Abstract: An improvement of an exhaust gas cleaning system for an internal combustion engine which is provided with a secondary air feed system connected to an exhaust port and a reed valve device opened on an exhaust pulsation pressure arising in the exhaust port to feed secondary air to the exhaust port.The secondry air feed system has an upstream side secondary air passage through to the atmosphere and a downstream side secondary air passage formed on a thick wall zone of the internal combustion engine proper and connected through to the exhaust port. The reed valve device has a valve casing installed on the circumference of the engine proper, an inflow port connected to the upstream side secondary air passage, and an efflux port connected to the downstream side secondary air passage. The valve casing is partitioned internally into an upstream chamber provided adjacently to the engine proper and a downstream chamber provided on a side away from the engine proper across the upstream chamber.