A little bit more information please.
Do you have a BT headset in your helmet that you are wanting the music to play on?
Are you wanting to play the music on the bike's speakers?
What verification do you have that the music is actually playing off the phone and not playing to BT (if you don't have the BT headset)? IOW, do you hear the music coming from the phone?
It depends on how the bike "sees" the phone since it is designed to work with a music player device. If the bike shows what is playing then the sound should be going through the bike audio system.
There should be a set of icons at the top right of the LED display that shows that input is through BT or USB and output is through BT or bike speakers. Is that set right using the Mode button?
If you do have a BT headset is that also connected to the bike system (Mode + Volume UP)?