The reed valve pack of a kart engine can be fitted with different types of inserts, concerning both the shapes of the insert as well as the materials used. Usually, it is the preparer who modifies the insert depending on how he wants to control the intake of the fuel-air mixture. The resin insert is used when the outside temperature rises, because when compared to the aluminum version, the resin insert does not change its own temperature and, the result of this is, it does not heat up or transmit heat to the fuel flow to the advantage of the final performance.