BSA Bantam
The BSA Bantam was a lightweight 125cc 2-stroke single that was in production from 1948 through the 1971 model year. It was a huge seller for BSA with nearly 500,000 sold over its 24 lifespan. The Bantam is actually a German design produced by DKW as the RT125 prior to and during World War 2, supplying bikes to the German Army. At the end of the war, the Allies received, as war reparations from Germany, the rights to the design, and it spawned copies all over the world. The Soviets (officially still an Ally) actually got the DKW factory which was now in East Germany which continued production (it took until 1949 to rebuild the plant and restart production), and the USSR built a factory in Moscow in 1946 and began production there of the Moskva M1A, their version of the DKW RT125. In American, Harley-Davidson launched it as the Model 125 in 1947. In Britain, BSA got into the act in 1948 with the launch of the BSA Bantam. Even the Japanese got something out of the deal, but it took until 1955 when Yamaha built its first production motorcycle, the YA-1, based on the DKW design.
BSA built the Bantam in its Redditch plant, and they did something truly unique and clever. The DKW design placed the kick starter and the all-important foot-operated shifter on the left side of the engine. But as anyone familiar with British bikes knows, those things are supposed to reside on the right side, as God intended. So BSA did a complete mirror-image redesign to get those things on the right, as every British rider would expect. And, per British custom at the time, the conversion also changed the measuring system over from metric to inches (we call that ‘American’). The first iteration of the BSA Bantam, the D1 launched in 1948 in Britain’s export markets first, then in 1949 in the British home market. After the war, Britain’s economy was in a shambles and the government made exports of British goods a priority, to bring in some much-needed cash. So, the rest of the world got the BSA Bantam before the Brits did.
This 1948 BSA Bantam is a first-year D1 with rigid frame, big clunky fixed front fender, and 'fishtail' muffler.
The BSA Bantam D1 came with a 3-speed gearbox in unit with the engine (an early example of unit-construction). They came with a simple telescopic front fork and a rigid frame (no rear suspension). The front fender was mounted to the upper (stationary) fork legs and so didn’t move with the front wheel, so the fender need to be deeply valanced to give the wheel room to move. It was an awkward-looking solution, but the BSA Bantam was never intended to be a pretty bike. It was simple, cheap and utilitarian. That’s why the Soviets liked them. The ‘fishtail’ muffler was perhaps one of the few concessions made in the name of style. In fact, at launch the BSA Bantam came in only one color, Mist Green, with an ivory painted panel on each side of the tank. The early D1 Bantams didn’t even have a battery, relying instead on ‘direct electrics’. The lights only worked with the engine was running. A battery came later.
This 1949 BSA Bantam D1 engine has all the early features, like the smaller-finned top end and this flywheel cover.
It was the mission of the BSA Bantam to fill the desperately-needed role of cheap, basic transport to legions of cash-strapped Britons who needed a way to get back and forth to work. Early Bantams were priced at just £60 (about $100 USD), which seems crazy-cheap today.
The BSA Bantam engine evolved with the bike. The D1s displaced 123cc, the D3s bumped that up to 148cc, and from D5 onwards the Bantam had 173cc of displacement. All variants used a cast iron cylinder barrel and a cast alloy head. All BSA Bantam variants from 1948 t0 1968 model year had 3-speed gearboxes. A 4-speed gearbox was adopted in 1968 that ran through its final year of production in 1971. All models had a wet clutch. Ignition was via a Lucas coil system initially, which changed on later models to a Wipac magneto, incorporated into the engine’s flywheel. Its windings also provided power for lights. Early models used a dry cell battery while later units had a lead-acid battery and a rectifier. Early BSA Bantam D1s used a ‘fishtail’-style muffler that was very stylish but oh so hard to clean. And 2-strokes back then often needed cleaning from all the built up soot and burned oil in the exhaust. The fishtail was soon replaced by a conventional cylindrical silencer that had removable innards for ease of cleaning. Off-road models got a high side exhaust and magneto ignition with no accommodation for lights.
This 1968 BSA Bantam D14/4 engine shows later features like contoured engine covers and larger fins on the iron barrels and alloy head.
