lobes to score heavily quite hard to check without taking the cylinder head off. Poorly looked after bikes are easily sussed by the excess of surface rust on the chassis - DR bikes can look like total rats after a mere winter. Also, high milers have rough gearchange actions and the suspension goes loose after 10000 miles. Check the front disc caliper for partial seizure (it squeaks!), the silencers’ undersides for rust and look for minor signs of crash damage.
The GPz500’s engine turns up in a few other models, in detuned form, but doesn’t really work as well in either custom, trail or plain Jane format. The GPz blends the best the mill has to offer in a highly effective package - as at home in the daily commute or on a motorway tour or being thrown through the country lanes.
Where the Honda CB500 scores is in real world riding, its more civilized running and extra low rev torque making it a tad more laid back, but at the same time more precise in its handling without the GPZ’s fast floater of a front 16 inch wheel. Where the Honda loses out is above the ton, when its lack of a fairing and high rev power shows up - totally lacking the GPz’s kick at the ton in top gear.
In the seventies and eighties, Honda mostly neglected the genre in favour of their four cylinder bikes. Only belatedly catching up with their rivals when the water-cooled CB500 made an appearance in 1994. Even then its top end performance wasn’t up to the market leader, the GPz500S - a bike which basically messed up by failing to develop its power to weight ratio, or keep its price at a competitive level.
Amazingly, in the middleweight vertical twin game, only the CB and GPz offer any real signs of development, though compared with the way the four cylinder bikes have evolved, they are both pretty abysmal. Of course, Yamaha have managed to retain their hold on the big twin market, having started with the XS650 in the early seventies and eventually emerging with that most powerful of twins, the TDM85S0. This is a bit of a mess engineering-wise with a silly separate oil tank and an excess of balancers, but nevertheless manages to knock out an incredible amount of torque and be reasonably smooth.
Suzuki, meanwhile, climaxed early in the game, not doing much to the development of the breed since the GS400 emerged in the late seventies. For sure, the GS500E and GS450 aren’t bad bikes but they just aren’t up to the standards of the other machines.
Suzuki also made a 650 twin, the Tempter, which is cheaply available on the grey import circuit and not bad value if you don’t object to the mild custom stance. Spare parts are difficult, although many Continental countries, such as Belgium, had them on offer so it’s not a total disaster. They tend to be a bit tatty around the edges but quite an interesting trip once under way, with better performance and handling than the XS650. Reasonably priced at around £1250. And, yes, they do suffer from the infamous Suzuki electrics!
Of all the modern machines, the one to most effectively merge speed, lightness, smoothness, reliability and general performance’s the Kawasaki GPz500. Its excellent aerodynamics allows it to make the most of its 60 horses - 125mph, would you believe? Acceleration ain’t quite arm wrenching, handling of the sixteen inch wheel version can be traumatic and its daft hyvoid primary chain causes some jerkiness at low revs, but if you want the same kind of usefulness that the old Brits delivered without their mechanical horrors, then this is the bolide to go for. £1500 up for the decent stuff.
Generally, it’s a tough engine, up to as much as 75000 miles. The only downside is when thrashing is combined with neglect of oil and filter changes, which can cause the cam lobes to score heavily quite hard to check without taking the cylinder head off. Poorly looked after bikes are easily sussed by the excess of surface rust on the chassis - DR bikes can look like total rats after a mere winter. Also, high milers have rough gearchange actions and the suspension goes loose after 10000 miles. Check the front disc caliper for partial seizure (it squeaks!), the silencers’ undersides for rust and look for minor signs of crash damage.
The GPz500’s engine turns up in a few other models, in detuned form, but doesn’t really work as well in either custom, trail or plain Jane format. The GPz blends the best the mill has to offer in a highly effective package - as at home in the daily commute or on a motorway tour or being thrown through the country lanes.
Where the Honda CB500 scores is in real world riding, its more civilized running and extra low rev torque making it a tad more laid back, but at the same time more precise in its handling without the GPZ’s fast floater of a front 16 inch wheel. Where the Honda loses out is above the ton, when its lack of a fairing and high rev power shows up - totally lacking the GPz’s kick at the ton in top gear.
This makes it relatively easy to chose between these two models. Bear in mind, if buying a newish one, that there are discounters out there who will give 15 to 20% off the absurd retail price of new models. Even bigger discounts are available for the Suzuki GS500E and it’s possible to buy one on the used market for less than a grand which still has plenty of useful life in it.
