Flying Horse 66cc/80cc 2-Stroke Motorized Bicycle Bottom Head Gasket &ndash; Gas Bike Lower Cylinder Gasket The 66/80cc Bottom Head Gasket is the direct replacement for the bottom head gasket on any 66/80cc motorized bicycle engine kit To install, remove the cylinder body and head cap from the cylinder. Remove the stock bottom head gasket and replace with the new bottom head gasket. Assemble the cylinder and head cap back on to the crank case, torque down, and you're ready to ride Compatible with Flying Horse, Mega Motors, Grubee, Power King, Stinger, and most other bike engine kit motors