The ongoing development of and steady improvement to the BSA Bantam prompted several different ‘series’ that were improved enough to be differentiated from each other. Below is a breakdown of the BSA Bantam by series:
BSA Bantam D1 - 1948-63
123cc, 4 horsepower / 3-speed, 45 mph top speed
The BSA Bantam D1 came initially in 1948 with a rigid frame. BSA offered a plunger rear suspension as an option starting in 1950, and eliminated the rigid frame altogether by 1956. The D1 was offered with two different electrical systems. The Wipac system was available in two flavors, a 6-volt AC system with direct lighting (meaning the lights only worked when the engine was running), and a conventional DC system with a lead-acid battery. To make the AC system legal there had to be a way to keep the ‘pilot’ light (we Yanks call them ‘running lights’) when parked, so a dry cell battery (essentially a flashlight battery) was provided. However, it wasn’t rechargeable and so became disposable with it ran out of juice. A new dual seat became optional in 1953 and a second paint color, maroon, was offered for the first time in 1958 as an alternative to mist green. Also in 1958 the 100,000th BSA Bantam was built. It was a D1.
This 1948 BSA Bantam D1 shows the rigid frame and huge stationary front fender, a fixture of the Bantam until 1954.
BSA Bantam BD1 - 1949-53
123cc, 4 horsepower / 3-speed, 45 mph top speed
The BSA Bantam D1 came initially in 1948 with a rigid frame. BSA offered a plunger rear suspension as an option starting in 1950, and eliminated the rigid frame altogether by 1956. The D1 was offered with two different electrical systems. The Wipac system was available in two flavors, a 6-volt AC system with direct lighting (meaning the lights only worked when the engine was running), and a conventional DC system with a lead-acid battery. To make the AC system legal there had to be a way to keep the ‘pilot’ light (we Yanks call them ‘running lights’) when parked, so a dry cell battery (essentially a flashlight battery) was provided. However, it wasn’t rechargeable and so became disposable with it ran out of juice. A new dual seat became optional in 1953 and a second paint color, maroon, was offered for the first time in 1958 as an alternative to mist green. Also in 1958 the 100,000th BSA Bantam was built. It was a D1.
BSA Bantam D3 - 1954-57
148cc, 5.3 horsepower / 3-speed, 50 mph top speed
The D3 Major was introduced in 1954 and was the first major improvement on the original BSA Bantam D1. By increasing the bore from 52mm to 58mm the engine grew to a whopping 148cc producing an earthshaking 5.3 hp over the smaller 123cc engine’s 4.5 hp. Big stuff! The cooling fins on the top end were enlarged to improve cooling and it changed the overall look of the engine dramatically. Since this model overlapped D1 production, the D1 also benefitted from the improved top end. The D3 got a standard dual seat and a shallower front fender which now moved up and down with the front wheel. All early D3s had the plunger rear suspension, but this was upgraded to swing arm rear suspension in 1957. All D3s were painted gray with ivory side panels.
BSA Bantam D5 - 1958
173cc, 7.4 horsepower / 3-speed, 57 mph top speed
The D5 Super, introduced in 1959, had a larger 173cc engine now making a thunderous 7.4 hp, still based on the D1 architecture. This was accomplished with yet another bore job, this time to 61.5mm. A new polished alloy engine cover was added to the left side covering the Wipac “Geni-Mag” and streamlining the looks of the engine so that both sides nearly matched. Launched after BSA’s introduction of swing arm rear suspension to the BSA Bantam line in 1956 all D5s have it. The D5 also got an Amal Monobloc carburetor and a larger, more rounded fuel tank. All D5s are finished in maroon paint with ivory side panels.
This 1952 BSA Bantam shows the plunger rear suspension, optional starting in 1950 and replaced by swing arm rear suspension in 1956.
BSA Bantam D7 - 1959-66
173cc, 7.4 horsepower / 3-speed, 57 mph top speed
The D7 Super was similar to the D5 Super with a few changes meant to improve the breed. A new swing arm frame was developed, different than that used with the D3 and D5, and a new hydraulically dampened from fork was used, which was a shortened version of the forks used on the Triumph Tiger Cub. Starting in 1961 the ‘BSA’ tank badges changed to match BSA’s 4-stroke line of singles. Until then there are two color options offered: Royal Red and Black. But Sapphire Blue was added in 1961. A new tank arrived in 1965 along with another new color, Flamboyant Red. Coil ignition was added also in 1965 and in 1966 BSA introduced a new economy version (like the BSA Bantam wasn’t already economy enough) called the “Silver Bantam”, which was trimmed in sapphire blue with silver side panels.
