ZENOAH 34mm 25.4CC BIG BORE KIT34mm Big-Bore kit from Zenoah for the RC engines. Increases displacement to 25.4 cc. Includes 4 transfer port cylinder, piston w/ring, Champion RZ7C spark plug, piston pin, cylinder gasket, and clips. Increases engine power SUBSTANTIALLY! This high-performance product requires 91 octane (R+M/2 octane rating) or higher fuel, and comes without warranty. Note: if installing this product onto a Chung Yang engine (CY23RC, CY26RC, etc), you will need to use a Zenoah pin bearing (DDM part # ca217) and Zenoah pin washers (DDM part # ca216). Zenoah part # GR23199 Interchangeable with HPI part # 15485 Stock part on the Zenoah G260 engine