Original Athena cylinder. The racing version of Athena offer the power among the best of the Mid-Race range, a very durable nikasil plating inside together with the fast heat shifting nature of an aluminum cylinder ensure excellent reliability. The main differences to the Sport Pro are longer port durations, a bridged exhaust port which makes for huge port time area and a higher compression ratio. Needs at least a 17.5mm carburator or bigger, together with Yasuni R, C16, ForRace or stage6 replica this will yield excellent performance. Comes with a specially coated Asso piston, a set of carbon reeds and a variety of base gaskets to adjust squish clearance.