If your speedo is working, but not your odo, it could just be that the gears are stripped in the odometer (not unusual).If you're not afraid to get in there and take things apart, you can buy a replacement from MAXBMW for about $110. Part number 62 11 2 305 175http://www.maxbmwmotorcycles.com/fiche/NotesParts/62112305175_1_B.jpg
Bulb grease and dielectric grease are non-conductive. The help seal out moisture and lube plastic connectors, but I don't understand how they could improve electrical connections.