The GS has some of flightiness of the
GPZ’s front end (it seems much looser but doesn’t flip away so
violently) and a quite hard revving engine. The only real reason to buy one, other than price, is if you don’t want the complexities of watercooling. The
basic design goes back to the GS400, and has been much copied by other
manufacturers. The 180 degree crank with a single, gear-driven, balancer
emerging as the definitive design for 500cc twins, whether they be cooled by air or water.
Reliability and finish of the GS500 is very variable, depending mostly on frequency of oil changes and some elbow grease from the owner. Neglect both of these and rat city is reached with inordinate haste. It’s a rare owner who keeps his bike well polished and avoids basic engine maintenance, so overall appearance is as good a guide as anything else. A hard ridden GS500 can be a reasonably fast if enervating buzz.
Yamaha’s unorthodox design philosophy in their TDM850, whether it be 270 or 360 degree cranks, at least adds an element of modernity via its five valves per cylinder head and radically canted forward top end, the latter helping both air flow into the combustion chamber and lowering the centre of gravity.
TDM’s often have naff gearchanges but the engines can run for at least 50000 miles with just a modicum of maintenance; some have gone around the clock without needing a strip down. Valve wear can be a problem on high milers. Some useful tuning kit available, though the easiest way to get more kicks is to fit a loud 2-1 exhaust, which also loses an awful lot of mass.
1996 models re-invented themselves with a 270 degree crank, which means there’s both a bit of torque reaction and primary vibration to quell via .the balancers, though probably less so than having the pistons moving up and down together - it doesn’t compare with the set-up on the GPz500 or CB500, either in smoothness or mechanical efficiency, the TDM engine always giving a slight hint that it’s tearing itself apart.
The reasons for the 270 degree crank are that the power at the back wheel is more controllable and the exhaust sounds more like a Ducati - in theory, anyway! Yamaha even went so far as to dump the excellent Deltabox frame for a messy tubular trellis inspired by the Ducati 900SS... unfortunately the TRX8S0 just ended up looking like someone had thrown disparate components together, although their lack of popularity meant deep discounts for new ones. Some specials builders have managed to produce 350lb bikes based on the TDM engine, which is basically what Yamaha should’ve strived for; there’s an awful lot of junk that can be dumped, not least the god-awful half fairing.
TDM prices go down to £2500 for reasonable if old bikes. It’s also possible to buy a cheap XTZ750, dump all the ridiculous trail gear and emerge with a cheap and cheerful road bike that has a strong and gutsy engine at its heart. There’s a marvellous piece of engineering trying to get out of these big twins but one that needs to revert to the 180 degree crank and wet-sump design that has been so well proven elsewhere.
Any other kind of design applied to the vertical twin produces too much vibration which needs excessive balancers to counter. The 180 degree crank, with its pistons moving up and down alternatively has perfect primary vibration but a torque reaction along the length of its crank, which is easily dealt with by a single, gear-driven, balancer. Of course, the resulting exhaust note is somewhat offbeat but use of a 2-1 gives such an engine a lovely gurgle.
There are an awful lot of machines that have varied from the above concept, much to their cost. The purest vertical twin solution is the 180 degree crank without a balancer. Honda used this in the sixties, making merry with the CB450, amongst others. Both Kawasaki and Yamaha have tried the design in later models, with mixed success.
The British stuck resolutely to the 360 degree crank, essentially two singles side by side with massive consequent primary vibration. Their weak, two bearing, crankshaft would probably have exploded if subjected to the longitudinal torque reaction of the 180 degree crank design - the puny main bearings would’ve been rejected by the Japanese for use in their 250’s. The total failure of the British industry is down to their inability to deal with the vibration, which rose to alarming levels when capacities and power were increased.
There were two options favoured by the Japanese when dealing with the vibration from 360 degree crank designs. The first, as exemplified by Yamaha in their XS650, was to build in mass to absorb the buzzing. High build quality of the motor also helped, along with its low state of tune, making it one of the toughest engines in the world. However, making a vertical twin as heavy as a four and slower than an old British twin isn’t exactly a recipe for success, the engine ending up in a custom chassis of massive mass and odd handling.
The original XS-2 (there was an XS-1 but it was never officially imported into the UK) managed to combine excess mass with nasty steering geometry, especially when compared to the British twins from which it got its inspiration. Whilst the motor wasn’t the most exciting in the world, the rider was ever aware that the thing could go into a high speed wobble that would have them fighting the tarmac within moments.
