After mentioning motorcycle kits and components I noticed these two links describing the process for building carbon fiber bicycle frames. Super light and super strong, carbon fiber is showing up in all sorts of vehicles. I previously mentioned one company building carbon fiber motorcycle frames for the chopper market but when you look at the work these two did, you get the feeling you could adapt the process and do the same for a standard or sport motorcycle.
The process involves sculpting a styrofoam core, giving it a light fiberglass covering and then wrapping it in carbon fiber. If you used a standard motorcycle frame as your guide or even one of your own design, following this process, with some modification and adjustment to take into account the greater stress and loads of a motorcycle, you could have your own carbon fiber composite motorcycle frame. Not as cheap as a standard metal frame but a whole lot lighter and, if built correctly, stronger.
Carbon fiber has been around long enough for more home builders to be able to get into this. Carbon fiber is still not cheap, but if someone developed some skill here, they could be on the cutting edge of the next big thing in motorcycle frames.