SADDLE-DRIVEN VEHICLE AND SINGLE-CYLINDER 4-STROKE ENGINE UNIT

摘要

The purpose of the present invention is to provide a saddle-driven vehicle which has a horizontal-cylinder-equipped, single-cylinder 4-stroke engine unit installed therein, and is capable of increasing purification performance of exhaust gas by a catalyst, and suppressing an increase in the size of the vehicle in the vertical direction thereof. An engine body (20) has a horizontal cylinder (22). A single-combustion-chamber exhaust pipe (34) is positioned so as to extend in the front-rear direction of the saddle-driven vehicle (1). The single-combustion-chamber exhaust pipe (34) is connected to the downstream end of a single-combustion-chamber cylinder exhaust channel section (31). A single-combustion-chamber main catalyst (39) is positioned inside the single-combustion-chamber exhaust pipe (34). The channel length from one combustion chamber (29) to the upstream end thereof is greater than the channel length from the downstream end thereof to the downstream end of the single-combustion-chamber exhaust pipe (34). At least a section extending from the downstream end of the single-combustion-chamber cylinder exhaust channel section (31) to the upstream end of the main catalyst (39) is formed by a warmth-retaining exhaust channel section (44) equipped with a warmth-retaining structure.