Modern Buddy

My Blur has always run smoothly until today when it exhibited a pronounced buzzy vibration at around 50-60 MPH. It felt like it was kind of fighting itself to run at the higher RPMs. I don't know what the cause might be. Any ideas or similar experiences?

I would check the condition of the transmission belt first, then the variator rollers (flat spots on one or more rollers). It could even be something as simple as cleaning the trasmission area of old belt debris and general dirt with compressed air.
I would also check the balance of both wheels. Perhaps one or more balancing weights fell off.

Thanks Babblefish (I love D.A. by the way). Felt like it originated beneath the seat so what you suggest is a good idea.

My son lives in the City as I see you do. When these dog-days of summer hit, I wish I lived there too!

Thanks again (and don't forget your towel).