BSA Bantam

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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	1.75 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 (ie BSA) from 1948 (as a 125 cc) until 1971 (as a 175 cc). Exact production figures are unknown, but it was over 250,000^{[citation needed]} and some estimates place the number closer to half a million.^{[citation needed]}

[edit] History

Despite the Bantam being considered the archtypal 'truly British' lightweight motorcycle^{[citation needed]} outselling all others, it was in fact a German design, the DKW RT 125, received as war reparations.^{[citation needed]} The same design went into production in at least two, and perhaps four, 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.^{[citation needed]} In East Germany the machine was made at the original DKW factory by IFA, which later became MZ^{[citation needed]} and Japan also produced copies.^{[citation needed]}

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 out of recognition (beginning with conversion to plunger and then swinging fork rear suspension), the engine remained a recognisable development of the original for the entire 23 years of production.

[edit] 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.

[edit] 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.

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.

[edit] Developments and Models

Bantam D7

[edit] D3 Major

The D3 Major represented the first step in development of the Bantam, although the D1 would be produced for many years to come.^{[citation needed]} First produced in late (most likely October was the first released) 1953 the D3 continued in production until 1957. 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.

In addition, the front suspension was made more substantial in volume and the cylinder was not simply bored out but was enlarged with distintive larger thermal cooling fins. These larger cooling fins was also added to the post-1953 D1's, albeit they maintained their smaller bore.

[edit] D175/B175

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 (as they are from the larger capacity C15, 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.

[edit] Bushman

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.

[edit] See also

• List of BSA motorcycles

[edit] External links

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