That was sadly modofied too late. We were having some fun on bumpy roads in Georgia, when my bike suddenly and inexplicably died. Over the next few days we were to find out, that the voltage rectifyer (VR) had overcharged and blown my relatively new battery!
Testing it the usual way (running the bike and reving while measuring the voltage at the battery terminals) had indicated the VR was fine, since the voltage stayed between the allowed 13-15V. But some googeling soon revealed, that the hotter the VR gets, the more volt it lets through. So when you just start the bike from cool, the readings will be fine. But hard riding on a very hot day will cause it to overheat!
This is partially to do with its positioning between the hot engine and the bash plate (which stops any cooling air flow). BMW have since recognised this and on the newer GS the VR is situated where the old ones just have a cover over the alternator and VR cable connectors on the right hand side of the engine.
So that’s where we repositioned the VR to. You can buy the relevant bracket for about $100. So we bodged it of course! Screw an aluminium plate into the cable-cover holes, bend it over the cables (connectors) and attach the VR to the plate. Et Voila! Now the airflow should cool the VR down. (You can also use two really long screws (if you can find them) attaching both the VR and the bracket at the same time, as the holes in the VR match those in the engine.)
We’ve not ridden in quite as hot conditions, but almost, and on the same difficult road. I had a multimeter connected, and it showed the charge as staying within range 🙂