I had mine in yesterday for the exact sound(2019 Heritage 114 1,700mi). I drove it from home to the HD shop about 8 miles and didnt notice the sound as much. They adjusted the belt and said it was a " normal" sound? I drove it home and it wasn't bad at all. However, I drove it to work (55 miles). As soon as I slowed to about 30mph, the wha wha wha sound was back and loud as ever. So is is something heating up?

Back to HD..........

 

Maybe the big pulley is heating up, expanding, and tightening the belt?

It seems to me that the dealers are setting these belts too tight, but you'd think after all these years of experience producing bikes with final drive belt that all the service personnel would have it figured out.

Here's a useful quote
from this thread started later about what is probably the same issue: https://www.hdforums.com/forum/2018-...id-this-2.html

 

With a counter balancer , huge pistons,timing chain,primary chain, gear box,lifters ,push rods,oil pump and four valves , choose your own adventure (sound) to focus on.
But yes there can be a whine or intermittent sound if the belt is too tight when riding.

Peace.