I got it onto the thumb drive. I'll try it on my bike tomorrow.

 

above advice correct. make sure the update file on the flash drive is the root file in other words no 'folder' exists, just the file. i down load to my desktop then 'unzip' to my flash drive. if i remember correctly no 'folder' exists, just file.
then when you insert into bike usb the boombox immediately recognizes the update.

 

Download the file from the Harley Website to your desktop. Right click the file and choose "UnZip." I save the "UnZip" file to the desktop too. Drag and drop the UnZipped file to a USB stick. With Bike off, plug in stick, then turn to accessory and wait for prompts.

 

Success! Thanks everyone!