I beleave it was 6.1:1 ratio and 39 horse wasn´t bad if you consider it´s curb wt was 315. For the early 70´s it was one of the hottest bikes on the road. They discontinued this model and came out with the RD 400 that was 40 lbs. heavier and 1 horse less in something like 77 or 78. Too many people were getting hurt by pulling the 350´s up over and backwards.