If I remember correctly, the Ryobi 30 is made more like the old Homelite 30?

My experience with Homelite 30's and I currently have two of them is that with running a 18 X 8 prop, a 11.11 mm carb is about all you should have on one.

The gain beyond using a 9.52mm carb is only about 150 rpm.

Larger than the 11.11 mm carb is prone to increased sensitivity of the surrounding air flow and pressure at higher throttle settings.

To even run a 12.7 mm carb, you need increased timing and a smaller prop to increase the rpm to take advantage of the larger carb.

The 13.47 mm carb is the size that are on my BME 50 and Brison 3.2 engines.