Yamaha TTR 250
They say size matters well this quater litre bike of mine had already been half way round the world when i got it.
Since then its been used for commuting, racing, green lanning and touring.
I rode it to Morroco no worries whatsoever. I think you can tour on any bike you just have to be realistic in what you want to achieve. A small light bike with a simple load can make travel very easy, obviously distances take a little longer but then hey ho you get to enjoy the scenery more. I also think locals can relate to you more when you are on a smaller less intimidating bike.
When you get stuck a small bike is easier to get out than a big heavy beast.
So travel light enjoy the ride no worries