Rebuilding a BMW R80 Airhead Transmission
Seven years ago I dragged this 1978 BMW R80 out of a basement in Massachusetts. I immediately found out it had badly rusted cylinders and the pistons were frozen. I didn’t document what happened next, but the top end got completely rebuilt. The cylinders were sent out to be serviced and to accept R90 pistons, upping the compression to 10.5, and the displacement to 900cc. The motor purred like a kitten and ran beautifully. However, about 50 miles later the transmission failed and the bike had to be towed home. Since then the bike has been sitting on a lift with the transmission spread out on a bench.
The time had finally come to get this old girl back on the road. Let’s build a transmission!