An engine comprises a first cylinder and a second cylinder adapted to perform explosions at such timing that an interval from the explosion in the first cylinder to the explosion in the second cylinder is shorter than an interval from the explosion in the second cylinder to the explosion in first cylinder, an intake manifold having an intake passage, and branch passages communicating the intake passage with the first and the second cylinders. The engine has at least one of the construction that an interval from the explosion in the second cylinder to the intake operation of the second cylinder is set longer than the interval from the explosion in the first cylinder to the intake operation of the first cylinder, and the construction that an interval in which intake and exhaust operations of the second cylinder are overlapped is set shorter than an interval in which intake and exhaust operations of the first cylinder are overlapped, so as to reduce misfire during low speed idling and to enable the engine to produce large output power during high load operation.