Over a quarter million XS650s in 40 different variations were produced by Yamaha between 1970 and 1985. The XS650 big twin, in America and worldwide has developed a cult following for good reason. At the heart of the XS650 is a indestructible engine. The best parallel twin ever built.. Tough durability, classic look and abundance of cheap parts make the XS650 the perfect platform to build a KILLER Chopper.