In the sixties Norton, Triumph and BSA were all deadly enemies, each with their own virtues and devotees. Norton had the best chassis, Triumph the superior engines and BSA were somewhere between the two. Perhaps typical of British engineering at the time, when they were flying high on an excess of sales and lack of big Japanese rivals, there seemed little point in investing in new machines. And when things began to fall apart, there was sod all money to renew the ancient machine tools and invest in decent designs. First BSA merged with Triumph, then there was Norton Villiers Triumph and in the end just poor old Meriden knocking out 750cc vertical twins.
Along the way there were attempts at modern bikes. The Trident wasn't really any worse than the Honda CB750, save that it lacked an electric start and front disc brake... and sometimes had dodgy valves and poor build quality. A well put together T150 or T160 is still an interesting motorcycle that can be very useful, unless, of course, you've ridden a new 900cc Trident. With the new Triumphs doing well, making the old triple seem obsolete most of the attention, nay devotion, has turned to the old OHV twins (especially now that it looks like Triumph won't be building new Bonnies).
My own Bonnie is a sensibly modded 1972 job, one of the last drum braked 650cc models but with the then new frame with the oil in the upper tube. It shares garage space with a Norton 750cc Commando of the same era, an Interstate model with Superblend bearings and electronic ignition. Both machines run stock but renovated chassis and are still used as often as ever.
The history of the 750cc Commando's engine goes back to their 500cc unit. In the late sixties Norton found themselves with the Atlas, whose 750cc's produced such a terrible flurry of vibration that it was almost unusable. This may have had something to do with using the same crankshaft as the 650 Dominator, the big capacity route being the cheapest way of upgrading British bikes to compete with the Japanese - in fact, the process so stressed their engines that they lost most of their ruggedness and charm. Anyway, faced with a market that demanded speed above all else and an engine that tried to shake itself out of the frame, the now infamous Isolastic mounts were born. The engine still shook, to the extent of often destroying its mounts, but most of those vibes were absorbed by the engine mounts.
The famous Featherbed frame was junked in favour of a new tubular trellis to match the engine mounts. As the whole engine was isolated it meant the swinging arm was not mounted directly on the frame! The handling depends entirely on how well the lsolastics are set up. Just as the Norton really needed a new engine design but got, instead, a new chassis, so the Bonnie was supplied with a new frame when the old one had evolved quite nicely over the decades from a speed wobbler into a relatively stable device. The Triumph frame was supposed to be common to the BSA twins, although in reality Triumph had insisted on retaining their swinging arm mounts between frame rails and back of engine, so even the savings from common running gear couldn't have been that high. The one downside of this chassis was a tall seat height that left the rider perched high on the bike - a most un-British trait!
The Bonnie makes up for this with a gutsy engine. 50 horses at 7000rpm is nothing to write home about, but these are real British horses rather than the effete Japanese ones, with a direct connection between the throttle action and the way the bike accelerates. With 400lbs of mass, many a modern Jap has been surprised by the way it'll accelerate up to 80mph, although top speed is only 110mph.
Where the Triumph thrives on revs (at least up to 7500rpm) and revels in being used hard through its gearbox, the Norton is more refined, slightly more restrained, partly because it's fitted with taller gearing than originally supplied by the factory and partly as a result of its extremely long stroke (89mm). Where the Norton really shines is sticking it into fourth gear at 50mph and opening the throttle. A tremendous shove in the back comes streaming in as its torque flows in relentlessly until 6000 revs. Even the factory advised against going above 7000rpm and even though the engine is claimed to produce 65 horses at 6500rpm, I limit myself to 6000 revs absolute maximum. With the taller gearing this gives a top whack of 115mph and a cruising speed, supremely relaxed, of 85 to 90mph.
It's possible to cruise the Bonnie at a similar speed but the engine feels very lively, with some quite strong vibration blitzing the chassis. For long life 75 to 80mph is much more sensible. Both bikes have plenty of power in hand for further, brief bursts of acceleration, so can just about deal with the motorway hustle.
If I have to do long distance work I usually take the Norton. It's much more relaxed and has a huge five gallon petrol tank (I would not advise anyone to ride far with the GRP version...). One of the best mods I made to the Commando was fitting a single SU carb, an expensive conversion new but I bought a secondhand one for £75. Smoother running, no carb balancing and better economy.
