BMW R32

Make Model	BMW R 32
Year	1923 - 26
Engine	Four stroke, two cylinder horizontally opposed Boxer, pushrod operated 2 valves per cylinder.
Capacity	494 cc / 30.1 cu in.
Bore x Stroke	68 x 68 mm
Compression Ratio	5.0:1
Cooling System	Air cooled
Induction	1 x Special ∅22 mm carburetor
Ignition	Bosch high voltage magneto ignition
Starting	Kick
Clutch	Single plate, dry
Max Power	6.3 kW / 8.5 hp @ 3200 rpm
Transmission	3 Speed
Final Drive	Shaft
Gear Ratio	1st 2.27 / 2nd 1.50 / 3rd 1.08:1
Frame	Twin loop steel tubular frame
Front Suspension	Twin cantilever spring
Rear Suspension	Rigid, spring loaded saddle
Front Brakes	∅150mm Drum
Rear Brakes	Block brake
Front Tyre	26 x 3.5 low pressure or 26 x 3.5 high pressure
Rear Tyre	26 x 3.5 low pressure or 26 x 3.5 high pressure
Wet-Weight	122 kg / 268 lbs
Fuel Capacity	14 liters / 3.6 US gal

The flat-twin engine was common in 1920s motorcycles and many manufacturers around the world used the power unit in the fore-and-aft position. The Bavarian Motor Works at Munich introduced its M2 B15 flat-twin engine in 1922. These were supplied to Victoria and other manufacturers; BMW also used the engine in the Helios motorcycle. The following year, designer Max Friz produced a remarkable new design for a completely integrated motorcycle. The R32 was launched at the 1923 Paris Show. The side-valve 494cc engine was turned through 90° so that its cylinder projected into the cooling air. A three-speed car-type gearbox and clutch were bolted to the back of the engine. This layout had been used earlier on the British ABC machine (see p. 10). But unlike ABC, BMW chose to use shaft drive to the rear wheel. It has retained this engine layout and transmission system ever since, proving the worth of the original design.

The engine and gearbox unit of the R32 were put into a duplex tubular frame. Front suspension was provided by a leaf-sprung trailing-link fork. The use of shaft drive precluded the provision of rear suspension but it did allow the rear wheel to be removed without disturbing the transmission. The front brake was a drum while a dummy rim brake was added at the rear. The advanced specification included a centre stand, enclosed valve gear, automatic lubrication, and electric lighting. The valanced mudguards, raised fronts to the footboards, and the absence of an oil chain made the BMW an exceptionally clean and practical machine, especially for routine maintenance.

BMW R 32