A year ago I rebuilt my motor and ever since I have had an annoying vibration in the handle above 5000 rpm. Today I decided to dig into the problem. I remembered that I had to replace two broken motor mounts that connected the head to the upper frame. Well, today I removed them and the vibration went away. I have also noticed that a lot of people on this board have said that their upper motor mounts have broken. Based on this I am pretty sure that the warrior has a resonance problem between the engine and frame. I would recommend that people leave their motor mounts broken or off. I am going to try to fab up a rubber mount system for the head. I'll post pics and directions if I am successful.