As crasher says the rear end noise could be tyre related, the drive belt can also be noisy. As for tappet and engine noise, I solved that by using Amsoil in the engine and primary, there was a very noticable reduction in  primary and engine noises.

Bt

Amsoil is one of the best synthetic oils for ya scooter. Its funny you should mention about the whining, my bike is nearly 2 years old and over the last month or so I have noticed a very soft whine kinda sorta sound ? I think it might be tyres (put a new front on a thousand kms ago) or belt but not sure yet.

I to had a very loud whining noise comming from the back end of my bike when i first got it. It was very annoying and it seemed to get louder the faster i went, it was really bad when i was cornering fast and over taking on double white lines..... i left the missus at home and the noise stopped...problem solved.

Steve check out the plastic splash guard in front of the rear wheel. the belt can rub on it if the wheel isnt adjusted correctly. You might have to remove the lower belt guard to see it properly.
Joe.

I had a weird whiney sound on the rear of my WG. Only noticeable at under 65k and even more when de-clutched. Turned out to be just the rear tyre as it either slowed down OR changed its angle to the road. Was noisier around a low speed curve than a low speed straight.