Upgrading the suspension (with stuff off old British twins) helped but never entirely cured the beastliness. No problem, though, if you never break through the speed limits. Curiously, XS-2’s sell at a premium to later models; therefore best avoided.
The XS-2 was replaced by the XS650. The chassis was given a thorough going over (which added some mass) and the motor neutered. First impressions are of a nicely secure ride but given a combination of bad conditions the speed wobble comes back. People will deny this, but do 95mph on a rough road with some luggage on the back and see if you survive it. Be
Yamaha’s unorthodox design philosophy in their TDM850, whether it be 270 or 360 degree cranks, at least adds an element of modernity via its five valves per cylinder head and radically canted forward top end, the latter helping both air flow into the combustion chamber and lowering the centre of gravity.
TDM’s often have naff gearchanges but the engines can run for at least 50000 miles with just a modicum of maintenance; some have gone around the clock without needing a strip down. Valve wear can be a problem on high milers. Some useful tuning kit available, though the easiest way to get more kicks is to fit a loud 2-1 exhaust, which also loses an awful lot of mass.
1996 models re-invented themselves with a 270 degree crank, which means there’s both a bit of torque reaction and primary vibration to quell via .the balancers, though probably less so than having the pistons moving up and down together - it doesn’t compare with the set-up on the GPz500 or CB500, either in smoothness or mechanical efficiency, the TDM engine always giving a slight hint that it’s tearing itself apart.
The reasons for the 270 degree crank are that the power at the back wheel is more controllable and the exhaust sounds more like a Ducati - in theory, anyway! Yamaha even went so far as to dump the excellent Deltabox frame for a messy tubular trellis inspired by the Ducati 900SS... unfortunately the TRX8S0 just ended up looking like someone had thrown disparate components together, although their lack of popularity meant deep discounts for new ones. Some specials builders have managed to produce 350lb bikes based on the TDM engine, which is basically what Yamaha should’ve strived for; there’s an awful lot of junk that can be dumped, not least the god-awful half fairing.
TDM prices go down to £2500 for reasonable if old bikes. It’s also possible to buy a cheap XTZ750, dump all the ridiculous trail gear and emerge with a cheap and cheerful road bike that has a strong and gutsy engine at its heart. There’s a marvellous piece of engineering trying to get out of these big twins but one that needs to revert to the 180 degree crank and wet-sump design that has been so well proven elsewhere.
Any other kind of design applied to the vertical twin produces too much vibration which needs excessive balancers to counter. The 180 degree crank, with its pistons moving up and down alternatively has perfect primary vibration but a torque reaction along the length of its crank, which is easily dealt with by a single, gear-driven, balancer. Of course, the resulting exhaust note is somewhat offbeat but use of a 2-1 gives such an engine a lovely gurgle.
There are an awful lot of machines that have varied from the above concept, much to their cost. The purest vertical twin solution is the 180 degree crank without a balancer. Honda used this in the sixties, making merry with the CB450, amongst others. Both Kawasaki and Yamaha have tried the design in later models, with mixed success.
The British stuck resolutely to the 360 degree crank, essentially two singles side by side with massive consequent primary vibration. Their weak, two bearing, crankshaft would probably have exploded if subjected to the longitudinal torque reaction of the 180 degree crank design - the puny main bearings would’ve been rejected by the Japanese for use in their 250’s. The total failure of the British industry is down to their inability to deal with the vibration, which rose to alarming levels when capacities and power were increased.
There were two options favoured by the Japanese when dealing with the vibration from 360 degree crank designs. The first, as exemplified by Yamaha in their XS650, was to build in mass to absorb the buzzing. High build quality of the motor also helped, along with its low state of tune, making it one of the toughest engines in the world. However, making a vertical twin as heavy as a four and slower than an old British twin isn’t exactly a recipe for success, the engine ending up in a custom chassis of massive mass and odd handling.
The original XS-2 (there was an XS-1 but it was never officially imported into the UK) managed to combine excess mass with nasty steering geometry, especially when compared to the British twins from which it got its inspiration. Whilst the motor wasn’t the most exciting in the world, the rider was ever aware that the thing could go into a high speed wobble that would have them fighting the tarmac within moments.
Upgrading the suspension (with stuff off old British twins) helped but never entirely cured the beastliness. No problem, though, if you never break through the speed limits. Curiously, XS-2’s sell at a premium to later models; therefore best avoided.
