Take five! Heyday of the 500cc parallel twin
Pete Kelly compares a quintet of popular 500cc parallel twins from the 1950s.
Considering Britain’s road and traffic conditions of the 1950s, with not a motorway in sight until the short Preston bypass was opened on December 5, 1958, a smooth-running, overhead-valve 500cc parallel twin was everything a dedicated solo rider or sidecar enthusiast could wish for – and, for those who could afford them, were a very popular choice at the time. Setting the standard for such machines for decades to come, the Triumph 5T Speed Twin, complete with girder front fork and solid rear end, was launched at the 1937 Motorcycle Show but sadly the Second World War intervened on the infamous night of November 4, 1940, when the Luftwaffe’s blitz on Coventry wiped out the Triumph factory and virtually everything in it. It wasn’t until 1946 that work on the model could be resumed at Meriden, when the Speed Twin was offered with a telescopic front fork and a choice of sprung-hub or solid rear ends. Development steadily continued until, by 1955, the 5T finally embraced a modern swinging arm. A road test on that model in the May 5, 1955, issue of The Motor Cycle reminded me so much of the phraseology used by those old-fashioned test scribes. Kickstarting a bike into life, for instance, always entailed a complex ‘drill’ – something that must seem pretty quaint to modern motorcyclists who just push a button and they’re away! Another point noted in all parallel twins tests was vibration (something that possibly grew worse as the American appetite for ‘cubes’ led to larger capacities), with the road test scribes working out exactly at which speed and in which gear it occurred, and from where it could most be felt on the machines. The Speed Twin report began: “First in the field of four-stroke, vertical-twin five-hundreds in 1937, the 5T has kept abreast of modern trends since that time. Two years ago, replacement of the separate dynamo and magneto by an alternating current generator and coil ignition marked the inception of a widespread change in British motorcycling engineering practice” (although this wasn’t welcomed with open arms by many enthusiasts at the time). “The adoption of pivoted-fork rear-wheel suspension with hydraulically-damped spring units ensures a markedly higher standard of rider comfort, with spring adjustment for various loads, and the model has a much sleeker look than its sprung-hub-rear predecessors, with a restyled oil tank, matching box on the left for the battery and tool kit, and longer and wider dual seat.” That writer of 65 years ago found the 1955 5T a gentlemanly machine to ride; comfortable, tractable and quiet, with light handling, a lively engine performance and good fuel economy. His description of the 7-inch diameter drum brakes front and rear as being ‘powerful’ was not borne out by the officially recorded stopping distance of 35ft from 30mph, at a time when 29ft or 30ft might have been more up to the mark. With a highest one-way speed of 86mph, the Speed Twin was no slouch, but at the other end of the scale, once the engine was thoroughly warm it was happy to pull at 30mph in fourth gear, including climbing some of London’s steepest hills with an all-up 24-stone load, without any tendency to ‘pink’ (the usual term for pre-ignition). No wonder the traffic cops loved them! The Speed Twin fired up at the first or second jab on the kick-starter whether the engine was hot or cold provided that, in the latter case, the Amal Monobloc carburettor was flooded liberally and the air-lever closed. An emergency ignition position was fitted for discharged battery conditions, but this required much more welly on the kick- starter. The clutch was light and took up the drive firmly, but slipped a little during repeated full-bore quartermile standing starts. Perhaps better times might have been achieved with a fraction less enthusiasm off the line!
