Four-cycle engine

摘要

A first catalyst 9 is arranged in an exhaust pipe 6, a second catalyst 10 is arranged a space apart from the first catalyst 9 in the exhaust pipe 6 downstreamof the first catalyst 9, secondary air induction pipe 11 for introducing secondary air is connected to a portion of the exhaust pipe 6 between the first and the second catalysts 9 and 10 and to a position where a difference between maximum temperatures in measurement operation areas of the first and the second catalysts 9 and 10 is in a predetermined range.