Well I am not the swiftest on the Ryobi engines, but I do collect and restore vintage John Deere garden Tractors. So I have rebuilt quite a few cast iron 4 cycle K-Series Kohler engines, and as long you can find the specs on what the cylinder bore should be, and using a micrometer to check the wear. If the wear is within limits then of course an engine cylinder can be honed and a new ring installed. However if the cylinder is out of round or past its spec for wear, then a bore job is needed. Since nobody offers oversize pistons and rings for these...then yes a new cylinder and piston would be needed. I don't know where you would find the specs for these engines though. We need somebody to start making oversized pistons, bored out heads, and then lets talk nitrous injection!LOL Of course that would not be cost economical, but the idea of a hopped up engine being a weedeater one day to aiplane engine the next amuses me, and I find it quite interesting.