The invention discloses a general gasoline engine, which comprises a general gasoline engine box body, two general gasoline engine cylinder heads and an upper air passage assembly, wherein the two general gasoline engine cylinder heads are connected with the general gasoline engine box body, the upper air passage assembly surrounds the outside of the general gasoline engine cylinder heads, and comprises a fan cover and a flow guide cover, and the flow guide cover and the fan cover are matched in an inserting connection mode and are used for forming a cooling air passage through which cooling air flows between the two general gasoline engine cylinder heads. Through the inserting and connecting type matching between the flow guide cover and the fan cover, the matching among all components is tighter, the sealing performance of the cooling space is improved, the airflow loss in the cooling space is reduced to the greatest degree, the heat radiation effect is ensured, and the integral structure is compact; in addition, the realization of the structure is simple, the operation is convenient, the dismounting, the mounting and the maintenance are easy, and the replacement is easy.