Newbie owner.. Whats a BWS 100 meant to sound like under deceleration?

I recently got myself a 2006 Yamaha BWS 100 with 13000km on the clock. I've owned 2 strokes before but never a scooter and I'm trying to learn about the new noises.
My main question is what what is the bike supposed to sound like under deceleration? I understand deceleration on geared 2 strokes but how does it work with a cvt and how is it supposed to sound?

The bike sounds great under acceleration and idle but when it comes to deceleration, especially from high speeds, there is quite a loud whining noise and sometimes a rattle. Is this normal?

 

It could be the gearbox whining on over run and rattle could be rollers in variator. In the scooter world it's very old and I'd say quite rare now.

 

Awesome thank you. Is it necessary to inspect the gearbox if it whines?

 

Just make sure gearbox has oil, ep 80/90.

 

Thanks a bunch.
Last question for now. Any ideas on the best parts suppliers? I live in Cape Town and parts are still readily available from Yamaha although rather costly. Are aftermarket parts for these bikes viable? Are there any manufacturers I should look at or avoid?

 

Genuine parts are always best, the 100cc is very rare here in the UK.