Reporting on the oil-tightness or otherwise was another ‘must’ for road testers, and, in the 5T’s case, while the upper half of the engine remained clean, a film of oil appeared on the right-hand side of the crankcase and gearbox shell. During long, fast runs, a smear of oil leaked from the gearbox or chaincase onto the back of the rider’s left overboot, while slight seepage from the oil tank filler cap soiled the inside of his right trouser leg. By the end of the test, both exhaust pipes had blued for a few inches from the port ends. The phrase ‘damning with faint praise’ invariably applied to headlight performance, and in the Speed Twin’s case, this went: “Illumination provided by the headlamp main beam was satisfactory for speeds of up to 70mph on many roads after dark, but the pool of light thrown onto the road by the dipped beam was concentrated on too small an area.” Performance-wise, mean maximum speeds were 45mph in first ; 64mph in second; 77mph in third and 84mph in top. Petrol consumption was 97mpg at 30mph, 80mpg at 40mph, 78mpg at 50mph and 64mpg at 60mph. The fuel tank held four gallons. In the spring of 1955, the Triumph Speed Twin, finished handsomely in Amaranth red, cost £217 4s including the dreaded UK purchase tax. Another popular 1950s 500cc parallel twin was the 497cc BSA Shooting Star, which the 16 December 1954 issue of The Motor Cycle described as: “A zestful, exhilarating sports mount with superb steering and braking, yet notable for its tractable engine and smooth transmission.” The Shooting Star was the third in line of parallel twin 500s marketed by the famous Small Heath factory since 1946 and quickly became one of the most popular machines of its kind. The test writer enthused: “Basically a 1949 Star Twin with modifications including a light-alloy cylinder head and the latest BSA pivoted-fork rear springing, the Shooting Star combines tractability, excellent traffic manners and relatively low fuel consumption with an open-road potential in the best traditions of the modern sporting five-hundred. Ease of handling, sweet transmission and smooth low-speed pulling make it delightful to ride in traffic, while zestful acceleration in all gears, a tireless engine and superb braking and steering cater admirably for the rider who wants something out of the ordinary in 500cc performance.” The long manual ignition control lever allowed accurate settings to be achieved, and the machine’s lowish overall gearing saw it to operate sweetly and unobtrusively at 30mph in its 5.28 to 1 top gear, with smooth acceleration even from that speed, and neither ‘pinking’ nor transmission snatch. Premium-grade petrol was used throughout the test, and the rider wrote: “Retarding the ignition to the minimum allowed a non-snatch speed of 13mph in top gear, while in dense city traffic, the Shooting Star was ridden frequently in first gear with the clutch fully engaged and the ignition completely retarded at a pace so slow (approximately 5mph) that the speedometer wasn’t even registering.” Given its head on the open road, the BSA could cover long distances with the speedo registering 80 to 85mph with the rider normally seated, and its top speed of 91mph, obtained against a vicious cross-wind, might well have been bettered. The engine showed no sign of tiredness, and there was no discolouration of the exhaust pipes throughout the test. Engine vibration was virtually non-existent below 70mph in top gear, but, above that, a slight tremor was felt through the petrol tank and handlebar. However, when the engine was revved to the point of valve-float in bottom and second gears, vibration become pronounced through the footrests. No offence was given by the Shooting Star’s exhaust, for at all engine speeds and throttle openings the note remained pleasant in tone and reasonably unobtrusive, with mechanical noise confined to slight piston-slap and valve-gear murmur, and although some leakage occurred from the primary chain case and oil tank, the power unit remained virtually oiltight in spite of very hard driving. Starting was a first kick affair whether the unit was hot or cold. With a cold engine, the best drill was to retard the ignition half-way, close the air lever and just lightly flood the carburettor. As soon as the engine fired, the air lever could be opened half way, then fully after a few hundred yards. For warm engine starts, partially retarding the ignition would prevent kick-back. On full retard, the tick-over was so slow that individual power strokes could be counted.
