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~ ~o= A
750SF: LAVERDA'S i~~ LATINLOVELY I~
Switch to the AA for a different kind of breakdown service Unlimited callouts mean we’re there when you need us Tap & track app lets you follow our mechanic to your side We’ll usually fix you within 30 minutes of arrival Upgrade to Smart Breakdown to track engine faults in real time Join many other AA Members in saving over £55 a year with discounts at Hungry Horse, Vintage Inns, IMO and many more
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Breakdown cover from £39: price is for Annual UK Roadside Vehicle Membership. Other levels of cover are also available. Offer is not available for existing Members or at renewal. Cover must be paid by continuous payment method. We’ll use your payment details to renew your cover after 12 months. You’ll receive a renewal invitation beforehand so you’ll have plenty of time to change or cancel your cover. Offer not available in conjunction with any other offer online or in a breakdown situation. If you’re buying online please use the website link specified, otherwise you will not receive the offer. Gift card: please allow 6 weeks from your policy start date for delivery and processing provided you haven’t cancelled your policy. Card is redeemable online so you must have a valid e-mail address. Offer closing date: 31/12/20. Unlimited call outs: repeat call outs for the same fault within 28 days will not be covered. 30 minutes attendance: based on an average of all AA attended breakdowns 1 August 2018 – 31 July 2019. Smart Breakdown and Tap and Track App: subject to network coverage. Member Benefits saving value calculated based on the top 10% of Members by Member benefit redemptions between 01/03/2019 and 29/02/2020. For further information visit: theaa.com/member-benefits. All information correct at time of print September 2020.
LAVERDA SF 750 .......................................
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A couple of months ago, we mentioned that some people can't help buying the same motorcycle over and over again. Enter Paul Miles, who suffered a very bad case of seller's regret. .. A TALE OF TWO TRIUMPHS ..................... 22
Triumph twins, ancient and modern. Are they actually comparable? Frank Westworth has been smitten by a Scrambler and went off on the trail of a Tiger ... THE ONE TO HAVE ...................................
30
If you could choose any version of AMC's single-cylinder 500, there's one single model year which stands out as being the best of the bunch . Rowena Hoseason argues that th is rarely-seen beast is worth seeking out ... ARIEL W/NG .............................................
36
While other British bike builders contributed sidevalve sloggers to the war effort, Ariel's military machine was based on their sporting 350 single. Simon Holyfield reveals the model 's background and its wartime service record BUYING THE BULLET .............................. 44
Paul Henshaw has extensive experience of Enfield's 350 and 500 thumpers, both
British built and of Indian origin. He guides us through the most popular models and recommends essential upgrades to get the best from your Bullet TRYING TRIALS .......................................
52
Searching for the perfect motorcycle for long distance trials , Graham Lampkin built a bespoke BSA.And then a Benfield. And then a Bonda .. . HONDA'S NIGHTHAWK ........................... 56
Chris Taylor found a 25 year-old Honda which, with a fair amount offettling, proved perfect for local rides. Then fate snatched it away from him. So Chris got another one, just like the other one .. . MAKING SPARKS ....................................
64
The development of the ignition system , how it works, and a few maintenance tips. Jacqueline Bickerstaff (aka PUB)explains the fizzicks behind sparkling performance 72 If you've ever wondered what goes on inside a water-cooled Norton rotary engine, be prepared to be amazed as Richard Negus rebuilds one with expertly accomplished insouciance. Part Two: job done! NORTON F1 SPORT .................................
PROJECTWORLDBEATER ....................... 76
Odgie's project to create a compet itive CanAm flat-tracker, based on an old military machine, nears completion. Now he needs to design and fabricate an appropriate exhaust and source a complementary carburettor ...
