I am riding a KLR 650 for most of my trip from Alaska to South America. There are a few reasons for this;
This bike is simply a shitload of fun to ride. I stepped onto it at the shop and it was down between this bike and a BMWGS 650. Pure & simple, not only was (and is ) significantly cheaper, it is also just that little bit more untamed and wild and that just feels awesome.
Repairability (that's a word right....?)
In a trip of this length, there are going to be things that go wrong. Tires will burst, chains will become loose and things will need to be lubed (heh). I wanted a machine that I would be able to repair or, if it is beyond my ken, easily done by any local mechanic. This was the real deciding factor between the BMW GS 650 and the Kawasaki. There are horror stories that I have found through talking to people of BMW's and other "Western" big bikes that had to wait for months to be repaired or parts.
Lets face it, the cost of a BMW is at least 2-3 thousand more than the KLR. Having finished university only recently, funds are at an all time low and therefore forking out for a BMW, when I could have a KLR, with panniers, skid plate etc all done for the cost of just the bike itself.
Whilst I am yet to see if this is true, I will let you all know but the fuel south of Mexico is apparently of a lesser quality than that typically found in Canada and the US and bikes like the KLR find this easier to handle (the degrade in fuel quality that is ) as well as if it does go all to shit, I can rebuild the engine myself. (When I say me, we all know that means some poor bastard who doesn't speak any english and is having to deal with an ignorant Australian who should have read more about engines before doing a trip of this nature.)