Hi ronaldfurtado.
This seems like a wonderful & hardcore adventure you are going for. Good wishes
.
As Ram mentioned, I hope you have seen my Colombia ride in the Touring page on my website as well as my Resources page for some basic information. Again, my rides are more the fly & ride, whereas yours is going to be something entirely different.
Regarding South America, first & foremost, if you want a really complete experience, please do learn some basic Spanish. Although not a necessity, but makes the trip so much more enjoyable when you can interact with the locals on a whole different level (ofcourse Brazil speaks Portuguese). Me & wife managed with google translate, but when you are looking at staying 3 months you will definitely need more knowledge of spanish. The people in general are very simple, very friendly and hospitable. Its surely a lot safer than how the media portrays, ofcourse, as long as we use some measure of common-sense and dont end up at the wrong place at the wrong time.
Dont know what your ride plans are, but if you plan to ride from Mexico down to the extreme bottom at Tiera del Fuego, there are lot of border crossings and getting a foreign registered bike on Carnet thru some of these crossings some times can be time consuming and definitely spanish talking skills will be a major advantage. From what I have read, bikers are generally advised to avoid central America with exception of Costa Rica. Even in Mexico there is a recent case last month of a US rider missing. Not discouraging you but just putting across some of the facts.
As for bike selection, if you are doing a solo ride, although I am a big fan of BMW, for south america, I would ideally select a KLR650. Firstly, if you plan to camp etc, you will have a lot of luggage so its going to be a handful even with a KLR650 as there are lots of non paved/bad roads which get really treacherous when it rains (and that happens very often in that part of the world), so riding or picking up a dropped fully loaded KLR in slush is a lot easier than the BMW 1200GS. Besides, with all the new electronic gizmos on BMW bikes (incl the F800), its going to be a long shot in some of the countries in the event of a break down. Whereas the KLR can be serviced by most good mechanics and parts would be a lot more easier to source or substitute from some other jap bikes. You should be good to go carrying some basic parts like spare set of chain/sprocket, spare brake/gear lever and regular other stuff. Ofcourse if riding 2-up the 1200GS would be a better option, but you will need some basic off-road riding capabilities as that bike is a different ball game with a passenger and luggage in slushy roads. Again bike choice, whatever floats your boat.
Maybe you are aware of the following. For such a project as yours, you can dig for lots & lots of information on the following websites:
www.advrider.com www.horizonsunlimited.com
The inmates there are more than eager to help with any information. The answers on advrider are quicker, but HU takes a lil longer, so be patient. Also for country specific queries, instead of putting your query in the 'Trip Planning' section, you can put your queries on the 'Regional Forums'. The local riders will check more often in that section and you are more likely to receive better responses there.
Anyways, for a start these are the only points I can think of but should you need any other info, pls do let me know.
Regards,
Haroon