The accepted standard is to mount the flywheel true on an arbor in the lathe and turn the fins off flush with the highest point of the counter balance. This usually changes the original balance of the flyweel very little.

But I have seen on here where they were mounted in a drill press chuck with a bolt and spun against sandpaper.

I've also seen the fins broken off with pliers and the resultant ragged edges cut down with a carbide cutter in a air powered die grinder.

No matter which method you use, the flywheel should be balanced afterwards. I have High point balncers that can now be obtained from Bennett Built or B&B. You can also use the Dubro balancer. These are the kind with the thin, larger diameter wheels that a arbor rides in.

The flywheel has a taper in the hub. When mounting on the arbor, the outside cone has the pointed end towards the hole in the hub. The inside cone has its flat side towards the hub.

Cut off the heavy side of the flywheel with the die grinder and a carbide bit until you get it in balance.

Some of the phelon flywheels on Ryobi's are not balanced to begin with. This has been discussed on here often. I alsways balanced mine and the engine didn't vibrate. You do what you wish.

Or you can send the flywheel to one of the people on here that do this all the time and have them do it for you?

Enjoy,

Jim