The XS-2 was replaced by the XS650. The chassis was given a thorough going over (which added some mass) and the motor neutered. First impressions are of a nicely secure ride but given a combination of bad conditions the speed wobble comes back. People will deny this, but do 95mph on a rough road with some luggage on the back and see if you survive it. Be
The XS650 was relatively well sorted compared to its custom siblings, which really weren’t much use above 75mph. The only reason to buy one of these big twins is the engine’s toughness. An incredible bit of OHC engineering that will take wanton neglect and come back for more. Engines that rattle loudly need the valves doing but still run OK!
There’s also an 840cc kit which causes enough vibration to crack up the pavement on which the bike is perched but doesn’t necessarily cause the engine to explode — it’s that tough. Well sorted engines can liberate 65 to 70 horses, making it rather more fun than stock.
£1500 is the going rate for a decent XS650. It’s one of those bikes where there’s a huge variation in general condition that isn’t reflected in the price. Some have been clocked and have piston ring problems but generally chassis rot is more of a concern than engine viability. The nicest ones I’ve seen are grey imports in Halco’s who specialize in XS650’s, the rough ones tend to turn up in importers who are also breakers.
Rough bikes will have naff calipers, rotten exhausts, ruined suspension and marginal electrics. It really does pay to look around for the best deal rather than accept the first bike on offer. A lot run non-standard chassis parts, some of it good, some of it horrible.
The other route to curbing vibration was to fight it with two balancer shafts, usually chain driven, an excess of engineering madness that was exemplified by the Kawasaki Z750, though also blighted the Yamaha TX750, not to mention the Superdream range and Kawasaki’s Z400/440, though the latter were not so unreasonable designs as the lack of cubes meant vibration absorption never had to reach silly heights.
None of these designs are really recommended, as time tends to magnify their flaws - once a bit of wear gets into the balancers’ chains, vibration increases to British bike levels and fuel economy becomes terrible. Basically, the mass and frictional losses remove all the virtues inherent in the vertical twin design.
Having said that, both the Z440 and Z750 are useful hacks, that will plod along for 50000 miles on the back of their torque.. Never doing anything to excess but always working reliably enough to endear themselves to people who no longer view speed as their god. They are also cheap, around £500 for something useful, although really immaculate import Z440’s from the States fetch over a grand - not bad buys as long as the mileage’s genuinely low, as the motor was well sorted (unlike the Z400 which had a finicky top end and pistons in early incarnations)
Superdreams are another bag of nails. Quite literally rotting away beneath their riders once past 50000 miles, occasionally at half that mileage. Many owners have dumped the whole mess of the balancer system, finding that vibes are no worse after some wear gets into the system. This is shit engineering, that doesn’t sit well on the used market as a seemingly fine bike can go completely rotten within a week or two. It’s not sensible to pay more than a couple of hundred quid for one unless you’re sure it’s genuinely low mileage and well loved. Ride a few to get a feel for the good ones.
The CB400N is actually a marginally useful device in terms of performance, topping out at 110mph and staying on the road with reasonable fidelity. Many an owner got a perfectly decent 25000 miles of use out of them. The 250 version doesn’t develop enough power to really shift its mass and the single front disc is marginal even when not half seized up. Hack country, only buy if cheap. The custom version has little going for it save the fact that it tends to have an easier life and therefore lasts a bit longer before going into total rot mode.
The CB350S took over from the Superdream, sporting a bright red wraparound frame and a modicum of style in contrast to the older bikes. Engines ran reliably for the first 30000 miles, or so, then did the usual Superdream trick of wearing out fast. More so in this case as the majority of them were harshly thrashed, quite a few dying an early death over the DR circuit.
Chassis life was the usual mixed bag of seizing calipers (even the odd disc exploding when it wore very thin), naff chassis bearings and a general ease of corrosion that would have made the bike a laughing stock compared to fifties’ British twins. Not a bad bike to ride, by any means, but one that doesn’t age very well. About £750 for something with a bit of life left and a dull rather than rusty chassis. As little as £250 for the real rats.
Presumably because the Japanese market sensibly had no interest in such designs, Honda sourced their CB450D from the third world where quality standards are often doubtful. For a nineties’ machine the bike had little going for it other than an adequate turn of speed. Build quality was at best questionable but usually OK for the first couple of years; absolutely no reason to pay more than a grand for even a low miler.
