Funklab, if you think you can ride 'round the world on 30 grand, you're in for dissappointment. It ain't about money, it's about attitude. What's in your mind, your heart and your guts.
Please allow me to explain.
I could provide you the names of people who toured the world on the ultimate bike of the day, got bogged down in a little mud, and left it there to fly home. Spoilt brats.
Then I could mention those sportsmen who toured the world with a van and a movie camera filming every second of their ride, so they could flog it on TV when they got home. Rich spoilt brats.
But I'd rather give you the names of those who did go around the world, on a budget, and budgeted their expenses by working a few days or maybe a week here and there, small jobs to earn enough to get by for another month or two. One of these guys rode a Vespa from Italy to Japan for the Tokyo Olympics in 1960, another decided he was bored with life and rode from Italy to India and got back two years later, sober as a Quaker and with more money than what he left with. Then there was that journalist who left London under pouring rain, and wanting to RTW ended up in Egypt the very day the 1972 Yom Kippur war broke out... he survived that, ejoyed the Sudan, explored Ethiopia... his name was Ted Simon, and he wrote a wonderful book, "Jupiter's Travels", I highly recommend it. Read "Investment Biker" by Jim Rogers, a highly entertaining read (he and his girlfriend rode two BMWs RTW twice!)
One good piece of advice, stay well away from spaceship technology, R6, 12000rpm japanese bikes in general. You want something that you would be comfortable with changing a tire at the roadside, or asking the local mechanic (in Chile? Guatemala?) to change piston rings or a distribution chain. So my advice is a good 1-2 cylinder dual sports .
Another piece of advice is, don't ride something that, fully loaded, you could not pick up just because it fell off the sidestand.
Last, nothing that looks too expensive. Never mind what's cool and what's not, you want something that won't attract too much attention as you enjoy a well deserved

, or that won't draw bribes at border checks.
From a "foreigner's" point of view (I'm Italian), one major setback you have is your Passport, you're American, you come from the richest Nation in the world, be proud but don't flaunt it.
Bikes go by personal preference, I've always ridden mid-sized Moto Guzzis or BMWs, they're tough as tractors and will pound the highway 24/7 if they have to, and never overheat. Ever. If that sounds too expensive, remember, a good quality air cooled engine is better than a mediocre water cooled engine, and shaft drive (or belt) is 1000 times better than chain.
OK, 'nuff now, else I'll be hogging the thread. Feel free to PM me if you want to visit Europe, and remember, the juiciest bits are always off the beaen track!
8^)
Maurizio from Rome, Italy