Vibration under acceleration

Hi
I have a 2000 RSV Mille it is a good bike and i am mostly happy with it but..........
Under acceleration it doesn't have vibrate (Like a jack hammer!!)
It has oil pressure and seems almost smooth on constant throttle (Sometimes) so I don't think the mains are on their way out (Unless you all know different)
If it was a inline 4 like most of my other bikes I would point my finger at the throttle bodies being out of balance (Though an in line 4 wouldn't generate that amount of vibration) so my questions are:
If it is the throttle bodies can they affect that much even though it is only the bypass you adjust and it happens at all revs right the way upto 10000rpm?
Could it be the mains?
Could it be the balance shaft, or would this show up differently?
Could it be the engine mounting bolts? (the bike is a Cat C so someone has rebuilt it at some point and may have missed a spacer or bolt!! going to check this tonight)
Is it a knackered chain? (The chain and sprockets aren't brilliant but not 100% shagged out)
Could it be something else I have not thought of?
I have had a bit of a search but nothing definite turned up.
Any help gratefully received.
Thanks

I will do but it is definately engine speed related

Checked the engine mounting bolts and the bottom left was finger tight!!!
Checked the Rear Sprocket bolts, all finger tight!!!!
Set chain to the correct tension
Not got a chance ot take it out tonight, hopefully will give it a spin tomorrow