BSA Bantam – One clever little rooster

Bike Profile

OBA Issue 17
Old number one. The original D1 Bantam, with deeply-valanced front guard, green wheel rims and distinctive 'pancake' muffler.

Did everyone have a Bantam at some stage of their motorcycling experience? It would seem so – the ubiquitous green midgets were everywhere in the ‘50s – carrying mail, checking gas meters, shuffling backwards and forwards to work, and even racing.

There were many innocent victims of World War 2, among them the DKW factory in Zschopau. From the time of the Axis surrender in May 1945, it was a free-for-all amongst the liberation forces as they picked over the remains of Germany’s industry, offering prizes as ‘reparations’ to British companies. The Bristol concern received the 6-cylinder BMW design for the their cars, and DKW’s RT 125 engine, a humble but well-designed three-speed two stroke single of 123 cc capacity, was offered around, with, initially, little interest. A 125 two-stroke? I shouldn’t think so, old boy!

But the RT 125 was more than just another conventional two stroke. As far back as 1930, DKW had used the Schnuerle loop-scavenging process which eliminated the old deflector piston and greatly improved efficiency, and the company also did a great deal of work on their patented transfer port system. Several companies, notably Adler and TWN (Triumph Werke Nurnberg), managed to side-step the DKW patents with their own flat-top piston and transfer port arrangements.

As the post-war feasting on the DKW carcass continued, the RT 125 design found its way to Voskhod in the Soviet Union and to Poland, where WFM began producing a modified version. Across the Atlantic, the DKW design appeared in Harley-Davidson colours as the ST, or Hummer, which was progressively increased in capacity to 165 cc. Much later, Japan got in on the act too, with the appearance of the Yamaha YA-1.

Back in Blighty, there were still no takers until in early 1948, when BSA decided to accept the offer and announced the new D1 Bantam, resplendent in Mist Green, right down to the wheel rims. The BSA version was identical to the DKW, except that the entire motor was reversed in a mirror-image fashion. Bore and stroke were 52 mm x 58 mm, with full circle flywheels running on press-in shafts. A pressed in big end pin was used, with un-caged rollers 7x7mm diameter running directly on the connecting rod eye and pin. The two-ring piston was slightly domed, running in a cast iron barrel with an aluminium alloy cylinder head, giving a 6.5:1 compression ratio. A transfer port on each side of the barrel in line with the crankshaft was matched to recessed cast in the crankcase, with the barrel spigot cut away around the transfer ports. An oil collection recess was machined into the crankcase at the base of each transfer port, and from these oil-ways were drilled leading to the main bearing on the drive side and on the timing side. Carburation was via a 5/8” bore Amal. Sparks came from a Wico-Pacy (Wipac) flywheel magneto and generator mounted on the left crankshaft, with the rotor inboard of the stator. Primary transmission was on the right via a single-row chain, with the three-plate, six-spring clutch running on a bronze bush. Departing from the usual practice, the three-speed gearbox had the clutch on the right but the final drive sprocket on the opposite side, with a small pointer on the left crankcase to indicate which gear you were in – not that anyone really noticed. The shaft for the gear change ran through the centre of the kick start shaft, and contrary to usual British practice, changed in an up-for-up pattern.

OBA Issue 17
Left: Something to crow about indeed! An early advert for the BSA Bantams. Right: D1 engine showing the generator/magneto. Note the indicator for gear position.

Initially, only the engine was offered, and as an export-only item, but within months a complete machine was displayed to the press. Called the Bantam D1, the motorcycle featured a single loop tubular frame with rigid rear end and sprung, but un-damped telescopic front forks. A deeply-valanced front mudguard was attached to the top section of the forks, meaning that the wheel moved independently. The fork springs actually screwed onto the legs and were held in place by top nuts. The ends of the fork legs were flattened to take the front axle nuts, with a 4.5-inch front brake. 2.75 x 19 inch tyres were used front and rear. A distinctive feature of this model was the flat-sided ‘pancake’ muffler.

