I have read several books on this and the most popular bike seems to be a BMW I think its called the R80. Says you cant fix with about 4 spanners and get parts all over the world.
Bugger if I was free and single would love to attempt something like this.
Ken
The books seem to have hit a bit of a platea. Chris Scott's Adventure Motorcycling Handbook is so good no on has really done anything like it since. This was written in the early 1990's and while updated since he add's rather than rewrites.
This means while he talks about the condition and preparation in another chapter the R80GS stuff is as it was in about 1995 when rather than a 20 year old bike with mising gearbox circlips and worn drive splines, you could get a six year old bike and do what you liked using bits from 8 year old scrappers. The competition on 1995 was a Tenere that was equally out of production and used the same technology made to a lower price.
In to the mix also goes people who just won't give up on the old beasts. There is a guy who pops up on HUBB that will tell everyone that an R80GS is the ultimate bike. His however isn't off e-bay yesterday, it's a HPN frame and forks with a R1100 FI system, reworked gearbox and specially made hardened final drive. This is an air-cooled flat twin, but for what he's put into into he could have had a new BM and a new Tenere.
If Chris Scott had included 20 year old bikes when he'd written the AMH, Ted Simon's Triumph would have been in there too! It is, but it's lumped in a general section called rat bikes.
IMHO, it's about the condition of the bike and your knowledge of of, not what the marketing man or authors back when tell you. The CB500 is pretty close to a modern version of Ted Simons Jupiter, so I say that's the better machine.
Andy