Does anyone know and good web sites and or books that I could take a look at to learn more about sled engines? I want to learn more about the basics, repairing and maintenance. Also I am thinking about a rebuild on my own engine. I have been told that I can get it oversized. I know what they mean but the process and work involve is unfamiliar with me. Like this much over = this much in power. Any info would be greatly appreciated. I am riding an 89 Yamaha Exciter 570 ex[?].