There's no replacement for displacement. Pro-Tec's 727cc Yamaha Rhino big bore kits will provide the low RPM torque for racers who crave the holeshot and recreational users who want to be the king of the hill. Pro-Tec's 727cc big bore kit includes a centrifugally spun, centerless ground, chrome-moly cylinder sleeve, lightweight forged aluminum high compression 105mm piston, and 105.50mm OEM quality head gasket. Pro-Tec's 686cc big bore kit can be purchased with a 10.75:1 compression piston for those who want to run pump gas or a 12:1 compression piston for those who choose to run race gas. The 686cc big bore kit includes a lightweight forged aluminum 102mm piston, OEM quality head gasket, and bores into your stock cylinder.