OVERHEAD CAMSHAFT ENGINE

In an overhead cam engine (10) having a first bearing (21) supported by the cylinder block (11), and a second bearing (22) supported by a bearing retaining member (60) attached to the cylinder block inside a crankcase chamber (12) for rotatably supporting a crankshaft (20), the crankshaft is provided with a reduced diameter portion (24b) having a smaller outer diameter than an adjoining part of the crankshaft on a side of the second bearing facing away from a cylinder (15) defined in the cylinder block, and a crankshaft pulley (53) is mounted on the reduced diameter portion.