my favorite: honda nx 250!

have been travelling tough roads with this extremely light, small and economic bike. algeria (hoggar south, b.o.d to illizi), south america (for example: uyuni to san pedro / pictures here) and morocco (taouz-mhamid etc.) - no problems so far...
the small size of the bike gives you full control even in dangerous terrain. with a "white power" rear shock absorber you will be ready for any challenge, even with lots of stuff (the original absorber is the one weak part of the bike). the fuel comsumption of 3-3,5 l /100km saves a lot of money and logistics while travelling long and "dry" roads.
the honda nx 250 is extremely reliable - my south american one is looking back on 110000 km. there has been no breakdown, no mechanical problem - nothing.
this bike is cheap in germany (built until 95), and - because it is a favorite by women - usually in perfect condition.
you will need the original 20kw for sandy deserts, most of the older ones have full power.
one problem are the tires. the front one lasts about 35000km, so no problem here. but the rear one (120-90/16) is virtually not available in poorer countries. worse than that, life expectance of both available products adds to only about 10000km. so bring along two, if you're going a long way from home!

with a bike like this i'm sure you will share my travel experience:
half cost - double fun!

good luck to everyone