The 4 bhp Bantam had a top speed of just 45 mph (72 km/h) but returned excellent fuel consumption – around 120 miles per gallon – and at an initial UK price of £60 (plus another 16 quid for the dreaded Purchase Tax) the Bantam was an instant hit, not just in its home market, but worldwide. UK sales were further boosted when the Bantam (painted red) became the preferred choice for the Post Office deliveries.

Still carrying the D1 prefix, a plunger rear suspension frame was added in 1950, although the rigid continued to be catalogued at a slightly cheaper price. With the un-damped rear end came a new fully-valanced mudguard, and the centre stand gained a return spring to replace the original style held in place by a clip. Thus began the Bantam dynasty which had somewhat of a dual personality. One side a mild little commuter, and on the other, a machine that responded readily to the efforts of the expert two stroke tuner, and which almost single-handedly formed the grid for the Ultra Lightweight classes in road racing, scrambles and short circuit racing in Australasia for almost 20 years – but that will be the basis for a separate story.

What ever turns you on

Not everyone is besotted with Vincents, Manx Nortons, Bonnevilles or Gold Stars. For some, like the late Oliver Francis John ‘Ollie’ Reeves, it was the Bantam that took his fancy. He didn’t deliberately set out to create the world’s largest collection, but that’s possibly what transpired due to his efforts, and to those of his son, Philippe, or Phil to his friends. The result of the Reeves’ efforts is around 35 machines, from the first D1 to the last – the Aussie-aimed Bushman B175. Phil certainly knows his Bantams, and can intimately describe the model-by-model difference, foibles, and in some cases, faults. Here’s a run-down of the evolution of the species and how to tell them apart.

Bantam D1: First cab off the rank, and described in detail in the earlier text. The D1 had an aluminium headlight shell and rim, which meant it didn’t rust. But the dry cell battery in the unit for parking lights often leaked causing corrosion of the shell in this and latter models. Phil says this and other reasons are why original shells are very rare these days. The switch inside the unit was controlled by a cable from the handle bars. The headlight itself was held in place by a bracket mounted on the bottom fork yoke. The deep-sided front mudguard doubled (at least in England) as the front number plates, which were moulded into the unit. A Smiths 55-mph speedo was mounted in the top yoke. The cover for the centrally-mounted tool box had two screws holding it in place.

Bantam BD: Sitting between the D1 and the D2 is the little-known BD model, the rolling chassis of which was similar to the D1 plunger frame model. Motor-wise, the obvious difference is the top end, which sports a bigger barrel that was designed to accept a large bore to take the capacity to 150 cc on later models. Options included crash bars, chrome rims and leg shields. There were also a limited number released in black instead of the traditional green with cream tank panels.

OBA Issue 17
The rare DDL (left) with Lucas electrics from 1953, with the D2 of the same year.

Bantam DDL: According to Phil, this is the rarest model in the Bantam lineage, and was not imported to Australia. Produced only from 1953 to 1954, this machine used Lucas electrics, including the head and tail lights, which in Phil’s opinion were ‘vastly superior’. The Generator and battery operated on a half-wave charging system, which produced a smoother-running engine. The ignition switch and light switch was located on the headlight. The 53/54 model had a parking light located below in normal Lucas fashion.

Bantam D2: Produced from late 1953, the D2 used the plunger frame, with the front mudguard now in more conventional style, attached to the bottom of the forks. The tool box cover had a single, central screw fixing and there was a rear brake stop light. A new cylindrical muffler replaced the original ‘pancake’ style.

OBA Issue 17
D3, the first 150 cc model.

Bantam D3: Available in the UK in late 1954, the D3 was the first 150 cc Bantam, which also had the option of the new swinging arm frame and was known as the Major. Engine power was up to 5.3 bhp with a blistering 50 mph top speed. A Battleship grey and cream colour scheme was also a departure from Mist Green, and a dual seat replaced the sprung saddle on the swinging arm model and was an option on the plunger model. The basic shape of the cylindrical muffler introduced on the D2 was retained, but the muffler itself was tapered longer on the swinging arm model. The fuel filler cap moved from the left to the right side of the tank.

