I cant wait til these come out !!! 105 MPG
 

http://dieselmotorcycles.com/

Only making for the military soon but as soon as the quota is filled, they're bringing out a civvy model.. That has gotta be one of the best overlanders ..in theory anyway.

or alternatively
 

You could consider one of these.. http://www.royal-enfield.de/motorrad...field_hatz.htm

some advantages are, they very simple to maintain, do not overheat when stationary. This means you can park up with engine driving lights/heaters etc, with no worries about a flat battery as it still has electric or kick start. It does even more mpg. in fact with a 20 liter tank ( less than 200 euros) you have about a 500 mile range.
optionally you can have the five speed gearbox with gearchange on either right or left hand side.. plus the action can be 1 down four up or vice versa (either side), it was designed to be ambidextrous to be more friendly to older riders such as myself. low seat height. big wheels for those bumpy roads...

perhaps a tad more power :( Centarus did a parallel twin with double the power with nearly the same mpg but had problems with the frame/vibration. Looked a lovely bike, and I was saving my pennies for it.

0-60 in over 10 seconds!!!!!!! I think I'd trade a few MPG for a bit more acceleration.

Like you need more for hardcore overlanding..thats still faster than a lot of saloon cars. The civvy versions are stated to be closer to 6 seconds which is fast enough for me for that mpg..

plus, they look bomb proof :)