ICE: Internal Combustion Engine.
Hopefully somebody who knows more about it will chime in here John, but I think electric is more the specialty of the house. It sounds like you`ve already looked into some of the more gas oriented sites, but I don`t know which. Yeah, I think it would be pretty tough to put together a 4-stroke drive for that price (I could be wrong). Have you gone over the newb FAQs over at motoredbikes.com? Here`s the general purpose one and they have a lot more in the subforums.
http://www.motoredbikes.com/showthread.php?t=10392
I`m guessing friction drive is the most economical way to get yourself rolling. They have a subforum specifically devoted to that also, with its own FAQ. Good luck with your project.