In 2009, I did
some touring with another
Concours owner whose bike was
equipped with a GPS. The GPS benefits were pretty clear, not only for
North
American motorcycling but also for car use and bicycling in France.
Bought a used Garmin nüvi 270 via eBay, and a package of bits and
pieces from Hong Kong for mounting, including a heater vent mount. The
mount wasn't much good for the car, but with some sawing and filing,
seems fine for the Concours.
The chosen location is the dash above the left lockable pocket, which
corresponds to the clock location on the right. It provides a clear
field of view and is reasonably well isolated from engine
vibration. 
Stuck
the modified mount in place with 2 strips of 3M Acrylic Molding Tape. Funny stuff, doesn't
seem sticky to start, gradually bonds and
strengthens.
Bought a 2A power adaptor with
the right-angled mini-USB plug and pin-outs per
Garmin requirements (otherwise it won't run and charge at the same
time).
Unscrewed the connector end, removed fuse, unsoldered existing 12V
wires, soldered longer, slightly heavier stranded wires to the board
with motorcycle bullet
connectors on
the ends. With the fuse, spring and center connector gone, the
wires simply
come out the hole in the end. Connected the wires to fused switched 12V
power
under the left inner fairing.
Mounted
the power unit to the inside of the left fairing with sticky-back
velcro. Routed the 5V mini-USB output lead thru the opening in
the
fairing near the left mirror.
So mounting the GPS on the bike consists of connecting to the power
lead
and popping the cradle onto the ball mount.
Extra Twiddles:
Found and added Garmin vehicle icons for our blue Toyota Yaris,
a red Concours (actually a red MVAgustaF4
, couldn't find a Concours), a pedestrian and a bicycle. Also, the POIs for Logis de France hotels.
Results:
Installation
completed spring 2010. The
GPS is visible without blocking any of the dash instruments. To
overcome
engine and wind noise and earplugs I had to crank the GPS audio output
up to max. In
the rain, it gets removed to the tank bag. So far, no problems with
vibration.