The bike I think Cookie is refering to is a Trek "Classic" and they are 229.99 msrp, come in a 21"; in vivid blue, candy red, metallic bronze, and metallic black/dark silver. I just took a look at one on the floor and I'm not so sure an engine would mount in easily...maybe. The womens bike could take one though I think. This info is in regards to the '07s only.
Not that anyone needs a new bike, but just to fill in the information gaps for future reference.[/b]