If you're talking about the motorcycle lead, rather than a butchered car power lead; There should be a fly-lead with a jack up near the plug that attaches to the GPS, This is for the Audio out.
EDIT: Just looked back a page, it looks like a butchered car cable with the cigar lighter/speaker hacked off, you can still see the strain relief grommet on the end.
I'm pretty sure that the black and red are power, best to search the web for a m/c power lead installation sheet and hope that the colours are the same. Would look it up for you and provide a link but that's quite a task on a mobile...
If the above is correct then, yes, the other two will be mono audio for directions. However, it's quite likely that you will get GLI (Ground Loop Interference) to with two audio devices (GPS & Autocom) powered from the bike. Best bet is to try connecting the power lead to the same source as the Autocom.
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