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

An object is to provide a straddled vehicle on which a single-cylinder four-stroke engine unit is mounted, which improves the purification performance of purifying exhaust gas by a catalyst and simplifying the structure of an exhauster. It is assumed that a straddled vehicle 1 is viewed in a direction of a linear line L2 which is orthogonal to a crankshaft axis Cr1 and orthogonal to a cylinder axis Cy1. The center of an upstream end 35a of a silencer 35 is provided one of leftward and rightward in a left-right direction of the center of a downstream end 31 b of a cylinder exhaust passage member 31. A main catalyst 39 is arranged so that the center of the downstream end is on the one of the leftward and rightward of the center of the upstream end. The main catalyst 39 is provided to at least partially overlap a quadrangle S10 which is formed by a side S11 which passes the downstream end 31 b of the cylinder exhaust passage member 31 and is in parallel to a cylinder axis Cy1, a side S12 which passes the downstream end 31b of the cylinder exhaust passage member 31 is in parallel to a crankshaft axis Cr1, a side S13 which passes the upstream end 35a of the silencer 35 and is in parallel to the cylinder axis Cy1, and a side S14 which passes the upstream end 35a of the silencer 35 is in parallel to the central axis of the crankshaft axis Cr1.