NORTON 650SS
Everyone loves 650 twins. Everyone loves Norton’s featherbed frame. Frank Westworth tackles a thorny issue
Mention the word ‘Norton’ and almost everyone thinks ‘Ha! Commando!’ If they’re modernists they mean the current machine of that name, if they’re of a more traditionalist bent, they drift off into featherbed fantasies. Then confuse things by saying that in your view the best featherbed Norton twin is the 650, and watch them puzzle for a moment then lighten up with the memory of the 650SS. In fact… in my view the best 650 Norton had but a single carb and wasn’t sporting at all, not really. But I digress into personal stuff here: the feature machine is that out and out sportster, the 650SS. Twin carbs and a tacho and everything.
My memories of riding these machines are not entirely positive. Back in those rose-tinted Seventies, I shared a flat with one. Well… with its owner. I chose that word with care: he owned it. He rode either a BSA C15 or a Kawasaki triple. A 250, which we all agreed was unfairly fast and no one but a lunatic would ever want more performance. Our pal down the road with the Combat Commando agreed. His Commando was more reliable than the 650SS and a lot faster, but it was no faster on the Norfolk twisties than was the Kawasaki. Strange but true. And yes, we swapped riders, too.
The reason Barrie rode either of his rather divergent 250s was because every time he took out the 650SS it broke. All sorts of creative things fell off. Like the exhaust pipes. They also broke if you tried to ride fast enough to keep up with the Commando on a weekend jaunt to Snetterton, for example. If you were lucky, that is. Because if the exhaust pipes didn’t fracture or fall off then the head gasket would blow. They did this a lot. Those were dark days, fashionable nostalgia notwithstanding.
My buddy even painted the Norton in a bizarre shade of 1970s metallic green, hoping that the cheery hippy spirit would calm its errant ways. The next time he took it out for a spin, the left-side exhaust fell off, pivoted around the silencer clamp, went under the rear wheel and threw him off. After that? The Kawasaki. Let the good times roll.
Rather more recently, I borrowed another – immaculate – 650SS for an RC feature (November 2009, as you ask) and after an afternoon’s hooning around Somerset I returned it to its happy, smiling, ever-optimistic owner. His smile slipped only slightly as the strangely single-cylindered twin rolled noisily back into his drive. Another head gasket. What is it with 650 Norton twins and their head gaskets?
Grim experience down the very many years with very many Norton twins – most of them Commandos – has revealed that they do have a vaguely alarming tendency to blow chunks out of their head gaskets. This is rarely publicised,
but has been true down the many years of my experience. There was also one common denominator (Oh! A joke! That was a Norton Dominator joke! OK, never mind…). And that was? One or two of my own Norton twins were untouched mechanically in the engine dept since the skilled fitters at the factory built them, and they didn’t blow their gaskets. That was the first clue. Actually it was the second clue, the first being that whenever I replaced a blown head gasket – always with whichever sort was recommended by the NOC – I struggled with the strange downward-facing studs Bert Hopwood used beneath the inlet tract and exhaust ports. The nuts for those studs were always butchered or stripped or both. It was really difficult to find a spanner to tighten them properly, and in the end a friend made me a tool for the studs beneath the exhausts. After that … no more blown gaskets.
You will be delighted to learn that this latest test 650SS failed to blow up. In fact, it ran with boring perfection, proving once again that if an engine has been assembled by someone who knows what they’re doing, then the chances are that it will do what it does for longer than an engine built by an ape using cheap rubbish parts and the wrong tools. This should be no surprise to any of us, but folk still argue with me about it.
The 650SS, then. What is it and where does it fit into the Norton twin chronology? Would I like one, would you like one, and is this the best Norton twin? The last is easiest to answer, at least in this scribbler’s opinion. It’s not the best of the Dominator twins, although my own favourite ‘best’ is in fact another 650 – the Mercury. I would snap up one of those today. And sadly… so would too many other people for them to be cheap any more.
