I get quite a few people coming here as a result of searching for the phrase "build your own motorcycle". I think this is because of my posts on the ugliest motorcycle (also on Ratbikes here). So I decided to take a look at what comes up in a search and found that most of the sites have nothing to do with actually building motorcycles. One was a site which showed a computer built in the shape of a motorcycle. Others described options available for custom cycles (in my opinion choosing wheels and colors from a catalog is hardly building your own motorcycle) and nothing really covered the design of the motorcycle, but at least this page from Miller Welding covers the welding techniques used to put together the frame.
If you always wanted to know the practical difference between GMAW and GTAW that site is the place for you.