Keep the Ryobi 30cc.You're getting a better deal than the older 31cc.That newer version is a four port 30cc engine and it is actually made by Homelite. Homelite parts will fit it and it can be modded to give more power and rpm.I have one converted to a water cooled boat engine and I love it .I've had Zenoahs and Sikks,but this engine is more reliable than those.It's not as fast as they are ,but fast enough for me ,a non racer.