My first mod was extra brake lights in the side pods. Next up was a 15T front sprocket, oh so nice and mileage jumped to the low-mid 60's. Since then I've swapped most of the lighting over to LEDs, painted the bike Atomic Orange, and installed foam grips (no more numb, tingly hands!) I've got a Corbin I only use for long trips, and added a Mike's Euroshield. Oh, and an external fuel filter.
Currently I'm working on a new instrument cluster, I really want graduated and accurate oil pressure and coolant temperature gauges.
