Steve, Aiden:
Congratulations on getting the 2650s. That exact GPSR (the 2650) will always be my all-time favourite from all the Garmin GPSRs that I have ever owned. The 26xx series was the last series to have an "engineering-driven" user interface (as opposed to the current "Your Mom can use it out of the box, without reading the manual" interface), and best of all, the 2650 will perform dead reckoning if you take the time to hook up a speedsensor to the motorcycle.
There are two inputs needed for dead reckoning - one is an input from a speedsensor, and the other is an input that tells the GPSR if the vehicle is moving forward or moving backward. For motorcycle purposes, if you have an electronic speedometer, you can just tap into the signal sent from the transmission, or rear wheel, or wherever the speedometer gets its signal, and use that. As for the 'forward-reverse' issue, on automobiles this is normally achieved by tapping into the reversing light (back-up light) to tell the GPSR when the vehicle is in reverse gear. Unless you ride a Gold Wing, you won't have such a light, but what works equally well - what I did on my ST1100 - was to tap into the 'side-stand down' annunciator light, and set things up so that if the side-stand was deployed, the GPSR assumed the motorcycle was being moved backwards. This makes sense, because if I am going to paddle the thing backwards in a parking lot, I normally have the side-stand out.
Although Garmin strictly forbids it, you can tap into the ABS speedsensor mechanism to get a speed pulse. If you choose to do this, don't tap in physically (in other words, don't cut any wires), instead, find a way to pick up on the pulses being sent by one of the ABS speedsensors without cutting into the system. I'm not an electronics whiz, so I can't tell you how to do this.
Once the GPSR has the speedsensor input, it will instantly (and I do mean instantly - within half a second) switch into DR mode if reception of the satellite constellation has been lost. This works exceptionally well in tunnels, when riding along valleys, through urban canyons, and so forth.
Regards,
Michael
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