An accessible fingeroperated throttle stop on the Amal Monobloc carburettor permitted the tick-over to be set in an instant, and another notable attribute of the new carburettor was its instantaneous response to snap throttle openings. The gearbox and clutch matched the high standard of the engine. From a slow idle, engagement of bottom gear from neutral was noiseless, and a leisurely pedal movement ensured clean upward changes, while downward changes could be executed as rapidly as desired. There was no difficulty in selecting neutral from bottom or second gears, and the clutch was smooth yet firm in taking up the drive, and freed perfectly. The Shooting Star inspires confidence as soon as the rider straddles it,” wrote the tester. “The riding position is first class, and long runs can be completed without fatigue. Relative positioning of handlebar, seat and footrests results in a pleasant distribution of the rider’s weight, and the tank width between the thighs is comfortable. "Steering and stability are both of a high order, and while a steering damper is fitted, it was used only when obtaining maximum speed figures under the difficult conditions prevailing. At low or high speeds, the machine could be heeled over stylishly, when it would follow a chosen line accurately, and no lowspeed heaviness was perceptible.” An increase in spring poundage over earlier models gave the suspension a notable degree of firmness at low and medium speeds, which, on long runs, brought to light a slight hardness in the upholstery of the dual seat, but neither pitching nor bottoming was experienced. Both brakes were powerful and reasonably light to operate, and on wet roads the rider felt no qualms about applying them as hard as was considered safe. For once, even night riding was safe and pleasant, with a main headlamp beam allowing the machine’s performance to be used generously on main roads. The road tester concluded: “Appearance of the Shooting Star is in keeping with its all-round performance. It is a machine calculated to inspire pride of ownership.” Performance figures were amazingly similar to those of the Triumph Speed Twin, with maximum speeds through the gears at 43mph in bottom, 63mph in second, 88mph in third, and, in prevailing conditions, 90mph in top. The 8-inch diameter front and 7-inch diameter rear brakes gave an excellent stopping distance from 30mph of 29ft, and fuel economy worked out at 100mpg at 30mph, 85mpg at 40mph, 75mpg at 50mph and 65mpg at 60mph. In December 1954 the Shooting Star, with its distinctive metallic light green paintwork, chrome tank panels and polished light-alloy parts cost £231 12s including purchase tax.
After wondering why I could find no road tests for the 498cc Matchless G9 parallel twin in the Mortons Motorcycle Archive, I realised this was because Associated Motor Cycles refused to supply road-test machines at the time – a great pity because this 85mph sports mount adopted a full swinging arm rear end while its rivals were still using sprung-hub or plunger back ends. The machine caused a sensation when it was unveiled at the 1948 Earls Court Motorcycle Show, but because in those days the emphasis was on ‘export or die,’ it took until the late summer of 1949 before the first British customers managed to buy examples. The G9 is close to my heart. During my early days of motorcycling, Dad bought a secondhand one attached to a Watsonian child/adult sidecar for ferrying my mother and sister Joan around in. So memorable was a family holiday at the Isle of Man TT in 1963 that, as a ‘retirement’ present to myself in 2009, I commissioned a canvas painting of a scene from that glorious fortnight, featuring both the outfit and my own 150cc Excelsior Universal which, better still, became the subject of a Gibson’s jigsaw puzzle entitled ‘Holiday Hold-Ups.’ At the crack of dawn, Dad would ferry my brother and me from our bungalow holiday home at Laxey to Creg-ny-Baa to watch the early morning practising. As 1963 was the year when ‘Scuderia Duke’ brought the Gilera fours out of mothballs for the first time since the end of 1957, it was well worth waiting in the earlymorning chill with a flask of piping hot coffee to hand, to see them competing against MV Agusta’s ‘fire engines’ once again. What I remember most about the G9 was its short, deep dual seat, the absolute racket from its stubby megaphone-styled ‘silencers’ (made all the worse by echoing off the right-hand side of the sidecar), the distinct vibration from the 66 x 72.8mm bore and stroke engine, the feeling of low grunt rather than searing acceleration when getting away from rest, and the Teledraulic front fork and ‘Jampot’-sprung rear – but we loved it to bits! Its meaty-looking engine (and, of course, that of its AJS equivalent, the Model 20) was noted for its three-bearing crankshaft, but the extra rigidity brought about by the bearing between the two disc flywheels tended to redistribute the vibes to the rest of the bike. Excessive pressure from the twin oil pumps could also lead to blown gaskets between the cylinder barrels and crankcase and liberal coatings of leaked oil. Dad eventually swapped the outfit for a 650cc BSA A10 with a monstrous Busmar sidecar that must have made Mum feel like the Queen in her coronation coach. One wet and slippery Sunday afternoon, brother Geoff and I were following him down a steep, winding hill from Dugdale’s Motorcycles at Alvanley, Cheshire, when he hit a lethal combination of cow muck and wet leaves that spun the outfit round until he was facing us going backwards, clutch lever in as he wondered what to do next, and mother banging on the Perspex side windows in panic. We almost fell off laughing! The only G9 price reference I could find was for a 1953 exportspec Super Clubman – £248 10s 6d including purchase tax. Another iconic 500cc overhead-valve parallel twin from the 1950s was the coil-ignition 497cc Norton Dominator 88, and a test report in the 10 April 1958 issue of Motor Cycling noted its fast and untiring performance combined with exemplary roadholding from its full-cradle ‘Featherbed’ frame and ‘Roadholder’ telescopic front fork. “The steering is a delight, and the handling a bendswinger’s dream,” wrote the lucky scribe allotted the task. “Time and time again during the 2,100 test miles, fast open-road corners were tacked with a zest that would not have arisen on a mount lacking this quality. Even chronic bumps failed to cause deflection from the intended line, and complementary to the cornering was the Norton’s sure straight-ahead handling.
