Abstract: An internal combustion engine includes an exhaust system. Additionally, the engine includes a secondary air injection system that injects air into the exhaust system to burn un-burnt fuel that may be entrained in the exhaust gases. The secondary air injection system can include individual secondary injection conduits, each having a check valve, and being configured to inject air into each exhaust runner of the engine. The secondary air injection system can also include, in lieu or in addition, a cooling jacket cooling a portion of the exhaust system between upstream from a catalyst device and downstream from the point of injection of secondary air.