OBA Issue 17
The D5, featuring revised swinging arm frame and 175 cc engine.

Bantam D5: Yes, there was no D4 for some reason known only to BSA itself. Introduced in 1957, the D5 boosted capacity to 175 cc, producing 7.4 bhp and capable of 57 mph. A slightly revised swinging arm frame boasted improved geometry and better handling. The fuel tank was of larger capacity and a slightly different shape. Colour scheme was maroon with cream tank panels.

OBA Issue 17
Completely redesigned frame on the D7 with 18 inch wheels.

Bantam D7: Incorporating a completely new swinging arm frame, the D7 and D7 DL (De Luxe) introduced in 1964 was styled along the lines of the larger BSA twins, including the Nutley blue or Royal red colour décor. Wheels were now 18-inch. The D7 model also used a later version of the Wipac electrics. The DL had separate switches for the ignition and lights, with an extra coil for emergency use in the case of a flat battery.

OBA Issue 17
D7 Pastoral.

Bantam D7 Pastoral: With an eye on the emerging Australian agricultural market, the D7 Pastoral used hydraulically damped forks for the first time and a new swinging arm frame. These were also used on the road bikes. The bike in Phil’s collection was his father’s personal machine, and has been modified for road use by changing the gearing and the road type air cleaner and side covers fitted. Originally the Pastoral was fitted with a large capacity air filter.

Bantam D10 (plus Sports & Bushman): Similar to the D7, the D10 used Wipac coil ignition with a 60W alternator, and power increased to 10 bhp. The D10 gained an extra gear – the first 4-speed Bantam. This was also the first appearance of the Bushman model aimed at the Aussie market. The Bushman gained a higher ground clearance frame than the road versions, as well as stronger rear shock absorbers, and heavier forks sourced from the C15T.

OBA Issue 17
Bantam D14/4.

Bantam D14/4: By this time the writing was on the wall. The Japanese had started to take over the lightweight market and Bantam sales were seriously affected. The Bushman model was plagued with ignition problems from the Wipac energy-transfer system, to the point that Adelaide BSA agents Taylors sent back most of the models they received. The D14/4 was the fastest Bantam yet, with 12.6 bhp propelling the machine to 65 mph. Metallic blue was used for the tank with chrome bottom panels and a round plastic ‘Gold Star’ badge. The Bushman had Bushfire orange and white colours. All the D14/4 models had a larger exhaust pipe and muffler system and a heavier kick leaver with swivel top.

OBA Issue 17
B175 Bushman.

B175 (plus Sports & Bushman): The beginning of the end for the Bantam and B.S.A. itself. Produced from 1969-1973, The D14/4 powerplant was used except for the position of the spark plug, which was now vertically in line with the cylinder head. Ranged against the new wave of Japanese off-road and specialist Ag bikes, the Bushman sold like kittens.

Ignominious though the Bantam may be to many, Phil Reeves is passionate about the role the model played in motorcycle history. And there’s no doubting that without the Bantam, fewer motorcyclists would have got their start to two-wheeled freedom at all. As a collectable item, Phil says the bubble has well and truly burst. “When my father and I were collecting these bikes, $200 was the most we paid, and that was for the D7 which is a totally original, one-owner bike. Now, people pay thousands for them. And rightly so I believe they deserve their place in history as much if not more than some others.”

There’s no disputing that the Bantam, during its salad days, was the biggest-selling individual model in the world – achieved by its commercial acceptance for postie and other duties, and its role in providing cheap, reliable transport for commuters world wide. It also played a major role in helping BSA become, for a time, the world’s largest motorcycle manufacturer.

Story Jim Scaysbrook with technical assistance from Phil Reeves. • Photos: Sue Scaysbrook

OBA Issue 17
This article first appeared in Old Bike Australasia Issue No.17