Most of the Phelon flywheels on Ryobi's are out of balance. ( some early Ryobi's rely on the flywheel for total balance so use caution here)

On my Ryobi, the flywheel was more out of balance than my McColluch, Homelite, or Weed Eater flywheels.

I balance the flywheels on a Dubro Prop balancer and use a die grinder with a carbide A11 burr.