BSA Bantam D10 - 1967
173cc, 10 horsepower / 3-speed, 57 mph top speed
BSA introduced the D10 in 1967 with more power than ever before. While still using the same 173cc engine as the D5 and D7, an increase in compression to 8.65:1 increased its power output to a mighty 10 hp. Even with this, the top speed of 57 mph didn’t change. The Amal Concentric carburetor was used on all D10s as was the electrical system with a new Wipac alternator. Points were moved from the left side of the engine to the right. The D10 was offered in four different versions, the Sports, Supreme, Silver and Bushman. The Sports versions were the first BSA Bantams to gain a 4-speed gearbox.
1968 BSA Bantam D14/4 'Silver'.
BSA Bantam D10 Sports - 1967
173cc, 10 horsepower / 4-speed, 57 mph top speed
Chrome fenders, a fly-screen and a bum stop (bump on the back of the seat) were added to the standard D10. The D10 Sports was the first BSA Bantam to have a 4-speed gearbox.
BSA Bantam D10 Bushman - 1967
173cc, 10 horsepower / 4-speed, 57 mph top speed
The Bushman was the off-road version of the BSA Bantam. It came with a high exhaust running along the right side, 19-inch wheels, a skid plate under the engine, increased ground clearance and a 58-tooth rear sprocket. All Bushman’s were painted in orange and cream.
BSA Bantam D14/4 Supreme - 1968-69
173cc, 12.6 horsepower / 4-speed, 65 mph top speed
The D14/4, all models, benefitted from another bump in compression, this time to 10:1 to increase horsepower output to 12.6 and the top speed to 65 mph.
BSA Bantam D14/4 Sports - 1968-69
173cc, 12.6 horsepower / 4-speed, 65 mph top speed
Got heavier front forks plucked from the BSA C12 line.
BSA Bantam D14/4 Bushman - 1968-69
173cc, 12.6 horsepower / 4-speed, 65 mph top speed
Got heavier front forks plucked from the BSA C12 line.
1969 BSA Bantam D14/4 Bushman with high exhaust, knobby enduro tires and extra ground clearance.
BSA Bantam D175 / B175 - 1969-71
The final installment in the BSA Bantam lineage, the D175, later called B175, was considered the best Bantam ever, in terms of power, handling and comfort. The top end cooling fins were revised again and the spark plug was now centrally located and vertical. This improved the combustion chamber shape and allowed BSA to lower the compression ratio slightly, to 9.5:1 without losing any horsepower. This made the engine smoother and more reliable. The front fork was upgraded again, this time to that of the Triumph T20 SH Sports Cub. The D175 had exposed springs front and rear. The final models, produced from 1969 to 1971 were finished in metallic red, blue or non-metallic black, all with white painted panels on the sides of the tank.
The end of the BSA Bantam in 1971 coincided nicely with the end of BSA in 1972. Unfortunately, changing times, more than anything else, overtook BSA as it did the entire British motorcycle industry, as well as the British car industry. Britain’s industries were still caught up in their glorious past, and refused to consider the alternatives, such as modernizing like the Japanese had done. In 1960, Edward Turner, the legendary creator of the Ariel Square Four and the Triumph Speed Twin (the first vertical twin) and now chairman at Triumph, traveled to Japan to ‘spy on the competition’. He returned confident that Britain still led the world in manufacturing chops and that the Japanese were backward and primitive and decades from ever building a motorcycle that Westerners would buy. Boy was he wrong! Within a few short years Honda alone was building more motorcycles in a single month than the entire British motorcycle industry was building in a year. How can you fight a force like that? The short answer is that BSA couldn’t, and so closed its door in 1972, leaving Triumph, which they owned in Norton’s hands. The rest is history. Today BSA is still in business producing optical equipment, rifle scopes and air rifles. In 2016, Indian tractor giant Mahindra bought the rights to the BSA motorcycle brand and are now producing new BSAs in India.
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