Thanks for the quick response, I understand that the Garmin Zumo 595LM motor cycle mount has a 3.5mm stereo line-out audio and a 3.5mm stereo line-in audio.
What I need to know is where the two leads hook into the BMW system?
I'm not sure that you can do what you are trying to do.
Did you get the BMW radio manual with your motorcycle?
If so there should be a section on connecting an iPod type device or USB device to the radio (you need the correct BMW adapter cable & it goes inside the radio compartment)