I ran the 17/42 initially on my America, but changed to the 18 as I always wanted a higher gear. After getting used to higher revs, I actually liked the 17 better on my stock 790 bike other than highway riding. I now have a 904 and feel the 18 is the best all around. I didn't like losing any snap on starts on my stock bike, but the extra torque of the 904 gave it back to me. Never considered the 19 due to giving up the quick start fun.