Norton’s range for 1961 included a 650 for the first time, lining up that machine alongside 500 and 600cc versions of the Hopwood twin. Unhappily for some, that machine – the Manxman – was intended to be export-only, export in this case meaning mainly for the US market. Britain still needed those export dollars. The engine’s stretch was actually to 646cc, and was achieved by lengthening the stroke over the earlier 600cc 99 engine from 82 to 89mm, while leaving the bore unchanged at 68mm. Only a year later – remember that this was the age of the ‘white heat of technology’ – the bore was increased to 73mm, producing the 745cc Atlas. Who said that the old industry wasn’t capable of radical engineering? Why, in less than fifteen years, the original 500 twin had grown all the way to a 750. White heat indeed. Incandescence, almost.
The 650 engine was still instantly recognisable as a descendant of the 1948 original twin, despite many years of steady development. The hefty crankshaft still drove the single camshaft and ignition system by two short chains, and the cylinder head was still the large, complex design which cast the rocker boxes as part of the cylinder head itself, rather than as bolt-on extras as was the Triumph way, right from Turner’s original all the way to their final demise in the late 1980s. Norton also cast their pushrod tubes as part of the barrel, plainly aiming to avoid the Triumph lube leak problems. Part of that laudable aim for lessening lube loss was the array of fasteners holding down the cylinder head – although that brought woes of its own, as already discussed.
Part of the 650 engine’s development
involved the introduction of a revised cylinder head employing race-bred ‘downdraught’ inlet tracts, which was touted as being A Big Thing. Perhaps it is, although I struggle to understand how raising the carbs above the inlet tract improves the engine’s performance. The idea of updraught carbs is easier to understand, as there’s little likelihood of flooding the cylinder that way, but… If you’re borrowing one of these machines, try to remember not to tickle the carbs much … if at all.
The rest of the Norton is exactly like the rest of the Nortons in the range. One of life’s many oddities is exactly why Norton made it so difficult to instantly identify their various models. Park an Atlas and a 650SS side by side and you need to be an expert anorak to tell them apart. I mean, you and I may know that the engine breathers are different and that the early 650SS mounted the speedo in the
headlamp shell and the tacho out on a limb, whereas the Atlas carried both instruments on a single bracket, but that’s not too exciting in the café car park vanity contest.
However, the frame is the famous featherbed, complete with short Roadholder forks and decent brakes. This particular example is still fitted with the factory original 8” sls stopper up front, which is no bad thing. Although fashion prefers the Commando or aftermarket 2ls conversions like those from John Tickle or Paul Dunstall, in fact the sls anchor is often as effective as the 2ls device. It shouldn’t be, and maybe it depends on the vigour of application, but this one works very well. Rather better than the Commando 2ls brake fitted to my own Matchless CSR twin, which uses the same forks and wheels. Strange but true.
Norton had followed the move away from dynamos, replacing their Lucas items with crank-mounted alternators as did the other British bike builders, but they persisted with magneto ignition long after the majors – BSA and Triumph – had shifted entirely to coils This is still the case with this machine, the magneto fitted carries the little red badge announcing that it’s a ‘competition’ item, although in all seriousness I doubt that matters these days. Like the red HT pick-ups, I doubt that performance is enhanced much by an alleged ability of the magneto to run underwater for a while.
And because the 650SS carried that ‘SS’ tag, of course it was fitted with twin carbs; a pair of Amal Monoblocs in this case – and a pair still grace the featured machine. Triumph, and indeed BSA and other companies which felt a need for the supposed speed advantage offered by twin carbs, tended to redesign the
cylinder head – or at least the inlet manifold – to make room for the seriously asymmetric Monoblocs, but Norton didn’t do this. No, rather than introduce a splayed head, splayed to make space, Norton kept their inlet tracts parallel, instead using a version of the carb which had no float chamber of its own.
