I recently posted that I was considering using the v-belt pulleys that were already installed on my axle for the final drive on the Cycle Kart.  I got some interesting feedback from the Cycle Karting community on the Yahoo Cycle Kart group.  They community seemed to agree that the v-belt would work until I ran the Cycle Kart in dirt or water.  I suppose I could try to encase the belt and pulley, but inevitably water or dust would get in and reduce performance.  That said,  I have begun preparing to attach a 60 tooth sprocket where the pulley is currently.