In an earlier life, my favorite sound was the slap of my weekly copy of Motorcycle News hitting the doormat. I was 15, motorcycle crazy and loved watching motocross.
My new issue of MCN revealed the BSA range for 1966, which included two brand new scoots: the 441cc Victor Grand Prix scrambler, and the “dual-sport” Victor Enduro. I knew right then I had to own one. It took me another ten years, but I finally found a 1969 highway spec Victor Special. By that time, works rider Jeff Smith had taken two motocross world championships on the Victor Grand Prix.
BSA had entered the 1950s with new 500 and 650cc parallel twins. But their singles range was pretty much just pre-war models with fresh paint, and the engine and gearbox in separate cases. The C and B ranges of 250 and 350cc singles included three- and four-speed gearboxes, side and overhead valve engines, hardtail frames, and coil ignition with DC generators. Just about the only progress was the use of a telescopic front fork to replace the old girder units, plunger rear suspension, and an alternator to replace the dynamo. The final “pre-unit” 250, the C12 introduced swingarm rear suspension. But by any other standard, it was obsolete.
In 1951, BSA and Triumph had merged; and while the brands were still fiercely competitive (thanks in part to the personalities involved), there was some idea swapping. For its new unit construction 250, BSA had to look no further than Edward Turner’s Triumph Tiger Cub. The 200cc Cub itself was derived from the 150cc Triumph Terrier of 1953. Both employed unit construction with the crankshaft and gear train sharing the same cast alloy cases, split vertically left and right. Pretty much all BSA had to do to make a 250 was increase the bore and stroke from 63 by 64mm to 67 x 70mm – dimensions that were still in use a decade later in the Trident and Rocket 3.
1958 BSA C15
The C15 was a simple overhead valve design: The crankpin was a press-fit in the cast iron flywheels, with the crankshaft running on a timing side plain bushing, while the drive side main used a ball bearing. The connecting rod big end also ran on a plain bush. The camshaft was located above the crankshaft driven by skew gears, and activated pushrods that ran through a short external tunnel to the rockers. The drive side crankshaft carried a 50-watt Lucas alternator charging the six-volt battery without voltage regulation. Ignition was by coil.
A duplex primary chain drove the multiplate clutch and four-speed gearbox. The engine unit was held in a single downtube cradle frame with a bolted-on rear subframe carrying the swingarm and dual rear shocks, paired with a telescopic front fork.
And in its mild state of tune of a claimed 15hp, the C15 was reasonably reliable, though frequent oil changes were needed to prevent excessive wear in the rod big end and crankshaft bushing. The ignition distributor was also prone to coming loose (altering the ignition timing), and because of the unregulated charging system, riders were advised to ride with headlights on to avoid boiling the battery – though with just 50 watts from the alternator, that also risked running out of volts!
Trials (C15T) and motocross (C15S) competition versions of the 250 were produced with Lucas’s new Energy Transfer ignition system, and a tuned version of the 250 called the SS80 arrived in 1961. But also new to the U.K. market in 1961 was the Honda 250 Dream. And while it handily beat the C15 in most areas of technology, performance (with 24hp) and finish, it was also 100 pounds more expensive.
The C15 SS (Super Sport) 80 was a significant upgrade, with a claimed 20hp. A caged roller bearing replaced the big-end bushing (and was added to the base model C15 in 1966), the flywheels were forged instead of cast, and the gear ratios closer. And while it was faster than the plain-Jane model, that also exposed the weedy six-inch drum brakes inherited from the base model.
Introduced in 1960, a 350cc version joined the C15, with bore increased from 67 to 79mm. The B40 was identifiable by its cylinder barrel, which fully enclosed the pushrod tunnel. Upgrades included a wider rear brake drum and seven inch diameter drum front brake. In 1962, a caged roller bearing replaced the plain big end bushing, and many engine components were strengthened, including the front fork, and 18-inch wheels replacing the 250’s 17 inch items. Though 20 pounds heavier than the C15, the B40’s 20hp gave it a top speed of over 75mph. And because it was a stretched 250 rather than a small-bore 500, it was 100lbs lighter than the BSA “pre-unit” 350cc B31 that preceded it. The B40 also had a successful military career in the British forces. With the 350cc engine fitted into the C15T trials frame for extra ground clearance, the B40 remained in military service until replaced in the 1970s. The civilian B40 was dropped from the range in 1966, replaced in the lineup by the new Victor.
Why Unit Contruction?
From the early days of motorcycling, there were several good reasons why the engine, primary drive and gearbox were usually kept separate. Most manufacturers bought their gearboxes from specialist makers like Albion, Burman and Sturmey-Archer rather than make their own. Separate cases also made for easier primary drive adjustment and made for simpler castings – though there were three of them instead of one.
With unit construction of these three components, the drive train would be more rigid, allowing the unit to be used as a stressed member in the frame. Unit construction would typically make the drivetrain lighter and more compact, while also making it possible to use a gear-drive primary.
But a significant incentive for BSA was a decision by Lucas to end production of DC generators and Magnetos in favor of alternators, which, because they had no commutator or brushes, could run in primary oil. By 1963, almost all BSA and Triumph motorcycles were unit construction.
