0caarntedd 6 years ago ReplyUpvoteA rat would usually be built from any make of motorcycle you can get your hands on for very little or no money. I would suggest japanese due to low cost and high availability. Try and get something that is running, and has all it's original parts (so the numbers match) and a title to save paperwork hassles later. Do you have mechanical skill? The more skilled you are the more work you can do yourself, meaning you can use a worse basket case to start with sving money. There are quite a few cool XS Yamahas getting around, but anything should do. Try googling some chopper forums or "underground" bike builders etc. for building tips and ideas. Also some magazines such as Ironhorse cover alot of DIY stuff.