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FROM THEFRONT Picture this: a beautiful September afternoon, sun shining, temperature temperate, main roads still unusually clogged with city refugees seeking a little solace in the West Country. An etheric message lands from a friend. It suggests coffee and cake at a cafe in Devon, about an hour away in an area with which I am entirely unfamiliar. I consider the glory that is Google Maps, understand where it is - down a minor road off a B-road off an A-road and apparently by the side of a cycle track which was previously a railway track. I didn't even know the place existed. Don't you just love spontaneity? I should have been doing other stuff, but hey - coffee and cake! Pulled out the Triumph, made sure that the phone was charged and set off, allowing extra time for that inevitable getting lost factor, and headed north-east into bandit territory - or Devon, as most folk call it. Entirely thanks to the glory of Google Maps and its equally glorious Street View, I knew exactly what the junctions at which I needed to change tack looked like, and arrived earlyearly enough to get in a sneaky coffee before my friend Dave rolled in aboard his Moto Guzzi. And what a Guzzi! Dropped bars, rearset rests and more chrome than seems healthy . Shine? It did shine. Cyclists stopped to stare - and to ease the leg strains, I suspect, but the effect was the same. The sun continued to brighten the afternoon and our spirits. Other cycling cafe visitors came and went, and there was coffee, much coffee, and also cake, chocolate cake. We chatted away on all manner of subjects, mostly bikes, but lots more besides and quite suddenly two hours had passed (how do they do this?) and it was time to head home . Dave went north, I headed south. Another glorious Devon switchback which I'd never ridden before, beautiful in the evening sun, providing challenges and delight until I swung due west to head home, scratching a little now as the roads became familiar once again. The Triumph was storming along, I was riding better than usual, corner lines were good enough and toes occasionally touched tarmac. Classic stuff. It's too easy to feel low in these strange days, and along with the increase in general unhappiness has come a more critical attitude among so many folk - including several of my own friends, some of whom I'm known for very many years. What seems a little strange - to me at least - is an increasing tendency for folk to criticise the riding of other folk out on their bikes, no matter what the age or style of bike. Today's ride found me sharing the roads with
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a lot of other motorcycles. At some point it felt as though there were more bikes on the road than cars, which is unusual, particularly in the West Country when it's creaking under holiday traffic. There were bikes riding solo - as I was - and bikes riding in groups, but there was no bad riding - none that I saw. All I saw was other riders enjoying the same experience as me. All - hopefully - enjoying themselves as much as I was. So yes, there is a clumsy message approaching here! And worse: it 's entirely predictable, too. And of course the Romans had a phrase for it: carpe diem, they would cry: seize the day! I think this applies today more than ever before . If you're feeling down, fed up with all that's happening, head for the hills, for the lakes, for the forests, even for the beaches. Switch off your phone , leave social media for another time. Park up at a beauty spot and breathe some fresh air, then ride home refreshed. You will feel better for it. Ride safely
Frank Westworth Frank@realclassic.net
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6 I OCTOBER 2020
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LABOURS A coupleof monthsago,wementionedthat somepeoplecan't helpbuyingthesamemotorcycleoverand overagain.Enter PaulMiles,whosuffereda verybadcaseof seller'sregret...
W
Photos by Paul Miles
e've all, I'm sure, regretted selling a bike. In my case it's usually due to the siren lure of something shiny that needsto be in my garage instead. Despite the hundreds of machines passing through my greasy hands there are very few that I truly regret parting with, perhaps just a handful. Two of those were Laverda 750 twins. At one point I owned three of these machines. The first was a full-blown SFCrace replica and possibly the most uncomfortable bike I've ever owned. The other two were the short-lived SF1,featuring the newly uprated big-valve motor and large accelerator pumped carburettors, yet retaining the slightly oldfashioned silhouette of the earlier model and proudly sporting the famous super freni drum brakes. Unlike certain magazine editors , for whom even 38 gently corroding Matchless porridge twins isn't enough, surely no sane person ~
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OCTOBER 2020 I 7
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Few motorcycles have been named after their front brake. The SF is one of a vanishingly small number. We can think of only one, and this is it; super freni indeed
needs more than one Laverda twin? Emboldened with this sudden understanding, I sold the SFC.Its only real advantage over the less glamourous SFs was the extra power, after all. I resolved to also sell one of
The great cliche is that the Laverda engine is indistinguishable from an early Honda. But only in the dark. The Italian engine is quite large, and considerably distinctive
the remaining two 750s. The first was a fully restored purple bike, the other a slightly tatty and well -used black example. The latter also happened to be the best Italian motorcycle I'd ridden. Ever. I even wrote it up for Rea/Classicas a response to Frank's lyrical waxing about, shudder , a brown Kawasaki twin. Yet, in a moment of supreme stupidity, I not only sold the shiny purple bike but also the wondrous black twin; something I've regretted ever since. Despite my ongoing hand-wringing, the owner continues with his refusal to sell it back to me, revelling in my humiliation . Fastforward a decade or so and I found myself riding another large capacity Italian parallel twin. Whizzing along on the Benelli Tornado, I couldn't help but compare it to the much-missed Lav and, with the possible assistance of a rosehued visor, found the Benny wanting. I sold it as soon as I got home and immediately started searching for another Laverda. Fortunately for me, the 'normal' 750 remains the poor relation in the Laverda line-up, and there are usually a number on sale at any given time. The early machines, such as the GTL,Sor even the SF,are generally less powerful, but for the 1973 bikes onwards Laverda had increased the output to a
Generator and starter motor sit either side of the cylinder block, and the tacho is driven from this end of the single camshaft. The mysterious chrome spherical object below and behind the engine is part of the exhaust's balance pipe
Who could resist Laverda advertising? Certainly not Ace Tester Miles!
