only kept the engine. minimal chromoly frame, carbon subframe, carbon seat, tank, fenders, fairing, marchesini aluminum wheels, titanium exhaust, carbon engine covers, my own aluminum swingarm, titanium and carbon mufflers, very minimal fairing brackets from lasercut aluminum, airbox replaced with stacks and foam filters, took a few lbs off the flywheel. the subframe/seat is too heavy still though, since I made it from 4 distinct pieces. It could be one and still lighter. the fairing can be made still lighter by building it thinner but as hollow glued up assemblies, which would then mount directly to the frame, eliminating any metal except for the screws. if it were a race only bike, the headlight, lighting, lots of wiring and switch gear could also be removed. I could possibly go with titanium for the frame and reduce 4-5lbs there, but I couldn't transfer a stock steering head in that case, so it would be track only.