Hi
Measure the width of exhaust port. I am read that a width equivalent to 60 % of piston diameter is a good number to have good torque.
I have widened a moped engine exhaust port at 60 % and runing good.And have a good life also.
This ratio is to have a safe port width to not allow the ring to go into exhaust port when going up.
If I remember well , the ryobi have a exhaust port with an aluminium piece in the half, do not remove it, it make the life easy for ring , and you have two halves, each at 30 % width of piston diameter.
Of course, you must round very gentle all the ports enlarged in the cilinder surface to avoid scratch the ring.
Others readers in the forum can help with it ?
I have a weedeater engine converted in a test stand and it have a 60 % of piston diameter in the exhaust port in stock form. Aprox 34 mm in piston diameter and 20 mm aprox in the exhaust port width.
Good luck
Have fun
Jose