1990 FJ1200 Vibs

[wainot-Phil]

hi all ,,I have a 1990 FJ1200 , Done all the normal FJ Mods ,,plus  New Plugs ,Set Mixtures, Balanced Carbs ,the Bike starts and runs clean through all Rev ranges,,Good power and she Revs Quick and clean , The Motor also idles Smooth as Silk,
BUT MY PROBLEM IS   
with the Bike on its Centre stand and with Motor running its fine up to about 1500 rpm ,then after 1500 rpm a harsh Vibration waves right through the whole Bike ,,like a metal to metal vibration
I have pull and Greased the Front Engine  Mounts , Balanced Carbs, Checked Shims ,etc etc
The Bike has a harsh Vibration which radiates right through the Bike when bleeping the throttle  1500 rpm and onwards ,,

The only thing I have not done ,,,is looked at the Rear Engine Mount ,, Has anyone in FJ Land  removed and greased the Rear Mount ,,Is that even possible
Any ideas as to what might be making this harsh Vibration right through the Bike from  1500rpm  onwards ,,,while the Bike is just  sitting on the stand ,,  You can  notice the Vibration while Riding the Bike but you get used to it ,,
I have a 87 and a 94 and they are both smooth as silk between 1500 to 4000 rpm with out any vibration at all while sitting on stand  ( I must say the 87 has a  Rubber mounted 97 XJR Motor that I put in it ),   It almost feels as if the Motor is Hard Bolted to the frame and the Motor can not move at all with out shaking the Frame and everything attached to it,,  Its a Bugger because its in great condition ,,,  It is Strange ,,
Any Ideas ,, thank you