Victor
Meanwhile, at the BSA competition shop, work was progressing on an even bigger-capacity engine, initially of 420cc. Development finally settled on a capacity of 441cc. This was achieved by increasing the stroke by 20mm from 70mm to 90mm. Another round of strengthening components meant a needle-roller big end bearing, ball and roller bearing bottom end, and revisions in the gearbox, the layshaft now also running on needle roller bearings.
Although BSA had officially withdrawn from road racing, they were one of the leading teams in motocross, and the new 441cc scrambler was available to the works team for 1964. Jeff Smith rode the Victor (as it would be named) to two successive FIM 500cc World Motocross Championships in 1964 and 1965.
Chasing more power and less weight, the engine had grown to 494cc (83 x 93mm) and gained an oil-bearing Reynolds 531 steel tube frame. The final works-built Victor measured a full 498cc from 84 x 90mm dimensions while weighing just 224lbs! And while the Victor never won another world title, it carried “Big John” Banks to second place in both 1968 and 1969 championships. Street versions, the Victor Enduro of 1966, Victor Roadster of 1967 and B44 Shooting Star of 1968 were followed by the Victor Special for 1969-1970.
Meanwhile in the 250cc class, things were heating up. The 15hp C15 was replaced by the 25hp C25 Barracuda (B25 Starfire in the US) in 1967 with mechanical improvements and styling cues, including square cylinder barrels like the 441 Victor. Changes started at the crankshaft, this being forged in one piece with bolt-on flywheels. That meant a switch back to a split plain bearing big end. A new fully-welded frame replaced the bolt up item. To produce the higher power, compression was raised to 9.5:1, and the engine revved to 8,250rpm. In his book, BSA Gold Star and Other Singles, Roy Bacon writes about the new 250 having a similar top speed as the Victor, which “achieved it with a lot less hysteria and over-revving.” And if the 86mph was maintained for any length of time, the 250 motor was known to grenade…
Brakes finally got more serious, with the C25 getting a seven-inch twin leading shoe stopper, while the Victor Special added an eight-inch SLS. The 1970 range featured minor upgrades, clearing the way for a radical change.
Missing Link: 1963 BSA B40B
In 1962, a sports version of the B40, the SS90 joined the home market, claiming 24hp from increased compression at 8.75:1 – though actual top speed was around 82mpb, not the 90mph suggested by the name. The alternator output was increased to 60 watts.
In 1963, BSA imported a different version of the SS for the US market, known as the B40B Super Star. A larger Amal Monobloc of 1-1/8″ diameter replaced the 1-1/16″ on the base model, increasing output to a claimed 25hp. The B40B also copied the blade-style fenders from the SS and boasted a passenger grab rail. Otherwise, the styling was pretty much as the home-market B40SS, even retaining the increasingly dated-looking headlight nacelle.
Oil in Frame
The 1971 model line up included two 250cc bikes using essentially the B25 Starfire power unit in a new frame that carried engine oil in its single front downtube. The two versions were the B25SS “Gold Star” street bike (the name considered by many to be an affront to the memory of the original Goldie) and the B25T Trail. Components like the wheels, hubs, brakes, fenders, seat – in fact just about the whole bike except for the power unit – were new. Just as radical was the color, with all chassis painted parts finished in “dove grey,” not traditional gloss black. New Ceriani-style front forks were fitted, and the “conical hub” brakes were seven-inch rear and six-inch, (B25T and B50T) or eight inch (B25SS and B50SS) front.
Also new were three 500cc offerings. Based on experience with the B44, the engine was stretched to a full 500cc with 84mm bore and 90mm stroke. But while the new B50 shared the B44 stroke, the crankshaft was significantly strengthened with a larger crankpin, ball and roller bearings on the drive side, and a cast iron oil pump instead of alloy for more consistent oil pressure. Engine cases were strengthened and the primary drive beefed up. The B50 was available in three models: the B50T Victor Trail, the B50SS Gold Star 500 street and the B50MX scrambler – essentially a factory motocrosser making 38hp against the B50T and SS at 34hp. Chassis and cycle parts were essentially as the 250s, even down to the ineffective six-inch front brake.
Finally, BSA seemed to have gotten most of it right: The B50s were sturdy, torquey and powerful by standards of the time. But BSA was at the end of the line: the company was bust and the factory about to close. The last BSAs produced at Small Heath on April 14, 1972, were 11 Rocket 3s and seven B50SS Gold Stars.
Perhaps the most remarkable aspect of the unit singles range was how the tiny 150cc Terrier morphed into a 500cc thumper, more than tripling its capacity and horsepower. MC
Energy Transfer Ignition
Until the advent of Lithium-ion chemistry, batteries were as heavy as lead —  literally! In competition, reducing weight is an obsession, and a lead-acid battery could weigh ten pounds or more. But how to eliminate the battery?
Longtime supplier of ignition components to British bikemakers, Lucas designed a simple, and, what they hoped would be efficient ignition system called “Energy Transfer”, which was fitted to the C15T, C15S, B44GP, B50MX and Victor Enduro.
The idea was that the natural fluctuation of the output of a Lucas alternator could be used to generate a transient voltage at the ignition coil which would be triggered by a contact breaker, discharging through the spark plug. To achieve this, correct timing was critical: the contact breaker needed to open as the alternator output peaked. Too far from the peak and there would be no spark. There was no capacitor to store energy, like in a CD ignition system. And while trained technicians could make the system work, it was a challenge for shade-tree mechanics. More than one was heard to say they had no idea where the energy was transferred to, but it wasn’t the spark plug!
