BSA Su­per Rocket

Old Bike Australasia - - CONTENTS -

BSA 650 twins came in such a var­ied ar­ray of mod­els that there is to­day, fifty four years af­ter the fi­nal pre-unit mod­els emerged from Small Heath, con­fu­sion as to which model was which. And for a com­pany as con­ser­va­tive as BSA, the ti­tle Road Rocket must have caused the Board much deep con­sid­er­a­tion, yet it was to prove to be the ul­ti­mate ex­am­ple of their pre-unit par­al­lel twin.

The lin­eage be­gan with the A7 of 1946, but had its roots pre-war in the pro­to­type 500cc over­head camshaft ver­ti­cal twin of 1938/39, which for ob­vi­ous rea­sons failed to progress for the next seven years. When it did, the en­gine fol­lowed the Tri­umph ex­am­ple, be­ing a pushrod de­sign that has been var­i­ously at­trib­uted to Val Page, Bert Hopwood, Her­bert Perkins and David Munro. Who­ever re­ally did most of the leg­work is im­ma­te­rial these days, but he or they did a fine job, be­cause the ba­sic lay­out penned in the late thir­ties stayed in pro­duc­tion for 17 years. Even when the pre-unit de­sign gave way to the new unit con­struc­tion A65 in 1963, the ba­sic en­gine spec­i­fi­ca­tion re­mained: a 360 de­gree twin with a sin­gle camshaft lo­cated at the rear of the crank­case op­er­at­ing the pushrods. The patented camshaft lay­out dis­tin­guished the BSA de­sign from its ri­vals, with Tri­umph, AJS/Match­less, Royal En­field and Ariel all opt­ing for twin camshafts, placed in front of and be­hind the cylin­ders. Nor­ton was the sole ex­cep­tion, but their sin­gle camshaft sat at the front of the en­gine. The 62mm x 82mm 495cc A7 also dif­fered from most in hav­ing the four-speed gear­box bolted to the crank­case, rather than housed in en­gine plates with means of ad­just­ment for the pri­mary chain. Three years of healthy A7 pro­duc­tion passed be­fore the in­evitable ca­pac­ity in­crease oc­curred in 1949, but although the 70mm x 84mm 646cc A10 looked very sim­i­lar to the A7, it was ac­tu­ally a com­pletely new de­sign. On the 650, the en­gine and gear­box were sep­a­rated, as on most of the op­po­si­tion. Fin­ished in a fetch­ing poly­chro­matic beige and chris­tened the Golden Flash, the A7’s big brother proved pop­u­lar from the out­set, although the US mar­ket was clam­our­ing for a sports ver­sion. This ap­peared in 1953 as the Su­per Flash, and the fol­low­ing year the home mar­ket got their own sporty twin, the A10RR Road Rocket, which also fea­tured the new swing­ing arm frame in place of the plunger chas­sis. Also new was a light al­loy cylin­der head, re­plac­ing the old iron item, but this re­tained the si­amesed in­let port that would take only a sin­gle car­bu­ret­tor – a fea­ture that re­mained un­til the end.

De­spite its evoca­tive ti­tle, BSA in­tended the Road Rocket to be a sports/tourer rather than an out-and­out per­for­mance ma­chine, but few cus­tomers saw it this way. The op­tional tachome­ter and TT car­bu­ret­tor ad­dressed the need for speed some­what un­til in 1957 the Road Rocket was qui­etly phased out and re­placed by what was ini­tially called the Su­per Road Rocket, which was quickly ab­bre­vi­ated to Su­per Rocket. With im­proved cylin­der head port­ing and a higher com­pres­sion ra­tio to make use of the slowly im­prov­ing fuel qual­ity, the A10SR also gained a stiff­ened crank­shaft. Gone too were the Ariel hubs used on the A10RR, re­placed with a new full width BSA de­sign front and rear. These were cast iron rather than al­loy with straight-pull spokes – 8 inch on the front and seven on the rear, with both brakes ca­ble op­er­ated. New less re­stric­tive and rather noisy si­lencers as­sisted in the quest for power. The new Su­per Rocket was to have been re­leased at the an­nual Earls Court Show in Novem­ber 1957, but when the show was can­celled it was left to BSA – and most other man­u­fac­tur­ers – to stage its own model re­leases. The A10SR poked out 43 bhp, de­spite a 1 3/16” Amal Monobloc car­bu­ret­tor be­ing used in­stead of the Road Rocket’s Amal TT9, which was avail­able as an op­tion. Spec­i­fi­ca­tions var­ied be­tween the UK and US mod­els, notably with re­gards to per­for­mance. For the 1959 model year, the US Su­per Rocket was avail­able in a Sap­phire Blue colour scheme, with big­ger valves in the cylin­der head, a slightly larger car­bu­ret­tor with in­let port en­larged to match. In­let valve size in­creased from 1.455” to 1 ½” and these en­gines were ex­ter­nally iden­ti­fied by a mod­i­fied tank trans­fer with ‘Big Valve’ splashed across the sym­bol­ised rocket leav­ing planet Earth. The ‘Big Valve’ en­gine be­came the stan­dard fit­ment from 1960. De­tail changes were made to the Su­per Rocket over the next four years, and in 1962 the fi­nal in­car­na­tion – the now highly revered Rocket Gold Star, ap­peared. The RGS was the re­sult of com­bin­ing the tuned 650 en­gine with a Gold Star type frame (with­out the kink in the lower frame tube to clear the sin­gle’s oil pump) and front forks, with a Si­amesed ex­haust sys­tem and a sin­gle si­lencer. Com­pres­sion was raised to 9.0:1 and power was up to 46 bhp. It was cat­a­logued with an ex­ten­sive list of op­tions and as an ob­vi­ous tilt to the Gold Star, the fuel tank was

