An engine comprising: a cylinder head; and a valve actuating mechanism provided in the cylinder head, wherein the valve actuating mechanism includes a valve, a rocker shaft supported by the cylinder head, a first rocker arm supported by the rocker shaft, a second rocker arm supported by the rocker shaft, the second rocker arm being disposed in alignment with the first rocker arm in an axis direction of the rocker shaft, and a decoupling device switching coupling and decoupling between the first rocker arm and the second rocker arm, the first rocker arm includes a first coupling hole extending in the axis direction, the second rocker arm includes a second coupling hole extending in the axis direction, the second coupling hole overlapping the first coupling hole as seen from the axis direction, the decoupling device includes a coupling pin disposed at least in part inside the first coupling hole, the coupling pin being movable in the axis direction, an urging member urging the coupling pin in a first direction, the first direction being oriented from the second coupling hole to the first coupling hole in the axis direction, and an actuator pressing the coupling pin in a second direction, the second direction being oriented from the first coupling hole to the second coupling hole in the axis direction, the coupling pin includes a receiver portion receiving an urging force applied by the urging member, the receiver portion is located outside the first coupling hole, the urging member is disposed between the receiver portion and the first rocker arm, the cylinder head includes a retainer portion disposed downstream of the receiver portion in the first direction, the retainer portion overlaps at least part of the coupling pin as seen from the axis direction, and the coupling pin has a length greater than a distance between the first coupling hole and the retainer portion in the axis direction. a cylinder head; and a valve actuating mechanism provided in the cylinder head, wherein the valve actuating mechanism includes a valve, a rocker shaft supported by the cylinder head, a first rocker arm supported by the rocker shaft, a second rocker arm supported by the rocker shaft, the second rocker arm being disposed in alignment with the first rocker arm in an axis direction of the rocker shaft, and a decoupling device switching coupling and decoupling between the first rocker arm and the second rocker arm, a valve, a rocker shaft supported by the cylinder head, a first rocker arm supported by the rocker shaft, a second rocker arm supported by the rocker shaft, the second rocker arm being disposed in alignment with the first rocker arm in an axis direction of the rocker shaft, and a decoupling device switching coupling and decoupling between the first rocker arm and the second rocker arm, the first rocker arm includes a first coupling hole extending in the axis direction, the second rocker arm includes a second coupling hole extending in the axis direction, the second coupling hole overlapping the first coupling hole as seen from the axis direction, the decoupling device includes a coupling pin disposed at least in part inside the first coupling hole, the coupling pin being movable in the axis direction, an urging member urging the coupling pin in a first direction, the first direction being oriented from the second coupling hole to the first coupling hole in the axis direction, and an actuator pressing the coupling pin in a second direction, the second direction being oriented from the first coupling hole to the second coupling hole in the axis direction, a coupling pin disposed at least in part inside the first coupling hole, the coupling pin being movable in the axis direction, an urging member urging the coupling pin in a first direction, the first direction being oriented from the second coupling hole to the first coupling hole in the axis direction, and an actuator pressing the coupling pin in a second direction, the second direction being oriented from the first coupling hole to the second coupling hole in the axis direction, the coupling pin includes a receiver portion receiving an urging force applied by the urging member, the receiver portion is located outside the first coupling hole, the urging member is disposed between the receiver portion and the first rocker arm, the cylinder head includes a retainer portion disposed downstream of the receiver portion in the first direction, the retainer portion overlaps at least part of the coupling pin as seen from the axis direction, and the coupling pin has a length greater than a distance between the first coupling hole and the retainer portion in the axis direction.