The past few years I have been slowly trying to get a flat tracker together. I had a TT500, was ready to race (I think), and had an offer to sell. Recently, I bought back my old pile of spare TT/XT parts, thinking I would going to build another one. But, an old family friend of mine wants to help me put a two smoke together. He was a Yamaha mechanic back in the '70's and '80's, and that is what he would like me to build. So, this is what I would like to do. There is a "local" series, the Classic Flat Track National Championship Series (http://bikedays.com/id52.html), that has a few half mile races a year. Usually, two are held here in Iowa, Davenport and Knoxville. I want to run the V250/360 class. Back in the day (1973 to 1976) that meant 250cc two stroke twins, 360cc two stroke singles, and 360cc four stroke singles and twins. From what I have seen, the Honda XL350 owns the class. I have not seen many smokers. For me that is great, because I would rather be unique. So, what I am questing for is technical information. I would like to put together a RD250 and a DT/RT/YZ360 powered Champion. Which engine/year/model, for each, was/is the hot setup? The reason I am wanting to build both, is because I think it will be harder to find a Champion frame for the RD, so the DT will probably get built first as I find RD parts. Then, the DT will probably get switched to a short tracker or TT bike.