“Bottom gear was frequently held to 30mph, second to 65 and top sent home at an indicated 75, although these figures could all be exceeded by 10mph, with a maximum topgear speed of 90mph.” Even under hard acceleration, the gears went home so easily and freely that he sometimes wondered whether the pinions had moved at all. “The cruising speed could be anything up to full bore, with the only sign of stress being a failure of the condenser which, housed in the distributor cover and retained by a spring clip, was easily replaceable. "Apart from a single inoffensive period of vibration, corresponding to 38mph in top, the engine was pleasantly smooth. Petrol consumption averaged 66mpg, and oil was used at the rate of 600 miles per pint, a curious conundrum as none seemed to be burnt, and no oil leaked from the engine other than breather mist over the underside of the crankcase.” The stopping power of the brakes from speed was better than the 30ft from 30mph achieved on dry tarmac might suggest, and it was possible to lock either wheel on a dry road. The Lucas equipment fitted to 1958 Norton twins now took the form of an AC crankshaft generator with a full-wave rectifier, which gave sufficient output to feed a 7-inch block lens light unit which threw a good beam up the road and to each side, permitting a safe cruising speed of 65mph on open roads. Once again, in the event of a flat battery, an emergency starting position was installed, and though it called for vigorous cranking when cold, it did work. When the charged battery was in circuit, warm engine starts required nothing more than switching on and simply depressing the kick-starter once! The tester concluded: “The 1958 Norton Dominator 88 is one of the most exhilarating road-burners to pass through my hands in a very long time.” Finished in polychromatic grey enamel, with lots of chromium plating, including the tank panels, and many buffed and polished light-alloy parts, the ‘88’ was a good looker, too. The full-width, light-alloy front hub housed an 8-inch brake, with a 7-inch brake at the rear. Fuel consumption was 94mpg at 30mph, 87mpg at 40mph and 75mpg at 50mph, and in April 1958 the Norton Dominator 88 cost £283 16s 2d including purchase tax. Royal Enfield’s handsome, compact and sprightly 496cc Meteor Minor de Luxe boasted many features in the established Redditch tradition, including separate iron cylinder barrels with heavily-finned lightalloy cylinder heads, a one-piece cast iron crankshaft, a half-gallon oil compartment formed integrally with the crankcase, a four-speed Albion gearbox bolted to the rear of the crankcase, a vane-type cush drive in the rear hub and a transmission shock absorber in the clutch centre. A road test in the June 26, 1958, issue of The Motor Cycle revealed it to be the fastest of the quintet, when a strong following wind boosted the highest one-way speed to 97mph. The relatively low seat height of 29½ inches afforded by the Meteor’s smaller 17-inch diameter wheels was a boon to those below average height, for feet could be placed firmly on the ground at traffic halts, The test rider observed: “Though pleasantly light, steering was very positive and enhanced the feeling of confidence already engendered by the low seat and comfortable riding posture, although for speeds over 60mph a footrest setting 3in further back would have been preferred. At both ends of the speed scale, it was easy to pick a precise path without conscious effort, and riding the Meteor Minor to a standstill feet-up was child’s play. "Stability on greasy surfaces was also of a very high order, and only on fast bends with undulating surfaces was there a tendency for the model to weave as the rear suspension pitched. The generous steering lock allowed a turning circle of just 15ft, and braking from the 7in drums front and rear was first class at all speeds. “When the road surface permitted, the model could be pinned down firmly, with both tyres squealing, either from a traffic crawl or from top speed, and several hours of riding in teeming rain failed to impair brake efficiency. “Smooth running and unusually supple