Hi, I had a KTM640 (normal, not the Adventure model I think) rented for a few weeks in Costa Rica earlier this year, and I would agree with the previous poster here, its good when you ride solo,
bad or even very bad when you go 2-up. It starts to feel underpowered, shakes way too much at nearly all rpm, the seat (and space overall) could ve much better,
and the gearing is for offroad, on paved roads you´ll always think you have the wrong one on (this, too, was a problem only when riding 2-up).
Sure it may be a very robust adventure bike, and in fact it was great when doing some of the worst-condition stretches or even tar-roads,
while riding by myself. But it simply wasnt made for 2-up riding, and indeed my girlfriend said this was the last time she´ll climb on the back of a 640. If
I were in her position, Id probably think the same. Didnt let that ruin our holiday, though..!
If your going on a long trip with 2 people on the same bike, I wouldnt even consider this model, there are others that are so much better suited for that.
Theres a magazine in Finland, which now features a trip from here to Vladivostok (and back!) with a 640 Adventure, that guy went solo. I think he had a subframe break up somewhere in Siberia, managed to fix that, though.