A very competent friend assembled his BMW crankshaft on the (tiled) kitchen floor at some scarey temperature achieved in the oven. Apparently they go together perfectly easily at the right temperature. Impressive, to me at least.Quite a few motorcycle engines in the past have a crank like this, and the few competition two strokes are still built like this. Suzuki T500 twin and GT750 triple, and all BMW motorcycles before 1969 have this feature. There are no conrod bolts as they have closed ends and are assembled with the crank pieces using roller bearings.
Yes, it was a single, for a Farmobile restoration.I have only pressed together single cranks and have paid for my twins to be done. One BMW R60/2 twin crank that needed hard chroming, then surface grinding a bearing seat area, I sent to a BMW crank specialist in Alabama USA. Price was good, freight was pricey. All up total, balanced, fully rebuilt with all new bearings including freight $600, new crank $1200.
Much of BMW bike engine/gearbox assembly on the pre1969 Is done through heating one part to enlarge it slightly giving a light press fit for bearings.
I recall in my early apprentice days, that a colleague used to do up Honda Scamps, with a twin 360cc engine. He used to press the crank apart, I am assuming now to replace the roller bearings in the conrod bigend, as these must have been a weakness. When reassembling the crank there was lots of tapping with hammer to get the concentricity of the main bearings in axial alignment before final pressing together. Anyway he used to get them going again and sell onto people as first cars for their children. There was also a 600cc engine option as well. I suspect he got them for low cost as most people would not attempt to repair the engine with failed bearings.Quite a few motorcycle engines in the past have a crank like this, and the few competition two strokes are still built like this. Suzuki T500 twin and GT750 triple, and all BMW motorcycles before 1969 have this feature. There are no conrod bolts as they have closed ends and are assembled with the crank pieces using roller bearings.
Not relevant but.... I recall cruising a Gov't Holden in 1972 at 70 mph near Mount Gambier and being passed at high speed by a red Honda Scamp... That was the big engine one I always presumed....I recall in my early apprentice days, that a colleague used to do up Honda Scamps, with a twin 360cc engine. He used to press the crank apart, I am assuming now to replace the roller bearings in the conrod bigend, as these must have been a weakness. When reassembling the crank there was lots of tapping with hammer to get the concentricity of the main bearings in axial alignment before final pressing together. Anyway he used to get them going again and sell onto people as first cars for their children. There was also a 600cc engine option as well. I suspect he got them for low cost as most people would not attempt to repair the engine with failed bearings.
When you think about it, they were probably great for a town runabout, but a 360cc engine in a 550kg, 3Mt long small car is still quite small. But it worked and was accepted at the time - early 70's.