transmission allowed top gear to be used at 30mph, and the effectiveness of the two rubberblock transmission shock absorbers was emphasised by the minimum non-snatch speed of just 13mph in that gear. “On the open road the engine undertook any amount of hard work without tiring, with half-throttle giving an indicated speed of about 75mph. At speeds of up to 60-65mph in top gear there was a pleasing absence of vibration. At 70mph, engine vibes were perceptible but not objectionable, but from 75mph upwards, they could be felt through the dual seat. “Mechanical noise was average, and the siamesed exhaust was unobtrusive. There was oil discharge from the crankcase breather pipe during hard riding, and oil also fouled the distributor cover and the region of the left pillion footrest.” The new clutch was light to operate, took up the drive smoothly and was free from drag, but a slight tendency for the friction plates to stick sometimes resulted in bottom gear engagement to be accompanied by a slight jerk. Repeated clutch slipping, as when riding for several miles in heavy traffic or making a succession of rapid starts for the quarter-mile acceleration figures, brought about a slight increase in control backlash, which returned to normal when the clutch cooled. Upward gear changes could be made quickly and cleanly without special precautions, but engagement of the cogs could be felt when changing down. Neutral could be selected easily with the gear pedal, but in any event the gearbox was fitted with the familiar Royal Enfield neutral finder which permits ready selection of neutral from any gear except bottom. As for the lights: “The intensity and spread of the headlamp beam were adequate for night riding at normal speeds, but with the lamp unit deflected to its lowest setting, the dipped beam was parallel to the road surface.” The scribe found the prop stand commendably safe for parking, while the centre stand gave firm support, close to the point of balance. The ready detachability of the tank after removal of only one bolt was greatly appreciated when checking the valve gear, and primary chain adjustment was checked through an aperture in the chaincase. Finish of the Meteor de Luxe was black for the frame and fork, with a choice of polychromatic burgundy, Wedgwood blue or black for the mudguards, rear chaincase, tool and battery boxes and petrol tank, which had chromium-plated side panels. Mean maximum speeds were 35mph in first; 55mph in second; 79mph in third and 89mph in top, with that amazing highest oneway speed of 97mph with a strong following wind. Fuel consumption worked out at 85mpg at 30mph, 82mpg at 40mph, 75mpg at 50mph and 58mpg at 60mph, and in June 1958 the Meteor Minor de Luxe cost £274 9s including purchase tax.
8830R and, in addition, it also has TT stamped on the crankcase. As far as he knows, it was last on the road in 1932; Joe has owned the Rover since 1963 and has kept it just as it is. Joe adds that if he can be of help to Gilbert Bredimus (the owner of last month’s Rover), then we will be happy to put them in touch. But Trevor Stansfield believes that the Rover was a 1915 model as the exhaust pipe sweeps back under the engine – for 1916, the exhaust silencer was in front of the engine. He also thinks that it’s a TT model, something that is supported by the engine number. As the Rover in OBM428 has had rear footrests fitted, Trevor suggests that it had passenger footrests added later in its life. He also adds that it’s a lovely find and we have to agree. Pete Blick has just finished this cracking little Royal Enfield (Pic.11 and Pic.12) and has taken the opportunity to put his own mark on it. Having bought it as an unfinished project, he’s welded on new brackets so he could use a BSA tank, rebuilt the engine and made a rack. The rear light and numberplate are from a Triumph Tiger Cub and, with new chromed wheels, we can see this is going to be a lot of fun. Pete is now rebuilding another Crusader, this time in standard trim although he says he has quite a few missing parts to track down. We look forward to seeing the end result of that rebuild too!