Take a close look, you’ll see that the Norton has no right-hand fuel tap, just a single tap on the left. This feeds fuel to the left carb, which has the traditional left-side float chamber. The carb on the right, however, has no float chamber – a variety usually described as a ‘chopped’ Monobloc. So, the fuel feed to the right-hand cylinder is controlled by both the flow through a single tap and by the level of fuel in the carb feeding the carb on the left. Why did Norton do this? Especially as Amal supplied Monobloc carbs with their float chambers on the right to BSA, among others. Curious. I have asked all manner of expert-leaning fellows but have never heard a convincing explanation. If you know the answer, feel free to share!
When those first, early 650 twins hit stunned US showrooms, they were fitted with pistons offering a decently sporting 8.3:1 compression ratio, but that was raised to 8.9:1 a year later. If ever an engine would have been driven to drink the old 5-star petrol, this was it. And although there’s no sure way to work out which pistons are inside an engine which will certainly have been rebuilt more than once in its lifetime, the amount of heft required to kick the thing over suggests that these are decently highly compressing items. However, that said, it didn’t pink (pre-ignite, for those too young to recall the joys of pinking).
Which brings us neatly around to starting the bike. As always, borrowing a machine from Chris at Venture Classics brings with it the enthusiastic loan of a strong foot. Which is just as well, as my own kicker is struggling increasingly with big twins. This started fine,
though, and chatter with Chris revealed that he’s also reaching a point at which he prefers starting big singles, which at least usually have a decompressor fitted. This is somehow reassuring.
We also pondered the joys of ‘originality’. Although this machine is blessed with those essential matching engine and frame numbers, it spent a decent part of its life fitted with an Atlas engine, preferred by some for its lower (7.6:1) compression pistons, and considerably more beefy bottom end grunt than the 650SS. The SS tries very hard to live up to that ‘Super Sports’ tag, being an engine of two parts: fairly familiar and unremarkable trad Brit 650 until around 4000rpm, where it endures something of a transformation, becoming more harsh, clattery and vibratory the more you rev it. The rasp and rattle accompanies a noticeable step in the power band and the SS does indeed pull like a bike apparently developed from the factory’s production racers. Only you know whether this is important to you. I suspect that most riders of machines of this kind will not discover the high performance available, but it might of course be enough to simply know that it’s there should you want it.
This engine’s nice and quiet at ‘classic’ revs, and even ticks over dependably too. It all sounds so civilised, with no real hints that if you need it to, the bike can go very fast indeed. And it can, the quoted 49bhp at 6800rpm being more than enough to bring a little excitement into your life – remember here that the SS weighs in at 398lb, only 8lb more than the 500cc 88SS.
The gearing was raised by changing from the smaller machines’ 19-tooth (88SS) or 20-tooth (99SS) engine sprockets, lifting the 650 to 21 teeth. Not a shattering amount, but sufficient to raise the probable top speed to around 120mph under favourable conditions.
Which brings us back to the brakes. This is a seriously rapid machine, and although the sls 8-inch front brake is one of the best of its type, I’d not want to try to haul up from ton-plus, to be honest about it.
But if there’s a cautious question mark hanging over the braking, there’s no such thing when it comes to the handling. This is a featherbed, and you know it as soon as you sit on it, mainly because of the width of steelwork at the nose of the seat. You also know it as you hit your first decently quick corners, where that traditional and indeed fabled featherbed handling is guaranteed to raise a smile. Modern rubber – Avon RoadRiders on this machine – works well with the fabled frame, and you’ll deck the centrestand or your boots at will. It’s great!
Unlike the riding position, sadly, which is that strange but entirely familiar Brit; forward feet and flat bars. I’ve never liked it. My own only featherbed Norton – a pedestrian Model 50 – has much more comfortable and higher bars, making it far more pleasant to ride for any distance. The 650SS I rode back in the 1970s – there might be a pic nearby – was fitted with rear set rests to match ‘Norton flat’ bars, and that was a lot better. However, top dollar goes to stock bikes these days, so if you want the comfort afforded by better footrest locations you’re going to pay more than once for the mods required.
