A few years ago, a guy named Wan rode a 50cc Ruckus 18,000 miles around the US in 6 months.
I love those kind of adventures!
Here is the link to the Total Ruckus site that talks about his trip:
73 Ironhead Sportster
66 CT200/Lifan 140 (Trail 90) Build Report
Some Motorized Bicycles
And an XR100 engine and misc. parts, waiting for the Mad Scientist treatment!