Here is a cool article that I scanned from a 1979 issue of Cycle magazine I have in my collection. This article covers the details of Mike Bell’s Dave Osterman-tuned factory Yamaha 250. This is from the days of true works bikes when Bell’s machine did not have to share anything with the stock YZs of the time and is a cool look at the technology of the time.
themotocrossvault.com 