BMW 1928 R57 494cc 2cyl ohv 3408

BMW 1928 R57 494 cc ohv transverse twin frame # 25723 Engine # 70343

The 1928 BMW range comprises four models: two in the 500 cc class, the R52 sv and the R57 ohv, and two models in the new 750 cc class, the R62 sv and R63 ohv. The new 494cc models are again further developed: the front brake diameter goes from 150 to 200 mm, and there’s a new 3-speed gearbox with oil lubrication instead of the earlier grease-filled boxes. The kick starter now works in line with the crankshaft, the earlier models are started with a kick backwards. The gear shift position has been lowered, it’s now closer to the engine. At this time the company has some 1500 employees and sales are going well. Setright remarks about the new models in “Bahnstormer, the story of BMW Motorcycles”: “”It was interesting that the ohv versions were no longer merely modifications of the side-valvers. Prior to the R52 all BMW motorcycles had a piston stroke of 68 mm, identical to the cylinder bore. But now it was recognized by their engineers that where power was sought (as in the ohv engines) a large piston area was desirable, and that were low-speed flexibility was sought (as in the side-valve engines) a low ratio of bore and stroke would be desirable. Thus the R52 and R62 both had crankshafts giving a stroke of 78 mm, the bores being 63 and 78 mm respectively; the sporting versions, the R57 and R63, maintained the old 68 mm stroke with bores of 68 and 83 mm.”
The R57 power output remains on the same level as that of the earlier R47, 18 hp @ 4,000 rpm. Development usually makes a machine heavier: The R57 tips the scales at 150 kg, 20 kg more than the R47. Notwithstanding the higher weight and equal power output, the company claims a 115 km/h top speed, 5 km/h more than the R47 reaches.

Our R57 has been painstakingly restored and comes with Bosch electrics and 160 km speedo. She’s been part of a private BMW collection and has been unused for years, so some checks will be advisable. Only 1006 R57 machines are built, so this is one of the rarest 1920s BMWs.