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BSA Motorcycles

The 5.57 h.p. Model.

This model has been for many years past a popular type of dual-purpose machine, because of its economy, power, simplicity, and reliability. For the motorcyclist who prefers the simplicity and economy of the large single-cylinder engine, and at the same time requires a machine for hard pulling and capable of taking heavy passenger loads, this model has all the necessary characteristics.

Engine.
Single cylinder, 5.57 h.p., 85 mm. x 98 mm. bore and stroke (557 c.c.). Roller big-end bearing, mainshaft mounted on large ball bearings. Aluminium alloy piston of special design. Silent timing gear, large capacity silencer, giving quiet exhaust without loss of efficiency.

Carburettor and Ignition.
Amac carburettor. Special carburettor fitted with air cleaner can be fitted as an extra. Magneto driven by adjustable chain in aluminium dustproof case.

Lubrication.
Gravity feed to mechanical pump of improved type, then to sight feed on timing case, and feeding to crankcase. A hand pump is also fitted for emergency use. Oil supplied to primary chain by depressing spring by-pass valve on sight feed. Hubs, fork links, etc., are fitted with grease-gun nipples.

Transmission.
Front chain, ½ in. x .305 in. Rear chain, 5/8 in. x 3/8 in. Front drive totally enclosed in two-part chain case, and rear drive protected by an efficient guard. A camfaced cush drive fitted to engine shaft. For gear ratios, see page 69.[1]

Clutch and Gear-box.
Clutch contained in large chain wheel. Floating dry-plate type. Controlled by lever on left handlebar, with large diameter cable. Gear-box is B.S.A. three-speed. All gears constantly in mesh and increased in width to give additional strength. The kick-starter mechanism is enclosed in gear-box. The change-speed lever is on right side of tank. Screw adjustment of box position for accurately setting chain tension.

Frame.
Suitable for sidecar work, with integral sidecar lugs. Head fitted with B.S.A. steering damper. Weldless steel tubing and forged steel lugs are used throughout. Head lug of continuous type giving great strength. Strong carrier is fitted.

Spring Fork and Handlebar.
B.S.A. type spring fork, fitted with barrel spring and shock absorbers. The handlebar is adjustable, mounted behind steering head, with forward bend at centre and back sweep at ends. Longer rubber grips. Touring type bar if specified.

Tank.
Tapered type supported by brackets brazed on to the frame. Filler caps, unleakable, secured with bayonet joint and chain. Combined priming cock and petrol tap. Capacity: petrol, 17/8 gals., oil, 3 pints.

Wheels and Tyres.
Wheels: heavy gauge rims, 19 in. X 2½ in., enamelled taper roller bearings to both hubs. The tyres are Dunlop cord, 26 in. x 3.25 in., wired-on, or 27 in. x 4 in. wired-on balloon tyres with special front mudguard can be fitted as an extra.

Brakes.
Both internal expanding type, 7 in. diameter. Front operated by lever on right handlebar, rear by heel pedal on independent fulcrum on right side of machine. Grease-gun nipples fitted to cam spindles..

Saddle.
Terry spring seat, De Luxe type. Brooks supple seat B.190/2, if specified.

Mudguards.
Rear, strong and 7 in. wide, of plain section. Front, fitted with side wings of ample dimensions.

Footboards.
Large footboards or footrests to order.

Notes

1. More pages from this book are available at Craig Howell's Flickr pages. Craig Howell

Source: Book of the BSA by Waysider. Pitmans, 1928.