Starting the SS is actually OK – but you do need to remember not to over-tickle the carbs, it is too easy to flood things because of that downdraught head. The right-hand‘ chopped’ carb’s tickler is not entirely easy to reach, and … if I owned one of these I would fit a single carb manifold. As soon as the engine’s up and going, though, happy rider gets the opportunity to admire the gloriously flickery Smiths chronometric tacho, perched out on its limb above the bars. Hours of fun, fascination for all the family.
I’m not even going to mention low speed riding, because no one sensible buys an SS to potter gently down leaf-strewn muddy lanes in winter. Get out onto the roads a little and stretch the wire a little. And it works – as a complete machine rather than a collection of parts. It really does. You can hammer along, with Mr Hopwood’s beefy twin making all the right noises and making reasonable progress too, in absolute terms, not just old-bike standards. An easy A-road hauler – if you can tolerate the strange and entirely unsporting and unsupportive riding position.
The engine, though. Hmmm. Norton intended this machine to be a Bonnie beater, and on paper this ambition appears to be achievable. As I’ve already said, the Norton puts out 49bhp to power its 398lbs, while a contemporary Triumph T120 delivers 46bhp, but weighs in at 363lb – in theory, their real-life performance should be much the same, with the Triumph having an edge on acceleration. Except…
Except it doesn’t feel that way, not out on the real roads. The Bonnie feels altogether faster. It certainly sounds faster, and it feels as though you’re covering the ground faster than aboard the Norton, which feels less willing to rev and heavier than its stated weight. It’s curious. The T120 develops peak poke at 6500rpm, with the SS aiming a little higher at 6800rpm – except the Turner twin revs willingly and hard past its peak power point, while the SS becomes increasingly unwilling before it gets there. Suddenly, it becomes clear why so many converted their Nortons into Tritons…
Time marches on. You get older, your knees creak. As winter approaches you look for some sort of affordable, practical, interesting bike, one which would benefit from your years of spannering experience. Ideally, a bike with electric start and old enough to satisfy the VMCC 25 year rule.
I have always rated the new generation of super-scooters. They’ve plenty of power, are swift, automatic, economical and provide oodles of room to carry almost anything you would want while out on the road. I’ve owned both Honda and Yamaha versions. Both were very capable… BUT (there is always a but) their suspension, although sophisticated, just cannot cope with bad road surfaces. I do most of my general riding in the Yorkshire dales and the Pennines, and explore all manner of little roads and tracks which generally have poor road surfaces. Motorcycle-size wheels give a much better ride but I like the automatic gearbox, good brakes and economy provided by the super-scooters. So what are the cheap alternatives?
At the back end of 2015 I spotted an interesting Honda. I have a soft spot for early Hondas, so I read on. The advert referred to the sale of a 1979 Honda CB400A Hondamatic. I’d heard of them in the dim and distant past but had never been close to one. It certainly sounded like an automatic, has big wheels, a nice seat and looked as if someone has done quite a bit of work on it. Perhaps this had possibilities.
The seller had been let down by potential buyers (so he said), and talked a good fight. I was interested and it was within my modest price bracket. I was advised that he had struggled to get it to run properly, but it had run and everything was working apart from that glitch. Fair enough. A bit of electrical work never phases me so a deal was done. The seller agreed to deliver it and I became the new owner a few days later.
In the meantime I did a swift bit of research on these models. They came into the UK in 1978/9, together with 250 and 400 manual versions. They all were 360-degree parallel twins with twin Keihin carburettors. Sales for the 400 Hondamatic versions were not good and, as far as I can make out, they were only imported for a six month period. Dealers heavily discounted them to make a sale. The British public was not ready for such a departure. The 40bhp manual versions developed very quickly into the Superdream and ran for many years, but the CB400A Hondamatic was done by 1981 in the UK. Most of them ended up in the USA until 1984.
The concept of the Hondamatic is that the engine was detuned to about 30bhp. The 400 parallel twin engine drove through a torque converter, into a two-speed manual selected gearbox, with final drive by conventional chain. Gears can be selected on the run without the need for a clutch.
