An intake device for an engine including the first intake valve located at the downstream end of the first intake passage that is connected to the primary carburetor. A second intake valve is located at the downstream end of the second intake passage that is connected to the secondary carburetor in a cylinder. Both intake passages are connected to each other through a pathway situated in the middle of said intake passages. A check valve located in said pathway allows flow from the first intake passage to the second intake passage. In accordance with a second embodiment, the primary and secondary carburetors are configured so that operation of the secondary carburetor is a function of negative pressure in the primary system to remain closed under minimal load conditions.