Read Long Way Down and Long Way Round. Those books and a week off in a tropical country are a bad combination-they put crazy ideas in your head.
I'm much more of an off-road guy and I only really want a street-legal dirtbike so I don't have to trailer it, but a big trip like this is getting more and more tempting...
Even better, my grandfather is still around and still riding and ideally I'd like to do a trip with him and my Dad. Probably 30 years ago now, Dad did a 30-day trip around the U.S and Canada with a few friends on a then-new '77 Suzuki GS750. I think that's what we'll do to start with, that's probably plenty for my first real trip.