8 I OCTOBER 2020
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purposeful 65bhp or so. The SF1,powered by this new motor, was still slowed by the beautiful Laverda designed 21sdrums, replaced with twin front discs on the otherwise similar SF2and finally triple discs and alloy wheels on the last of the twins, the SF3. I wanted another SF1,with that addictive combination of superior power and inferior braking! If the new bike could be something less than concours, that would be nice too; I wanted a machine that could just be jumped on and ridden and not something to fret about should it be wet out. And suddenly, there it was. A 1973 Laverda SF1,in long term ownership and in seemingly excellent condition. Even better, a previous owner was none other than Tim Isles, Laverda nut and author of a definitive text on the SFC.The list of modifications read well, too. Another Laverda giant, Phil Todd, had built the engine with Carillo rods and high compression pistons fitted to the rebalanced crank, along with a ported head, lumpy camshaft and uprated clutch. Sparks were now electronic too and the motor appeared to be, on paper at least, a match for even their mightiest twin, the
legendary SFC. The riding position of the SF1 is perhaps best described as 'sportingly normal ' - think Norton Commando Roadster. A plush dual seat and just aft of centrally mounted footrests settle the rider for a short reach to narrow handlebars atop the yoke. This hot rod Lav eschewed such comforts in favour of a thin single-seat saddle with bump stop, rear-sets and those fabulous adjustable Jota bars that offer innumerable combinations of loft and lie that still manage to never quite be comfortable. Needless to say, I bought it immediately, unseen. On arrival, the first impressions were favourable. My new SF1 looked clean and tidy. Even better, it came with a huge box containing all the stock parts removed to make this period cafe racer, including footrests, dual seat, switches and indicators. Even the tyres were brand new, except they were decades old; Schrodinger's rubber, if you like. They were also oversized, one of my pet
hates and something I see all too often on old bikes. So big were they that the poor Laverda teetered precariously on its centrestand and looked in danger of falling over. I turned on the fuel and pressed the button, the mighty twin started. Before it had the chance to change its mind I jumped on and went for a quick ride. The carburation was anything but spot-on with terrible low speed response but sheez, was it quick! Emboldened by the power, I increased speed and the green monster immediately began to weave and shake its head; it had to be the tyres . Back at home, both shaken and stirred, I began to mentally compile the list. New tyres were ordered, Conti Go! I like the higher walls and rounded profile on these old bikes, they work well and have a sympathetically classical profile (as well as an exclamation mark). A pleasant few hours were spent tidying some of the wiring and the many weeks of lockdown just flew by as I attempted to find a comfortable set-up >-
No self-respecting Laverda twin can be expected to handle properly unless it's on the right rubber. Keywords: Conti Go! Apparently the Avons just didn't tagliare la senape, whatever that means
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OCTOBER 2020 I 9
RealClassic on the Jota bars; some things never change. I serviced the motor and found nothing untoward, everything was perfectly set and the erratic 36mm pumper Dell'Ortos were quickly beaten into submission. In fact, everything seemed perfect and the monster was ready for riding ... apart from one thing : the clutch.
~-il==~-.)
with an action more akin to a 125, yet the Italians felt the need to equip them with lifters so heavy that I needed two hands to operate them. This bike, with all the promised extra power, had a clutch that had been uprated to provide even more grip and so heavy was it that I couldn't really hold it in at a standstill! There is, as you might expect, a fix. The twins and triples can be modified by cutting a slot in the clutch cover and fitting an aftermarket extended clutch arm. This reduces effort at the lever by about a third. I looked down and to my horror saw that it had already been done. Oh. Re-routing the cable and careful adjustment has improved things a little, but it remains terrifyingly heavy and is certainly going to be investigated further over the winter. What's it like to ride? Well, fans of the twins (like me) generally prefer them to the more obviously glamourous triples. The SOHC 750, very loosely based on the Honda CB72 but with no fewer than FIVEmain bearings, is immensely strong, over-engineered and hangs off a similarly massive frame. Coupled with sturdy Ceriani forks and, in this instance,
10 I OCTOBER 2020
Koni shocks, the ride is firm and incredibly stable and encourages full use of the 70-plus available horses. It tracks through corners as if on rails and only the best of the Italian competition, a round-case Ducati, would be able to go quicker. Japanese and British offerings would flounder due to suspension and flex issues or simply be out-gunned by the Breganze bomber. Laverda's own triples are, in fact, slightly lighter and little more powerful than the top twin, but they .. . 'enjoy' that slightly odd sensation of the whole bike turning around the steering column and weight carried very high, making them far more difficult to ride quickly, at least for me. The lower, heavier 750 feels planted and the rider sits in, rather than on, the bike.
