Sunbeam S7 and S8

Sunbeam S8

Manufacturer	Sunbeam Cycles Limited (Subsidiary of BSA)
Production	1949–1956
Engine	487 cc parallel twin OHC four stroke
Bore / stroke	70.0 mm × 63.5 mm (2.76 in × 2.50 in)
Power	24 bhp (18 kW) @ 6,000 rpm
Wheelbase	57-inch (1,400 mm)

The Sunbeam S7 and S8 are British motorcycles designed by Erling Poppe with styling loosely based on the BMW R75 designs that were acquired as war reparations by BSA (full rights to the Sunbeam brand had been acquired from AMC in 1943).^[1] Built in Redditch, the unusual engine layout was similar to that of a car. The engine was a longitudinally mounted inline vertical OHC 500 cc twin based on an experimental 1932 BSA design (the Line-Ahead-Twin - LAT) with coil ignition and wet sump lubrication which, through a dry clutch, drove a shaft drive to the rear wheel. The inline engine made this technologically feasible—horizontally-opposed ("flat") twin engines on BMW motorcycles had already used shaft drives following the system employed by the four cylinder Nimbus since 1918. The early S7 was expensive and over engineered, which is why it is now the most sought-after and commands a premium over the S7 De Luxe and the S8, which were produced with fewer features to reduce costs, while retaining many of the innovative parts of the early Sunbeam and updating some ideas.