For me I'd say tyres are the biggest thing. I've had hellish days on snow, sand or mud covered roads and tracks because people brought big trail bikes on road tyres or simply couldn't ride them (and though BMW fitted some sort of trail magnet). I've likewise put semi-knobblies on Triumph Bonneville and taken it to the same places in similar conditions having great fun. There are days and tracks where only a 250cc MX bike gets through, there are others when a Harley Dresser makes it.

My experience is limited to Europe and North Africa (I can never get enough time off work to do the rest ), but i'd really say it depends how you ride. Which is worst for you, a day at less than walking pace in the mud (never had one myself), or doing 25 mph on the motorway while the trucks howl past in a cross wind (the XT was down to 35 in places)? Can you live without a spare sleeping bag or do you need the 60-80 hp to lug your gear? How tall are you? How skilled off road? How upset do you get if you have to take a 100 mile detour because it decides to rain?

Trail bikes tend to have fewer things that drop off or get ripped off when they meet the mud. My BMW F650 and Yam XT had nothing modified except tyres. My Bonneville has a new set of silencers about every two years off e-bay because I ding 'em and they rust faster than normal. For a bigger trip with more than a few miles off the tarmac I'd need to do a proper exhaust mod to prep the bike. It might well be easier or cheaper to just go buy another F650.

At the risk of starting a fight (and please remember I'm 5 foot 7/1.7m and weight 75 kg) I'd say a BMW R80GS or ST or F650 was about right for how I ride (The Bonneville with knobblies is similar) while XT's are heading towards too much trail bias and KTM's are just too much. That's only for me though.

Andy

A good reply and summary there Andy: was there any particular reason for the XT (XT350?) to get down to that speed?

Bobby,
A fair enough question: as you say, it is very general though. I guess you will get a wide range of responses therefore.
As for Andy, I have no specific experience in South America: therefore I have read quite a few of the threads for that region and in "which bike" on this type of question + a few blogs. I recommend that you will get some value from doing the same.

I would add to Andy's reply that the lasting message I have got from such earlier information is to consider the work involved in lifting bikes on and off various forms of transport (such as boats to by-pass the Darien gap) - not unique to South America of course - and the fact that you can expect your bike to be "written-off" by the travelling: both the bodywork and the engine components will be well toward the end of their useful life as the result of such hard usage - obviously this is a generalisation, but check some of the blogs etc for such journeys and the facts speak for themselves.
There are lots of crashes down that way!

ps One of the more interesting discussions or statements from those riding in S America can revolve around what bike they will get next as a result of current travels in that region.

__________________
Dave

This was back in 2004. I took the XT on a circuit of the Baltic. Coming out of Sweden into Denmark there was a massive cross wind and rain/sleet up to and over the bridge. The 21" front wheel with Pirelli Knobblie, plus too much gear had me leaning out of the saddle using my knee as a sail for 80 odd miles and just over two hours. Anything over 35-40 mph and the gusts had me out of the motorway lane before I could correct. The word SCANIA seen close up in a mirror still makes me shudder! The fuel consumption was down in the 40's as I needed 4th to drive against the gusts, engine brake when they dropped. Bad conditions for sure, but a more road type bike or less stuff or maybe even just TCK-80's would have had it put down as a motorway drone rather than the ride from hell. The Bonneville would have made it along all the loose surface roads I'd done up to there and taken that bridge at 80-90 kph in a nice safe gap between the trucks.

In my case this was fashion (reading too many travel books) over experience. I didn't need the 21" front wheel, the Touratech boxes, the jerry can etc. A low C of G and another 15 horses would have been useful. You live and learn.

Andy