Excessive Vibration

[4CooperRacing]

I just finished changing out our 50 motor with a 90. Got it dialed in and it's running great. I am getting excessive vibration in the nerf bars and handle bars that I know will drive my son crazy. This vibration was not in the nerf bars before with the 50 motor on it. There was some in the handle bars before but I made it tolerable my injecting silicone into the bars. Is there anything else I can do or correct to make this more tolerable for him?

[Pappy]

our 2 stroke 90 vibrates also. but at wot he says its not noticable to him