Just got this bike ,'04 flhrsi Got a whistle when between about 40 and 60. It is air passing over something .Any clues ?

It's somewhere out front .
Not sure where from.

Any ideas to isolate things till I find it?

 

take a leaf blower to it and see what spot makes noise ?? I had a similar dealio to you and it turned out to be whistling from the headlight trim ring, I simply used a hung of tape backed foam weatherstrip behind the trim ring and it was gone.

 

Check all your mounting points up front (windshield, passing lamps, trim rings, nacelle) maybe something worked loose a bit. Nice bike BTW mine started out like that then I got a wrench in my hand!

 

I agree with bigheadted. Mine started out with a single head light. I added passing lights. Then I added trim rings, and it started to whistle. Stuck a little weatherstripping in them. It quieted the whistle enough for me to forget about it.

 

I sure hope you guys are right about the trim rings!
I've been having the same EXACT problem, and it's been driving me NUTS!!
I was surprised to see the chrome mini shield still on your custom when
I first read the post, because mine was fine, no noise at all until I removed
that shield! As soon as I took it off, it whistles between 44-55 or so.
I even tried the ashtray shield under the forks which helped some, maybe 20-30%
but could never get rid of the rest of it.
Now I have something new to try, thanks for posting!