1020 big bore designed for the 1000cc models. The 1000R (maverick head) kit is 12:1 compression, made to run 91 octane pump gas. The ATV head kit is JE pistons 12.5:1 compression, made to run 91 octane. Kit comes pistons, rings, clips, wrist pin, head and base gaskets, bored cylinders. We need your cylinders to bore. Fuel tuning required.