When your dealing with such small displacement engines to begin with, 18cc is a lot. I would think the 97cc would be a bit better. Either way, that go kart could probably get beat by a power wheels battery powered barbie jeep. Not giving you a hard time, just figured I'd say it before someone else did. On a more serious note, I wouldn't bother changing anything around just to swap to an engine that is about the same power.