R850R Lumpy/Vibration over 5000 RPM?

[GadgetMart]

Afternoon gentlemen, my first post here...

I have a 2005 BMW R850R, single spark model, it runs sweetly, however 5000 RPM and above there is considerable vibration, so much that it is difficult to see out of the rear view mirrors.
I have checked and adjusted the valve clearances, synchronised the throttle bodies and checked the spark plugs.

Suggestions please appreciated.

Thanks.