5 Occbsadbd34 Gold Star and 500Cc Velocette Venom Thruxton Mick Duckworth
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5 OccBSADBD34 Gold Star and 500cc Velocette Venom Thruxton Mick Duckworth OME British motorcycles have be- When the factory produced a hot new Venom. They were entered by dealer teams come more like holy icons than motor 500cc sportster with an all-alloy engine in in the annuallong-distance race for show- vehicles. They are cherished, polished 1937, a BMRC Gold Star award for a room models at the Thruxton eircuit. S and revered. But not used much. 100mph lap at Brooklands made a fitting Goldie exponent Eddie Dow fielded Vipcrs BSA's Gold Star and the Velocette launch. And provided a model name that in the event, but the most influential Velo Verrom Thruxton are typical of machines could be used on a line ofhigh-performance protagonists were Reg Orpin and Geoff that get put in this category. As the arche- singles up to the early sixties. Dodkin. typal 500cc sporting singles of the fifties The Gold Star gave BSA a tremendous American tuners had been busy, too, and sixties, they have star status in the run of sporting success in postwar years. tweaking off-road Velocette singles expor- classic galaxy. They are also relatively Even in road racing, an activity Small ted since the forties. The fastest stateside rare, which makes them very expensive. Heath shied away from after disasters in machine was that entered in track events And they are fickle beasts, demanding the 1920s, it proved a winner. It was sold in by Los Angeles dealer Lou Braneh. Its sympathetic handling. 350cc B32 and 500cc B34 versions, which secret was a special cylinder head with a Consequently, many examples probably evolved in to the definitive, most sought- massive 2in-diameterinlet valve. wouldn't get as far as the nearest corner after Goldie, the 500cc DBD34 firsf made Clubman versions of the Viper and shop without causing trouble and exas- in 1956. Venom became available in the fifties, but peration. They don't do the mileage a The 85 x 88mm B34 pushrod engine had eventually US experience, and Orpin's machine needs to stay in good fettle. been tuned alm ost to the pitch of an over- enthusiasm for a cireuit-racing Velocette, This can make life difficult for press head camshaft racer. A lot of credit for the had its effect on the factory, resulting. in testers. Even when running ex am ples are 500's output of 40bhp at 7000rpm goes to low-volume production of the Venom found, they may be eosmetically excellent Roland Pike, developmentengineer at BSA Thruxton. Based on Orpin's 1964 500ee but disastrously unreliable. Or, justifi- from 1952 to 1957. And unlike his counter- Thruxton winner with a big-valve head, it ably, an owner may not want someone else parts working on AJS, Matchless and was on sale from mid-1965. riding their pride and joy, Which is why Classic Bike was lucky to find these two examples of single minded- Equipment ness. The Gold Star, a 1958 DBD34 model, belongs to John Simmons of Ipswich. A Both singles only As limited-production machines aimed al long-time BSA enthusiast and member of committed sporting riders, both singles the BSA Gold Star Owners Club, John only ever claimed to provide speed anti. acquired his Goldie three years aga and euer claimed to roadholding. Owners ean treat any other lost no time in restoring it to a superb state attributes they discover as bonus points. of originality. He enjoys group riding, prooide speed In each case, apre-war engine design even though his nearest clubmates live 50 has been the subject of gradual develop miles away. On a fine weekend he typic- and roadholding ment. Although its manufacture ceased ally covers 250 miles. before the Thruxton's appearance, the Neal Barry, a member of the Velocette Gold Star unit is more modern in its all- Owners Club from Bracknell, provided the alloy eonstruction and its higher-revving' Thruxton, a 1965 model. He has owned it Norton projects, he worked under the con- capability. for twelve years, and keeps it in slightly straint of having to make the Gold Star Both engines have a built-up crankshaf non-standard trim with a British Racing acceptable for ACU Clubmans racing, and roller-bearing big-end. The Velo's Green eolour scheme and single seat. But, which demanded an almost road-Iegal crank and its casing are narrow enough tl1 having raced Velos in the past for special- specification. put the primary drivechain inboard of'the ist tuner Geoff Dodkin, he has, appropri- The Gold Star was made during prosper- final transmission line. The crank in thE ately, made his maehine into a replica of ous years at BSA. But Velocette's Venom test Goldie was found to have