wait!
there is a mcyle dealer in peru that posts on the horizon board. he specializes in buying and fully prepping, documenting, and setting up one of several kinds of bikes for budget american travelers. you fly in to peru, ride around a bit till your papers arrive in your name then head out wherever u want.
If come back his way, he will buy the bike back. easy peasy.
one english couple has posted a blog on their whole trip, including chile and argentina etc.
lots of peeps have vouched for this guy, an expat. i think somewhere on this board someone posted his info.
very inexpensive, and extremely practical. let me try to run down his info
http://www.horizonsunlimited.com/hub...get-ride-76478