The maximum torque of this engine, although lower power, is much the same as the 40bhp unit, but it’s produced much earlier down the rev range. There is no clutch, but a parking brake lever sits in its place on the left handlebar.
This type of idea was first introduced by
Moto Guzzi with their V1000 Convert in 1975, aimed at the American market. Honda produced a CB750A also in 1975, with CB400 and 450 versions following. Even Yamaha and Suzuki had a go. I remember in my Guzzi days being tempted by a Convert which lounged, obviously unloved, in a dark corner of a basement in a Shipley Moto Guzzi dealer. The Moto Guzzis still retains a clutch for starting whereas the Honda system does not require one and is started in neutral.
So what did I get? This model was an early 1979 registration and had the Dream-type ‘fat tank’ as opposed to the later, slimmed down version and separate sidepanels. Initial inspections indicated a very clean bike which had obviously been worked on. The paintwork was not original but was roughly the correct colour and it only needed a general tidy up at this stage. All the electrical ancillary circuits worked, but the starter circuit was not running.
I found a Haynes manual and joined the excellent Honda Twins Forum in the USA. There seemed to be plenty of ideas regarding the more conventional manual transmission bikes, but nitty gritty detail about the Hondamatic seemed scarce. Later I did find a copy of the Honda workshop manual on the internet.
Access to the workings of the bike is straightforward and the seat, fuel tank and sidepanels are quickly removed to expose the electrical wiring loom. I had a decent wiring diagram, although the ancillaries are shown in USA style. I first disconnected the wiring to the starter motor and bypassed the control system and – to my delight – the motor turned over
the engine very nicely. So the starter motor and the mechanics were sound.
Then the horror story started to unfold. Uneducated fingers had been at the wiring loom, and I quickly realised that it would be better to start again rather than repair. Decent secondhand spares are available in the USA but carriage costs seem to be high. I found an almost new loom there and I quickly ripped out the old and fitted the new. While waiting for the loom, I checked over the twin CV Keihin carburettors which were very clean. These were 32mm items as used on the manual version, rather than 28mm units which were fitted to the automatic. Further checking showed that the cylinder head was identified as an H4, when it should have been a HA. The H4 is from a manual, 40bhp motor rather than the HA small-valve head fitted to the 30bhp Hondamatic (and the CB250). Aha! It appears that someone thought they would boost the power output – more on that later…
Back to the electrical system. I checked out all the components as per the Honda technical data without drawing any conclusions other that they were not right. I sought the help of Marcus at Rex’s Speed Shop who determined that the alternator / self generating ignition, CDI unit and the rectifier regulator were all defunct; something he has rarely seen all together.
The Hitachi system originally fitted is a good quality item, but typically the components either went on forever or died in infancy. I suspect my system was fried by the electrical zombie who disembowelled the earlier wiring loom!
Replacing the rectifier / regulator is no problem, but the alternator and CDI system are different from the versions fitted to the manual bikes and are virtually unobtainable. Being a practical lad, I looked at the details of the static timing and advance range, etc, of the manual bike. I couldn’t see much significant difference with the Hondamatic data, except that there was an electrical / mechanical control system made up of relays, limit switches and electronics which sorted out the gear position indicators, safety interlocks with the prop stand down, starter operation when drive is selected, and idle synchronisation. I was certain I could sort that out.
I noticed an old article on the Honda Twins Forum by a guy who must have been in the same situation as me. He fitted a CB400 generator and CDI off a manual bike into a Hondamatic and it worked well. However, the carburettors needed to be set up nicely, with particular attention to idle speed when in drive. The original Hitachi system had an idle synchronisation system.
Many readers may have driven automatic transmission cars, most of which would operate through a torque converter into the automatic gearbox, quite similar to the Hondamatic (effectively a semi-automatic). Like a car, the Hondamatic must be started in neutral. Away it goes and you can now select drive; first or second in the case of the Hondamatic. Usually the car will lurch a bit as drive is taken up, but the idle speed does not drop. It is the same with the Hondamatic and this is achieved electronically by advancing the timing slightly.
