Replying to Crazy idea

So last night I was trying to dream up a project to work on over the winter in my spare time. I was thinking something motorized like a go cart, mini bike etc except Ive already made a gocart. I have an extra lawn mower engine in my garage, with a vertical shaft so I thought of the ratical idea of making a tow rope in my garage. I should be able to get almost all the parts free because my unlce owns a construction company which he said he could supply me with metal. So lets hear some opinions? Ideas? Thanks