An original bike with points ignition and twin carbs returned 40 to 50mpg. Just fitting electronic ignition gained 5mpg, probably because the stock points varied the timing so much the engine never had a chance to run as it was designed. It was also nice to have the engine come to life first go, as a hell of a hefty kick is needed. With the taller gearing I was getting close to 60mpg. The SU carb improved that to nearly 70mpg! As I limited revs to 6000rpm there was no real loss of power.
The Bonnie was rather surprising with regards to fuel. Ridden gently it would turn in 75mpg, most of the time around 65mpg was available. Thrashed it would go down to 50mpg but riding like that I was more worried about the engine blowing up than the way the fuel was going west. The twin Amal carbs didn't need much attention so I had no real inclination to turn the engine into milder Tiger spec.
The Bonnie was brilliant on both country and A-roads, or anywhere with lots of curves. The sidestand prong has to be cut off, otherwise it'll dig in and try to throw the bike off the road. Vertical twins have always had the edge over triples and fours because their engines are narrow and can be thus mounted low, and the Bonnie is deliberately set up for highway kicks. Although the Norton only has an extra inch in wheelbase over the Triumph's 56 inches, it feels much more lazy, much better suited to the faster A-road and motorway curves. It feels slightly less natural than the Triumph, but with the lsolastic mounts firmed up is more stable, less affected by road bumps or white lines... both machines were shod with Avons on 19 inch wheels, tyres lasting a couple of thousand miles longer on the Triumph, but as even the Norton does over 12500 miles it's hardly a great load on the wallet.
Wheel bearings were crap on the Triumph, though. It came to me as a five year old with only 6000 miles on the clock but took only another 1000 miles to have the back wheel bearings rumbling. I had a look at the front at the same time, ended up replacing them as well, there being a distinct lack of grease. There seemed little point trying to buy bearings from a Triumph dealer, given their poor history, so I was quite pleased to buy a pre-greased set that were sealed on both sides. I haven't had any trouble since.
I also had the back wheel break up. I was two-up with an overweight wife on the back (ouch...) and a ton of camping gear in top-box, panniers and tank-bag but having half a dozen spokes go ping simultaneously in the middle of the Scottish highlands had me cursing the Bonnie and then walking five miles to a phone box to summon the AA. By the time I got back the guy had turned up and was tying down the bike on the trailer whilst the wife mouthed off about my total ineptitude.
I usually took the Norton touring as I never had any qualms about the robustness of its chassis but it had inconveniently decided it wanted a valve job, something it did every 10000 miles or so. Mostly down to the poor design of valve guide wearing out quickly and letting the valves wobble about. There was some warning of this, with banging in the still original silencers and a haze of pollution on the overrun. Valves needed a 500 mile adjustment even when they were in good fettle.
Amusingly (from a distance) the vibes from both engines destroyed the exhausts but in different ways. The Norton's downpipes would actually crack up although the silencers survived intact. The Triumph would crack up the brackets between downpipes and frame whilst also cracking up the silencers, although as they were of the quick rot variety it might have been a combination of rust and vibration. The Norton caught me out miles from home but I effected a repair with jubilee clips and a couple of cut up tins. Inelegant but it lasted the 220 miles back to my house. The ultimate solution is ultra thick stainless steel downpipes!
Both engines needed regular bolt tightening sessions unless you want to amuse the general populace with a loose cylinder or oil gushing out of the cylinder head. Triumph's valve covers are notorious for twirling off but drilling and wiring them together stops that (until the wire breaks) and the Commando's chaincase is renown for spewing out oil.
The Norton engine had retained its pre-unit construction while the Triumph had combined engine and gearbox in one unit in the early sixties. There's no real disadvantage in having a sepatate gearbox. Neither bike has had any gearbox troubles but the ease of removal of the Norton's would obviously be a plus point if, or when, attention is needed. The good thing with a four speeder is that the gears are large and thus long lasting, and in both cases the oil is kept separate from the main engine supply, allowing it to be suitably thick. Missed changes were never a problem on either bike. The Triumph's change was a touch faster, matching its harder revving engine, but the Norton's had a cleaner downchange. I never did, and doubt if I ever will, try a clutchless change on either bike.
The Norton has done the greater mileage at 76000 miles, against a mere 52000 miles on the Triumph, but has received more attention. Not by me, though, the bike came to me with 22000 miles and a recent, complete engine rebuild that included electronic ignition, hefty main bearings and its first rebore. Apart from the aforementioned head jobs I did another re-bore at 47000 miles and fitted new triplex primary chains every 12000 miles. The diaphragm clutch went the once at 39000 miles, producing a lot of clutch slip and some disturbing noises. Most parts are still available from the Norton factory. Use of modern gasket goo has stopped the worst of the oil leaks, although there seems nothing that can be done with the chaincase.