Contrast the cheap and nasty design of the Superdream with Honda’s earlier efforts in the sixties. A whole host of vertical twins, from 125 to 450cc. The CB450 being by far the most useful, having over 40 horses; loads of blood and guts. The engine needs to be warmed up gently so that the oil has a chance to circulate to the cylinder head and the gearchange is an acquired art, but the big vertical twin’s always gusty, still able to cruise along at 90mph without exploding.
The CB450 combined a 180 degree crankshaft with a unique cylinder head design - torsion bars replaced the normal valve springs, working through rockers; the DOHC’s themselves acted on another set of rockers, which sat on eccentric shafts for ease of valve clearance adjustment. This required a rare degree of engineering precision in the sixties, so much so that each set of valvegear components had to be matched; mess them up and you’ ll end up with a crankcase full of bits!
The whole point of the exercise was to remove valve float at high revs, although it was soon rendered pointless by advances in valve spring technology. The CB450 engine can be safely spun to 10000 revs, even twelve grand doesn’t cause it to explode although by then power has done a runner.
Because the engine lacks any balancers, the torque reaction thrums away a little at low revs, but come six grand the power flows in hard and the mill smooths out. 90mph cruising is relatively relaxed! Don’t be put off by rough running examples, that’s all part of the package but look instead for the power punch at six grand and check the engine breather for signs of smoke.
Ultimately, the engine goes down from ruined small-ends, which are part of the con-rod material, which in turn can’t be removed unless the crankshaft, with its four massive roller bearings, is pressed apart. A seriously expensive job. The best deals are early seventies models which turn up as grey imports from the States at £1000 to £1500.
It would be easy to confuse the CB500T with the 450. Basically, the engines are identical except for a longer stroke on the bigger bike. Alas, somewhere along the line something went very wrong with the engineering quality of the 500, having displayed piston, bore, valve and even crankshaft problems at low mileages.
Anything that has survived is probably well sorted (a bit more blood and guts can be extracted by using CB450 cams). Minor suspension upgrades sorts most of the handling horrors and a 2-1 exhaust does wonders for the appearance as the “classic” shape has aged quite well. A very useful hack at £500 to £750 but don’t take them too seriously.
Ultimately, the engine goes down from ruined small-ends, which are part of the con-rod material, which in turn can’t be removed unless the crankshaft, with its four massive roller bearings, is pressed apart. A seriously expensive job. The best deals are early seventies models which turn up as grey imports from the States at £1000 to £1500.
It would be easy to confuse the CB500T with the 450. Basically, the engines are identical except for a longer stroke on the bigger bike. Alas, somewhere along the line something went very wrong with the engineering quality of the 500, having displayed piston, bore, valve and even crankshaft problems at low mileages.
Anything that has survived is probably well sorted (a bit more blood and guts can be extracted by using CB450 cams). Minor suspension upgrades sorts most of the handling horrors and a 2-1 exhaust does wonders for the appearance as the “classic” shape has aged quite well. A very useful hack at £500 to £750 but don’t take them too seriously.
The same scepticism should be applied to other Honda twins of the period - CB360, CJ360, etc. They lack the quality of Honda’s sixties designs, should only be considered as cheap and cheerful hacks. The sixties twins - 250/325 Dreams and a host of smaller stuff - are all too old to be of serious use; when they are genuinely immaculate they are also considered classics and therefore expensive.
A bike which can trace its roots right back to these old Hondas is the Kawasaki GPz305. This is as plain and simple as vertical twin engineering gets, with resulting excellent performance, economy and handling. Alas, the engine shared early Honda twins penchant for not getting sufficient oil to the cylinder head when warming up and also had disturbing crankshaft problems.
Engine life is highly variable. Some owners sing their praises to great heights, others curse them violently. As far as buying a used one goes, the main problem is that the engine can go from seemingly fine to a bag of nails in a very short period of time. A lot of luck’s involved in finding a good one that will last well.
The chassis is built down to a price, corrodes nastily over our winters with the usual naff calipers, disintegrating exhaust and rattling chassis bearings. Loads of spares in breakers, so not that expensive to fix. In 1996, its last year of manufacture, there were some deep discounts on new ones, as little as £2500. There’s no reason to pay more than £1500 for recent stuff and it’s possible to buy a hack for less than 500 sovs.
