1925 BMW R39
Engine
Engine type Air-cooled, 4-stroke, single cylinder vertical
Bore x Stroke 68.0 x 68.0 mm (2.67 x 2.67 inches)
Displacement 247 cc
Valves OHV
Compression ratio 6.0:1
Max Power 6.5 hp @ 4000 rpm
Max Torque
Fuel system 1 carburettor Type BMW Spezial 20 mm
Transmission 3-speed
Final drive Cardan
Clutch Single plate dry clutch
Ignition type Bosch magneto generator type G 1.8V/15W
Starting system Kick starter
Lubrication Lubrication by gear pump in sump
Exhaust
Spark plug Bosch W 175
Battery 6 volt 12 amp hour
Gear ratios
Dimensions
Frame type Twin loop tubular frame
Castor
Overall length 2050 mm (80.70 inches)
Overall width 800 mm (31.49 inches)
Overall height 950 mm (37.40 inches)
Wheelbase 1380 mm (54.33 inches)
Seat height 785 mm
Ground clearance 185 mm (7.3 inches)
Dry weight 110 kg
Fuel capacity 10 litres
Colors
Suspension (front) Plate spring, 4 laminae
Suspension (rear) Rigid
Tyre (front) 27 x 3.5 balloon or with 26 x 3 high pressure tyres
Tyre (rear) 27 x 3.5 balloon or with 26 x 3 high pressure tyres
Brake (front) Internal shoe drum brake 150 mm / 5.90 in diameter
Brake (rear) External shoe brake at the gearing on Cardan shaft