This is my 1967 YAMAHA YDS5E. My brother, Hal, bought this bike from the original owner in 1969. We traded it back-and-forth for a couple of years and I've owned it ever since. I restored it in 1992. These machines were rated at 29.5 HP @ 8000. Note the improvement in engine performance in just the ten years, and six production models, between the YD1 and YDS5E. Oh, yes, the "E",in this case, indicates electric starting capability.