[Mgs] Motor Vibration

[Matthew Milkevitch]

Good Evening Listers;
   
  I would like to elicit some opinions of the list on something I've observed for some time....motor vibration on my '74 MGB-GT.
   
  While at idle, the motor vibrates quite a bit...it just about "shakes."  I have no idea as to the source of this.  The motor has less than 10K on it (rebuilt about 5 years ago) and new motor mounts were installed when the rebuild was done.  
   
  Can anyone venture a guess what the cause is?  I would imagine there is an inbalance somewhere....???
   
  Thanks for the help,
   
  Matt Milkevitch
  '74 BGT