Below is an edited post I wrote from a recent thread about going to S. America.
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IMO, not many guide books or DVD's are as good as current ride reports. These offer timely info from folks out on the road NOW or recently returned. Most of the links below started in N. America and moved South into S. America. But all good info and inspiration. Take your time, read the ones that interest you. Leave the rest behind! 
South America and back on a 250 Super Sherpa Minimalist Adventure - ADVrider
JDowns (one of the best reports)
Jammin thru the Global South - ADVrider
Jammin Jay (Starts in USA, then Latin America and beyond) Great stuff on S.
Chile.
http://www.advrider.com/forums/showt...50+Baja&page=3
Jedi Master S. America (best photos going!)
South for a while
maybe longer - ADVrider
Air Borne Andy (lots of good info)[/QUOTE]
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My .02 cents.
It's beginning Winter now in the far South, so Punta Arenas & Ushuaia may be too wet/cold to ride in June/July/August. By mid-late Sept. weather may get better. By Oct./ November, should be good.
In the meantime you can study Spanish in Quito, explore Ecuador (worth at least a month) then mozy into Peru', visit Toby for the World Class routes and KLR knowledge. Honestly, I would skip Macha Pichu. IMHO, over-rated. I liked Cuzco (was there a month) but not thrilled with the MP experience.
Don't skip Bolivia. ($130 for a visa for US citizens

) Lots of good riding, do research to find best options. (Death Road a must)
Winter (May to Oct.) is best time to visit Northern Argentina (IMO), way too hot in Summer months. Lots to explore and discover there ... and Argentina has the best food in S. America, IMO. If you like Italian food and coffee and the best steaks in the world, you'll love Argentina ...but there is so much more.
When you get your bike crated up I'd love to know the cost of air fare to Quito. Can you post back here when you find out?