gooday. probably not this. but your symptems sounded much like what i had a while back. vibrations so bad i thought a mount had broken. . i removed primary just incase it was compensator nut loose.. checked wheel bearings.. all sorts of stuff. turned out to be a stone the size of a 5 sent round, jammed between the primary case and the frame adjacent to the rear footboard.. on a roadking. . couldnt believe such a little rock could cause so much concern.. might pay to check any small gaps betweeen engine and frame for such things.. hope it helps. cheers

Sounds to me like the flywheels have shifted or the connecting rods have been comprimised. can you hear this noise while the motor is at idle  ?? or is the noise happening only when the bike is in motion ??  dsv

 Jack it up and Drop the one of the bolts out of the shocks and see what gives when you put pressure on the swing arm.

From reading the above posts my guess would be swing arm or shocky bushes.

It can be difficult to find movement in swing arm bushes when the bike is all together, you may need to get it up on a stand take the shocks off (check their bushes) and let the tension off the belt then start shaking and wigglin the arm, sometimes you may even need to take the wheel out to get all weight off the swing arm before the movement will actually show up.