Thanks guys, I will check out e-bay. I actually checked the spark plug and that's what it was. I was surprised to see it just fowled up while I was riding it, but I'm new to this machine.
I have started to take apart the bike and inspect it, and have dicovered other opportunities with maintenance that the previous owner obviously did not pay much attention to. This is going to be a fun project...
Another question:
Is it normal to have black "gunk" in the muffler? I took it apart and am in the process of cleaning it. It seems like the machine was run with the wrong mix at one point (or throughout), and this goop has collected in the muffler.