Surprisingly, despite all this engine work and unfiltered carburation , the SF1 remains whisper-quiet on its stock exhaust system with underslung balance pipe, usually very dented (it is) as befits the lowest point on a sporting motorcycle. With indicators removed and Lucas switchgear relegated to the spares box, there's little to distract the rider from the job in hand - hunting corners! All Laverdas should start instantly and th is is no exception. The five-speed close ratio gearbox remains a delight and only the heavy clutch detracts from the fun . Cruising at an
effortless 70mph there's no vibration to speak
engineered, reliable and fun,
of, but, as both needles begin to climb the exhaust takes on a hard edge and the tingles begin. The SF1flashes past the magic ton and runs comfortably beyond. There was
they remain a relative bargain. In the days of the ÂŁ 17k Laverda Jota and ÂŁ25k Ducati, the muscular SF can still be picked
very little back in 1973 that offered such a combination of poise and power, especially when the extraordinary reliability of the Laverda was factored in. The competition? From Japan, nothing came close. Britain? The T150 and Commando handled well, but lacked the power and
up for mere Norton Commando money. The owners' club and spares situation is very good, and to all intents and purposes it can be used and ridden like a modern motorcycle in that the SF rider can reasonably expect to get both there and back again in good order. Having foolishly sold the black 750 and lamented it ever Italian comfort is legendary. But just for one since, has the purchase of the green SF1, complete with tuned engine and boot. And no, that black one was quite some bike, after all. other upgrades, finally made up for that monumental error? Well, yes, the 'new' 750 is Falling in Lav again. What am I to do? I can't help it... Re at least as good as the old one and faster, to
regularly fell to pieces once moving. The main European competition, Moto Guzzi and BMW, were slow-turning shafties. Only the bevel twin Ducatis could really offer a challenge but, even back then, perfect preparation was paramount. One of the most complete motorcycles of the early 1970s, the Laverda 750 offers performance and poise, all rolled into a purposeful-looking package. Beautifully
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OCTOBER 2020 I 11
LET THERE BE LIGHT! My Yamaha XS had the standard 1980s headlight set-up, so I asked advice from the RCCrew w ho sent me to Paul Goff. I've installed some 21'' century tech and might be able to see where I'm going now! Michael Luff
TORQUE SENSE
There have been several comments recently about horsepower and torque. Torque develops in an engine due to the average or'brake mean effective ' pressure in the cylinder acting on the piston. This average force depends on piston diameter and acts on the crank throw, creating a torque at the crankshaft. The crankshaft torque is multiplied through the gearing of the primary drive, the gearbox ratio and the final drive ratio to become the torque at the rear wheel, minus the mechanical losses that occur at every stage. The rear wheel
12 I OCTOBER 2020
has an effective rolling radius and this determines the tractive effort or driving force between tyre and road. Tractive effort has to match a term known as Road Load in order to maintain speed or exceed it in order to accelerate. This all getting a bit heavy. What's Road Load?Well, this is the overall resistance to motion at a particular speed. It is made up from three main elements: Rolling resistance. This is usually considered as a fixed value based on a small percentage of bike and rider combined mass Gradient resistance. We can ignore this on a level road but it becomes very significant on hills Drag resistance. This is the one that really matters, especially at higher speeds. Drag resistance is calculated from several factors including the drag coefficient, frontal area, air density and vehicle speed. The crucial thing here is that as the speed increases the drag resistance increases exponentially , related to the speed squared Now the tractive effort at the speed we are travelling determines the power. Because of the exponential change in drag
resistance with change in speed, that is why the available engine power also needs to increase exponentially to increase the bike's speed. For example a typical small 100cc bike with, say, 10 horse power may be capable of 60mph, but to double that speed to reach 120mph it would need at least four times the power. In fact the bike would end up being heavier in any case,with more rolling resistance, so that is a conservative estimate and 50+ horsepower is more likely. Numbers and science, Isaac Newton, James Watt and friends. Fascinating. Mick Dobson, member 8716 Thanks for the technical explanation, Mick. I know I've recently infuriated several people by wilfully comparing horsepower and torque - 'apples and oranges: they holler. Of course they are correct, and each engine characteristic is entirely separate from the other . But there are times when I prefer apples to oranges! In motorcycling terms, that generally means that high -rev max imum power figures are of less interest to me than reaching the motor's torque plateau at lower revs. . . Rowena
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