Under the right hand passenger grip is the radio. Near the radio (just forward of it) is the GPS input connector to the radio. See my video below for how I did my own GPS connection to this.
1) The Audio out jack from the Garmin harness is wired into the Spyers radio GPS input plug via a cable BRP provides.
2) 12V power comes from the Spyders GPS plug to the Garmin harness to provide power.
That is all that is connected to the Spyder. The other connectors on the Garmin harness are not used by the Spyder.
So you know the GPS input connector from the radio ONLY support mono audio input. This is the Spyder's radio limitation not the GPS. Thus when trying to play music from the GPS, it will be mono not stereo. Again see my video as I prove this fact. So getting a GPS with XM, MP3, whatever support, no matter what if the GPS is wired to the radio, it's MONO!
Yes, per the Spyder's radio design, any audio input to the GPS connector overrides anything the Spyder's radio is playing. You cannot change this unless you unhook the GPS from this connector!!!
If you have Bluetooth on your helmet you can bind the Zumo to your helmet and now get true stereo..... but also realize GPS audio directions overrides anything else the Bluetooth unit is playing!!! GPS has priority so your going to have the same issue.
My video may help you understand:
Bob