The electronics on the manual CB400 do not need this facility, but the static timing and rate of advance are the same values as the second stage of the Hondamatic system, when it’s in gear. So when you use the manual-type electronics, the idle speed of the Hondamatic when in neutral should be set up a bit higher.
That way, when you select a gear the resulting load as the torque converter takes up does not stall the engine. This has to be done by practice and really is not noticeable if you do it right.
On the Hondamatic, neutral is normally only used when starting and for general maintenance on the centrestand anyway. Like the car systems, the bike will creep very slowly in gear and usually you use light braking to stop movement. Having the bike creep slowly in gear is very useful when putting the bike on a hydraulic ramp – very practical!
I went back to Marcus at Rex’s Speed Shop and, after further discussion, he supplied me with a replacement stator, CDI and rectifier kit intended for a manual CB250, while I obtained a correct used alternator flywheel to match. I installed the new system very quickly as it was all pre-wired and plugged and was ready to fit in with my replacement loom. All the original safety interlocks still remain. The prop stand ‘down’ is wired into the ‘park’ circuit on the nacelle to give a bold visual warning, rather than stopping the engine via the CDI system which will stop the engine as soon as a gear is selected if the stand is down. The hand brake lever, which operates the back brake for parking, replaces the normal clutch lever on the left side.
I was ready to start the engine and it fired up almost immediately, sounding as sweet as a nut through the twin silencers and with a nice healthy charge going into the battery. There was no problem starting the engine with the slightly more advanced static timing value. So, time to ride…
On the road, according to the Honda book, first gear is good for up to 50mph and second can take you up to a heady 90mph. That is enough for me and acceleration was more than adequate. But! My bike would not do more than 50mph in second. Why?
On the stand in neutral you could rev the puddings off it, but on the road it would not pull above 50mph. So I consulted the colonies again. A great chap on the forum thought that perhaps the torque converter had something to do with it. Could it be faulty? A black cloud loomed. The Honda book suggested a stall test and gave details of the speed and stalling scenario.
With the bike on the stand, you start the engine and warm it up. Rig up a tacho to monitor engine revs, select first gear, stand on the back brake to lock the drive and wang open the throttle wide open. All hell is let loose for a few seconds, then the engine falters at about 3500 revs. You must immediately shut off, noting the engine revs at that point. Phew! You do it again in second gear.
The torque convertor seemed OK but was a few revs down on the ideal figure. I sourced a low mileage unit from the USA, fitted it, and did the tests again. The second unit was slightly nearer to the book figure but, with hindsight, I think the original unit is serviceable and it’s on my spares shelf. From what I can gather the torque converters are pretty well indestructible.
At this point, fate stepped in. A pal had also bought a Hondamatic, but there seemed to be something wrong with the electric starter. Did it have an HA cylinder head, I wondered? It did.
I suggested that if he wanted to sell it then I’d be interested… and two weeks later I became the owner of another Hondamatic.
Now I had a correct cylinder head and some good spares. This bike was a later 1980 model, designated the Hawk and usually sold in the USA. My one appeared to be a UK bike and had the slimmer fuel tank. Not only are the head, carbs and electrics different, but the pistons are low compression, flat topped as well. As you can imagine, pistons are rare! Fortunately the barrels, pistons and the head were in excellent condition and within the Honda limit specifications. So with a new set of rings, valve seals and springs via David Silver, the first bike was now true to the book… except for a degree of electrical licence and the larger 32mm carbs. Oh, and in the meantime I recovered the seat.
With great anticipation I headed out on the highway and it felt that it was raring to go. Yet although the speed crept up to 65mph, it still was not right and tended to bog down. Oddly, the second bike was also fitted with 32mm carbs and it had been a good runner. Why then did I have problems with my 32mm units?
