I'm looking for a single cylinder road race engine. What do you guys suggest I use. I want liquid cooling, and something that will withstand the high revs of road racing. My first choice would be a 426 engine, but I hear they are impossible to find unless you buy the whole bike. Anyone know a good source for engine only purchase? What about Yam. 660, xr 650, klr 650, crf 450, etc. All coments and suggestions welcome.