Another bike with generally splendid performance but a potentially expensive engine’s the XS500. This combined an 180 degree crank with a chain driven balancer, which when all was set to perfection provided good power, reasonable economy and vastly superior handling to the XS650, which was sold at the same time.
The price paid for the relative complexity, which included DOHC’s and eight valves, was an engine that could die, especially when thrashed, without much warning. Age isn’t kind to them, either, with alloy rot turning minor operations into major traumas - corroded in screws, for instance, tend to snap off or tear the threads out of the engine. Even changing a spark plug can result in having to rip the head off to do a helicoil. And the XS500 is one of those engines that never runs happily once it’s been disturbed. Spares are also rare on the secondhand circuit, any potential engine failure turning out expensive.
The chassis, though, is a good one, based on Yamaha’s racing experience with its RD strokers and worth reinventing by fitting a motor from a different model. Some dealers try to off-load XS500’s for as much as £1500 but given the engine troubles paying more than £500 is plain silly.
There’s a huge range of vertical twins out there. Everything from 125cc hacks to prime meat TDM850’s. The whole reason for going for a Vertical twin is its relative simplicity. When it gets too complex it loses its reason for existence. Because so little development of the breed has taken place (even our esteemed editor has worked out two ways to eliminate their vibration without loss of power or efficiency...) the whole market’s still wide open.
The choice of best buys depends on what you want. For laid back riding go for a grey import XS650; just don’t expect too much speed. For good overall performance chose a GPz500; if you can afford it go for the later 17 inch wheel version as it’s much less likely to throw you down the road. For real practicality together with some blood and guts, chose an early seventies CB450, again on the grey import circuit. If you want to keep the replicas in sight and don’t mind doing a little work to its chassis, then the TDM850’s the only game in town.
Dick Lewis
A bike which can trace its roots right back to these old Hondas is the Kawasaki GPz305. This is as plain and simple as vertical twin engineering gets, with resulting excellent performance, economy and handling. Alas, the engine shared early Honda twins penchant for not getting sufficient oil to the cylinder head when warming up and also had disturbing crankshaft problems.
Engine life is highly variable. Some owners sing their praises to great heights, others curse them violently. As far as buying a used one goes, the main problem is that the engine can go from seemingly fine to a bag of nails in a very short period of time. A lot of luck’s involved in finding a good one that will last well.
The chassis is built down to a price, corrodes nastily over our winters with the usual naff calipers, disintegrating exhaust and rattling chassis bearings. Loads of spares in breakers, so not that expensive to fix. In 1996, its last year of manufacture, there were some deep discounts on new ones, as little as £2500. There’s no reason to pay more than £1500 for recent stuff and it’s possible to buy a hack for less than 500 sovs.
Another bike with generally splendid performance but a potentially expensive engine’s the XS500. This combined an 180 degree crank with a chain driven balancer, which when all was set to perfection provided good power, reasonable economy and vastly superior handling to the XS650, which was sold at the same time.
The price paid for the relative complexity, which included DOHC’s and eight valves, was an engine that could die, especially when thrashed, without much warning. Age isn’t kind to them, either, with alloy rot turning minor operations into major traumas - corroded in screws, for instance, tend to snap off or tear the threads out of the engine. Even changing a spark plug can result in having to rip the head off to do a helicoil. And the XS500 is one of those engines that never runs happily once it’s been disturbed. Spares are also rare on the secondhand circuit, any potential engine failure turning out expensive.
The chassis, though, is a good one, based on Yamaha’s racing experience with its RD strokers and worth reinventing by fitting a motor from a different model. Some dealers try to off-load XS500’s for as much as £1500 but given the engine troubles paying more than £500 is plain silly.
There’s a huge range of vertical twins out there. Everything from 125cc hacks to prime meat TDM850’s. The whole reason for going for a Vertical twin is its relative simplicity. When it gets too complex it loses its reason for existence. Because so little development of the breed has taken place (even our esteemed editor has worked out two ways to eliminate their vibration without loss of power or efficiency...) the whole market’s still wide open.
The choice of best buys depends on what you want. For laid back riding go for a grey import XS650; just don’t expect too much speed. For good overall performance chose a GPz500; if you can afford it go for the later 17 inch wheel version as it’s much less likely to throw you down the road. For real practicality together with some blood and guts, chose an early seventies CB450, again on the grey import circuit. If you want to keep the replicas in sight and don’t mind doing a little work to its chassis, then the TDM850’s the only game in town.
Dick Lewis