| 摘要 |
A four-stroke engine includes a case (1) which is comprised of a first case half (3) and a second case half (8) connected with each other at a parting plane which goes through centerline of a crankshaft and is perpendicular to centerline of a cylinder (7). A first bearing seat (19) is divided into a first upper bearing seat half (4) and a first lower bearing seat (9) at the parting plane. A second bearing seat (20) is divided into a second upper bearing seat half (5) and a second upper bearing seat half (10) at the parting plane. The first upper bearing seat half (4) and the second upper bearing seat half (5) are integrally molded on the first case half (3), and the first lower bearing seat half (9) and the second lower bearing seat half (10) are integrally molded on the second case half (8). An outer side surface of the first case half (3) and a side cover (21) form a valve-operating chamber (26) for receiving a valve-operating mechanism (30). |
