Well, I'm a noob too and like the speed as well, but it is true that unless your average bicycle is really built for those kinds of speeds, something bad is lurking around the corner.
I got a 80cc on Ebay at a real good price and also got myself a pull start for it (because I'm lazy
). I'm real happy with it. I think you'll find some interesting mods you can do to it as well on this site, that'll make your ride perf'd out.
The second option is the pulse jet!