If you want to ride the length of South America, you don't have to do it self-supported! We ran into a group, Bike Dreams out of Holland riding from Quito, Ecuador to Ushuaia at the tip of Argentina. They are fully supported and having a grand time. For just 8,900 Euros (about $11,400 right now) you could do the entire ride without having to carry gear. It sounds like a pretty good deal. They also do Paris to Dakar.