Congratulations on the new ride! Check for this subject on the general discussion section and click on search this forum with whistle as the content. You will find what you are looking for. I do not believe there has been a solid fix for this but my '15 has it and the MPH range is over a greater span than 50-60. Took it back to the dealer for many things and told them about it. They got back to me a couple days later and said they did not hear it. When I went to pick it up and talked to the GM, we walked up to the bike and he was asking me details about the noise. He said they were unable to duplicate that noise, I turned the ignition on and it had the same miles as when I dropped it off. After I pointed that out to him, he was speechless and I have just been dealing with it since then. Way to go Dealer!
2019 Silver Flux/Black Fuse FLTRU