a crack one ofthe singles entered in raees success- was one of the final products to come from across most of one flywheel when restored fully by the southwest London dealer in the Hall Green factory before closure in probably due to non-standard lightenin the sixties. He regularly rides it on the 1971. The 86 x 86mm 499ce single was the work carried out in the past. It now runs road as weil as parading the Thruxton at ultimate development ofthe M-series push- with a newly-made component from Brit CRMC race meetings. As it came from the rod engine designed by Charles Udall and ain's Gold Star Service. factory, the Thruxton was finished in either first used in the 1933 250cc MOV model. Design contrasts in the valve gear affec blue and silver, or black. Although the company built a sporting maintenance procedures. The Thruxton reputation on the strength of its pre-war has hairpin valve springs and no tappet ohc K-series machines, it opted to focus on gap between its pivoted cam followers ane History the utility market in the postwar period. rockers. This means removing the timing But when the lightweight 200cc LE water- cover to adjust clearances. On the Gole The giant Birmingham Small Arms com- cooled flat twin flopped, the pushrod Star, gaps are set by rotating the rocket pany spotted a major trend in the motor- single was revived. spindIes in eccentric housings. The BSA cyele market in the mid-thirties. The sports Possibly influenced by BSA's success has two separate camshafts, while tht and recreation machine was supplanting with the Gold Star, Velocette introduced Velocette has two lobes on one shaft. Bot] the go-to-work utility bike that BSA had sports versions of their road 350 and 500ec use trains of gears to drive cams, mag specialised in. singles in the mid-fifties: the Viper and netos, oil pumps and rev-counters. 26 Classic BikE ROADTEST .ve maintenance is often a feature This involves slipping the elutch, which set up it can cause trouble, but the test : en . es meant mainly for competition, is liable to respond by overheating and machine's worked nicely, though opera- - -' eowners ofthesemachines both say refusing to free. Its draggirig prornotes tion was a little heavier t.han on the BSA. a they find little tinkering is necessary stalling and the owner's ride becomes a A notable feature of the Velo gearbox is a oncethey had mastered basic adjustments. misery - especially if kick starting is un- kickstarter mechanism that only prornotes Crirical amongst these is carburation, but reliable, as it often is. minimal rotation of the crankshaft with the Amal GP racing type fitted in each To John Simmons' credit, this Gold Star each swing. ca e does ha ve the virtue of simplicity . No was particularly well-behaved. He can In keeping with the Thruxton's gener- time need be wasted on tick-over settings, start it readily - a novice needs a little ally outmoded specification it was built for which the GP has no provision. practice - and despite the RRT2 box and a with a pressed-steel primary drive enclo- Both singles have distinctive exhaust sure: the Gold Star acquired an alloy systems. The Velocette's fishtail had a casing in 1952. camp, archaie look by the sixties, but it Gold Star The Velocette's frameis elearly an adap- had to be fairly efficient to permit speeds tion of an earlier rigid type. Its excellent of 129mph - a figure recorded by the FOR: instant power, glamorous handling has always been a source of Thruxton-based machine which won the style, slickgearchange wonderment to those who notice how little 1967500ccProduction TT. AGAINST: awkward bottom visible support there is for the swinging Its swept-back front pipe mimics the arm pivot, Hanger plates for the Thruxton Gold Star: as tyres improved the normal gear, brakes only adequate, rearset footrests may appear to add style of header pipe robbed machines of anti-social noise bracing, butin reality this is unlikely. cornering elearance. The BSA's stocky An all-welded duplex frame was one of PMn pipe terminates in one of the best Thruxton several major contributions made to Gold known components ever made for a motor- Star development by Bill Nicholson, cyele, the Gold Star sileneer. In fact, silen- FOR: responsive handling, BSA's star off-road rider of the postwar cer is not an accurate term, as BSA never effectioe brakes, flexibility period. Like Norton's Featherbed it fixes elaimed it to be road legal. A megaphone AGAINST: cramped the extreme ends ofthe swinging arm pivot made to look like a road muffler, it boosted firmly in gusset plates. the machine's power while satisfying the accommodation, tricky The Velocette can elaim to have more rules ofClubmans and production racing.