BSA Bantam

BSA Bantam

Manufacturer	BSA
Production	1948–1971
Engine	2-stroke 125 cc (D1) 150 cc (D3) 175 cc (D5 Onwards)
Power	4.5 bhp (D1) 5.3 bhp (D3) 7.4 bhp (D5 & D7) 10 bhp (D10) 12.6 bhp (D14/4 & B175)
Transmission	Three speed gearbox (D1-D10) Four speed gearbox (D14/4-B175)
Fuel capacity	21.75 gal ("Teardrop" Tanks) 2 gal (D5 & D7) 1.9 gal (D7 Deluxe onwards)

The BSA Bantam is a two-stroke unit construction motorcycle that was produced by the Birmingham Small Arms Company (universally known as BSA) from 1948 (as a 125 cc) until 1971 (as a 175 cc). Exact production figures are unknown, but it was over 250,000 and some estimates place the number closer to half a million.

History

Despite the Bantam being considered the archtypal 'truly British' lightweight motorcycle outselling all others, it was in fact a German design, the DKW RT 125, received as war reparations. The same design went into production in at least two, and perhaps 4, other countries. Harley-Davidson started producing their Model 125 in late 1947 (several months before BSA) and the occupiers of East Germany, the U.S.S.R. began building the Москва (Moskva) M1A model even earlier, c.1946. In Poland the machine was made by MZ and Japan also produced copies.

The famous DKW RT 125 of 1950

The BSA designers converted the design to Imperial measurements for manufacture in Birmingham. This original Bantam, the D1, was released in October 1948 and continued in production for several years. It had telescopic forks, a rigid rear end, direct electrics, shovel front-mudguard and fishtail silencer, was available only in "mist green" and sold for £60 plus tax. Although the frame changed (first to plunger and swinging fork rear suspension), the engine remained a recognisable development of the original for the whole 23 years of production.

Engine

The engine is a unit construction (engine and gearbox of one piece) single cylinder 2 stroke. The barrel is cast iron while the head is alloy. The gearbox was initially three speeds, later versions went to four, fed through a "wet" clutch. Ignition was of two types a Lucas battery powered coil in earlier machines or a magneto by Wipac. The magneto was on a composite assembly sitting within the flywheel with its magnet inserts; windings gave power either directly to the lights (with a dry cell for when the engine was stopped) or through a rectifier into a lead acid battery. The early D1s had "fish tail" styled exhausts but this was replaced with the more conventional cylindrical silencer. High-level exhausts were made for the trials and off-road models.

Models

125 cc engine on a Bantam D1

Bantam D1 plunger frame suspension detail. The telescoping "cans" cover and protect the springs. Maximum travel is probably less than indicated by the amount of inner can (chrome) showing and the position of the chainguard. Note the rod-actuated rear brake.

This listing shows only the main variants and most models were available with refinements or in competition form. BSA had used a lettering system for their range of motorcycles and started the "D" series for their first two-stroke. The D175 was marketed as the B175 as BSA struggled against imports in the late 60s to its closure in 1972 (the larger capacity "B" series having helped make them the largest motorcycle manufacturer in the world). The engine size shown is nominal, British motorcycles were made 1 or 3 cc smaller than their tax bracket maximum to allow for re-bores and wear.

Model Name	Years Produced	Engine	Top Speed (mph)	No. of Gears	Rear Suspension	Electrics	Colour scheme
D1	1948–1950 1950–1953	125 cc, 4 bhp (3.0 kW)	45	3	Rigid Rigid and plunger	Wico-Pacy or Lucas	Mist-green only (including wheel-rims)
BD1		125 cc, 4 bhp (3.0 kW)	45	3		Wico-Pacy or Lucas	Limited edition, Black Tank with Chrome strips, leg guards & chrome wheels.
D3	1954–1957	150 cc, 5.3 bhp (4.0 kW)	50	3	Plunger (Swinging arm after 1956)	Wico-Pacy
D5	1958	175 cc, 7.4 bhp (5.5 kW)	57	3	Swinging Arm	Wico-Pacy
D7	1959–1966	175 cc, 7.4 bhp (5.5 kW)	57	3	Swinging Arm	Wipac
D10	1966–1967	175 cc, 10 bhp (7.5 kW)	57	3	Swinging Arm	Wipac with coil ignition and 60W alternator
D10 Sports & Bushman	1966–1967	175 cc, 10 bhp (7.5 kW)	57	4	Swinging Arm	Wipac with coil ignition and 60W alternator
D14/4	1968–1969	175 cc, 12.6 bhp (9.4 kW)	65	4	Swinging Arm	Wipac	Blue with two tone tank, painted above, chrome plate below.
D175/B175 & Bushman	1969-1971	175 cc, 12.6 bhp (9.4 kW)	65	4	Swinging Arm	Wipac

Pre-1958 (D1 to D5) had 19" wheels and 4.5" brakes. The 1959 D7 and later models had 18" wheels and 5" Brakes, Front and Rear. Describing the rear suspension as "Swinging Arm" is universal amongst English speakers, but every machine so described (and from every manufacturer, until the 1980s) would be better called swinging fork.

Developments and Models

Bantam D7

The D3 Major represented the first step in development of the Bantam, although the D1 would be produced for many years to come. A modern-style foam-filled pillion seat was fitted as standard, an economy and comfort breakthrough that had become popular as an option on the D1. It replaced the original standard fitting of a parcel carrier behind an individual sprung rubber seat.

The D175 (also known as B175) was a minor reworking of the D14/4. The spark plug sits in line with the cylinder head, front forks are stronger, slightly lower compression ratio at 9.5, separate headlight with high-beam warning, exposed rear shock springs, strengthened kickstart shaft, revised fixing on crankshaft compression disc plates.

Bushman

File:Risingwater.JPG

Bushman, note high exhaust.

The off-road Bushman version was available as an export model (for Australia in particular) but 300 were sold in the UK.

All UK Bushman models carry the engine number prefix BB.

See also

• List of BSA motorcycles

External links

• BSA Bantam D7 Restoration Page
• Mistgreen Bantam Website (Australian)
• Reference Library
• Bantam Racing (UK)
• Picture of The DKV