I stripped down both sets of carburettors alongside each other. All the jets were identical… until I checked the CV damper springs. The springs on the second carbs were much lighter than on my original unit. I swapped the springs to my first engine and it was transformed. It performed spot-on with as much speed as I want, and ran like clockwork although technically it has the incorrect carburettors. Eureka! It took me three months to learn and find my way about the wonders of the Hondamatic. Now to riding it…
The running first bike passed its MoT and shortly after I attended a classic meet at the Ryhope Pumping Station near Sunderland. It was a nice day and a good number of interesting bikes turned up. Returning to my bike, I noticed a slip of paper tucked under the seat strap. It read: ‘I have an original one of these’ with a telephone number. Intrigued, I rang the person and arranged to see his bike… which, it turned out, was for sale.
A shiny 1979 version with the slim fuel tank was wheeled out, in standard condition with original paintwork. It was obviously being well looked after and a runner. The mileage was 20K but it had not done much since 2008, only 240 miles. After all my problems with the first bike, and still having the remnants of the second, a third bike was the last thing I needed. However, I now possessed a fair amount of Hondamatic knowledge and was cautiously optimistic. Bike #3 looked mint. It started OK with the kick start but demonstrated its reluctance to respond to the electric leg, although the starter motor spun the engine over beautifully. This looked like a carburetion problem to me, so a deal was done.
My first job was to clean out the pilot jets and the engine responded to the electric leg straight away. A bit of luck at last.
The #1 bike was parked up while I ran the latest acquisition to give it a real shakedown.
The correct 28mm carburettors were fitted to #3, but it had an annoying problem of cutting out sometimes when just going off tickover when the throttle was opened. All the symptoms of carburettor problems, but it would not go away no matter what I tried. As a last resort I removed the new, pattern HT coil which came on the bike and fitted a standard, secondhand Hondamatic coil. That worked: to this day it has run perfectly.
Consultation with my friend across the water confirmed that the HT primary coil resistance should be less than 1 Ohm and the secondary coil 7 to 8 Ohms. Sure enough, the original FL102-12V Honda coil was within this specification but the pattern one tested 4.3 Ohms and 15.68 Ohms respectively. So beware when buying pattern replacement HT coils. The engine ran OK for the rest of the full range and the problem disappeared when the standard item was fitted.
All my previous experience on ignition coils was for non-electronic systems and these Honda coils resistances seemed very low to me. A coil for a simple points / battery system would have 3-5 Ohm primary resistance and higher currents are present. CDI systems operate at a much lower current level although their output voltages tend to be higher. I’m not an expert on the fine detail of electronic ignition systems but my info is based on experience and good advice.
Anyway, what started as a leisurely winter project turned into a rapid in-depth education on the workings of a Honda CB400A Hondamatic. It extended to four and three machines, all with different problems. The #2 bike was sold for spares and recently the #1 bike departed to a new home. I am left with a standard, 1979 Honda CB400A Hondamatic. It has now covered a few thousand miles troublefree and confirms what a great, comfortable, touring machine they are. Second gear is used extensively up hill and down dale and 90mph really is within reach. The bike feels very balanced and slow riding can approach the standard of top trials riders, because clutch control is not an issue. (Beware though when on moss-covered water splashes not to touch your brakes to slow down – I know!)
There is no slow-speed free-wheeling band like you would experience with a centrifugal super-scoot twist and go system, although slowing down through the gearbox is much less than with a manual machine. Brakes are adequate and progressive and it handles well. It has a hydraulic front disc and mechanical drum rear. Engine vibration is minimal although the three engine chains (cam, oil pump and balance shaft) rattle a bit.
The CB400A’s fuel consumption is usually around 55 to 60mpg, and the range before reserve is about 130 to 140 miles. The slim tank holds just under three gallons. The bike weights 395lb with fuel, and is about the same size as a British 500 twin size – suitable for an ageing 29” leg measurement. Excellent prop and centre stands are fitted.
Something different, indeed!