The Triumph is on its final rebore, third set of valvegear but still runs the original crankshaft. The duplex primary chain is longer lived, but the tensioner also needs replacing at 15000 miles. The clutch, a rather more conventional item than the Norton's, needs new plates every 20000 miles but if cheap pattern plates are used then it'll need attention in a lot less than 10000 miles. On both bikes, it's important to put high quality parts inside the motor.
The same should go for the chassis as well. I once fitted some cheap pads in the Lockheed front disc. After about 200 miles they broke up when I braked from 40mph for a junction. I had to lock up the back wheel and pop the bike into first gear to pull up in time. Even under that extreme abuse the chassis retained its poise. Unflappable was its best description. The rear drum was a delight to use and didn't wear out its shoes for tens of thousands of miles. When set up properly, with decent pads and Goodridge hose, the front disc was adequate to the Commando's speed but a little bit wooden in feel. The lack of feedback intensified when the brake fluid went off or the pads, which lasted about 8000 miles, were near the end of their life.
Wet weather wasn't exactly fear inspiring, but if a light caress of the lever every few minutes hadn't removed the layer of water then there was a mind dislocating period of lag before they gripped. When they did grip they did so progressively enough to avoid locking up the wheel on a wet road.
The Triumph's drums were a bit of a mixed bag, as well. The conical hubs were a beautiful sight to behold, but the front had a curious push-pull operation of its TLS unit that needed meticulous attention to its adjuster every 500 miles and a newish brake cable (figure about 5000 miles). When it was set up well, the braking was fierce-enough to lock up the wheel but sensitive enough to be really nice in the wet. When it went off, it became grabby in the dry and very unpredictable in the wet. The rear drum had no such suicidal tendencies but could have done with a touch more feel. Shoes lasted about 12000 miles at each end. Overall, | preferred the Norton's setup, but there wasn't enough in it to make it a reason for choosing one machine over the other. It's possible to fit the older TLS drum front brake from the late sixties version of either bike, so if they really become too dodgy a relatively cheap and effective solution is at hand.
Suspension was similar but different.
Both machines had a set of Girling shocks, although the canted forward nature of the Norton's gave a more supple ride than the near vertical Triumph's which often seemed rather harsh. The Norton certainly had the better forks, inherited from their acclaimed Roadholder series that had good damping and perfectly matched springing. Again, the Triumph front end was less sophisticated, giving the bike a rougher, edgier feel on today's ruined road surfaces. Not that it was ever bad in the sense that it let the Triumph wobble or weave, but jumping from one machine to the other showed that the Norton had a more sophisticated ride.
With its slightly dubious shimming of the Isolastic mounts the Norton needs all the edge it can get. The shims needed attention every 2000 to 3000 miles, depending, it seemed to me, on how heavily loaded was the chassis. Both sets of forks eventually wore out. It was relatively easy to buy new bushes and seals for the Norton but I ended up buying a new set of forks for the Triumph. The latter felt less assured on knackered forks than the Norton.
Both machine's electrical systems have evolved in an identical manner. With the exception of the alternator, all the Lucas electrical bits have been pulled off and thrown away. Replaced with some Japanese solid state bits, I'm sorry to say, and a big car battery. Lights are halogens but the Norton's lasts twice as long, which reflects the amount of vibration getting through to the chassis. Switches, electrics and wiring on the stock bikes are total crap after a couple of years wear and should be junked in the unlikely event that it hasn't been done already.
Both bikes have a voracious need for oil, the Triumph having a slight tendency to crack its frame, letting oil leak out of its reservoir. The oil cap in the frame (at the front of the seat) is actually a valve cover - cynics might suggest that it can be used to replace one of the valve covers when they vibrate off but this would leave you with a lap full of lubricant! Because a lot of oil's burnt off or leaks out I only change it every 3000 miles, which seems about right for these motors which have only the most basic of lubrication systems.
If I had to chose one machine then it would probably be the Norton as my riding tends towards the long distance. If I was going to use one of these bikes for commuting and charging down country lanes then the Triumph would have the edge. Prices for a good example of either are in the thousands rather than hundreds with the venerable Interstate fetching an extra grand over the Triumph, running if rough examples of which can be bought for about £750. But they will need two times that amount spent to bring them up to scratch. The great pity is that there is no modern interpretation; a fun big twin with an excess of torque that can be run on the same kind of money as a Honda C90.
Tom Laing