Valve & Valve Spring : In order to obtain a smooth rotation feeling and smooth power by high rotation, lightweight-izing of a valve system is important. Moreover, a valve spring is effective for a torque rise of an inside low speed by uniting with the same rate. In consideration of the thermal efficiency of a burner, the stress of a valve sheet, and the flow velocity in a port, polish machining of the valve was carried out, it reduced resistance to the limit, and united weight.