I also noticed the detents at 0º and 90º, and I knew they were functional. I thought they had a special tool to turn it, but apparently I'm wrong. The manual doesn't mention anything about an electric shut-off vs vacuum diaphragm as in all bikes. I remember seeing a vacuum line for the diapraghm valve, but didn't follow it to see if it went to an electric device. It must have one of the two shut-off devices. The only problem seems to be when removing the fuel tank.