sliver with red lines sur­round­ing chrome side pan­els. As it neared the end of its life, the Su­per Rocket also gained the 9.0:1 pis­tons and the camshaft from the US-spec Spit­fire, and the RGS Si­amesed ex­haust sys­tem was also avail­able as an op­tion, but in Au­gust 1963, the old twins were no more, re­placed by the new unit con­struc­tion A50 and A65.

A Da­ley ride

Our fea­tured BSA Su­per Rocket is owned by for­mer Aus­tralian Mo­tocross and Dirt Track Cham­pion Matt Da­ley from Bris­bane, who found the bike in Mel­bourne in 2015 with the help of his mate Barry Tay­lor. “It had ba­si­cally been built up around an en­gine that (BSA guru) Mike Reilly brought in from USA,” says Matt. “The owner sourced all the other parts and a lot of this – the frame, wheels and so on – came from Mike Reilly as well. Un­for­tu­nately I would have to say that the owner’s me­chan­i­cal skills were not all that great. I haven’t touched the en­gine but vir­tu­ally ev­ery­thing else I had to strip and re­build. I owned a Golden Flash in my younger days and I al­ways re­ally wanted an­other BSA twin, and I guess the Su­per Rocket is as good as you can get in the pre-unit con­struc­tion mod­els. This one had some worth­while mod­i­fi­ca­tions, such as the 12 volt electrics to re­place the 6 volt sys­tem. It had a new carb on it but from what I un­der­stand these Amal carbs can come from China, In­dia or Bri­tain, and this one just did not work, I could never get it to idle. So I bought a new Monobloc from Burlen Fuel Sup­plies in Eng­land and it is ab­so­lutely spot-on. The ig­ni­tion is fine too – I don’t ex­actly know who made the unit but the bike starts first kick, but I am plan­ning to fit a BTH Elec­tronic unit at some stage.

For­tu­nately Matt is an ex­pe­ri­enced en­gi­neer, but it took him two years to get the BSA to his sat­is­fac­tion. The brakes had been re­lined with too much shoe clear­ance and Matt had this rec­ti­fied by Rod Cook in Bris­bane. The brakes Matt now de­scribes as ‘ad­e­quate’. Far from be­ing a static ex­hibit or a show pony, this Rocket is rid­den reg­u­larly, and fairly briskly. “I reckon you could ride this (from Bris­bane) to Cairns no wor­ries,” he says. “It’s such a buzz to ride and it has the later type fi­bre­glass-lined straight through muf­flers so it had a won­der­ful ex­haust note. I fit­ted new Avon tyres which look right and work re­ally well, but it shows up the lim­its of the han­dling be­cause there’s not enough ground clear­ance and the side stand grounds eas­ily. I think it ac­tu­ally han­dles re­ally well and the sus­pen­sion is pretty good, but you no­tice the weight, it’s a heavy bike and even still has the lugs on the frame to fit a side­car. I have a new BMW R1200GS which is a great bike, but I en­joy the BSA so much, I wish I could ride it more. I feel sorry for the younger gen­er­a­tion who are miss­ing out on rid­ing some­thing like this.”

For­tu­nately Matt is an ex­pe­ri­enced en­gi­neer, but it took him two years to get the BSA to his sat­is­fac­tion.

New style BSA hubs re­placed the Ariel hubs on ear­lier mod­els.

Matt Da­ley with his Su­per Rocket.

TOP Twin in­stru­ments with 120mph speedo. LEFT Amal Monobloc carb with its ‘drip de­flec­tor’ to keep fuel away from the mag­neto. BE­LOW LEFT Mag­neto is Aus­tralian made. BE­LOW RIGHT 12 volt Alton gen­er­a­tor re­places the orig­i­nal Lu­cas unit.

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