| 摘要 |
<p>A valve gear (17) comprises a camshaft (18) having valve gear cams (25, 26), first and second rocker shafts (30, 38), a first rocker arm (19) supported on the first rocker shaft (30), and a second rocker arm (20) supported on the second rocker shaft (38). The valve gear cams (25,26), respectively, comprise a cam nose (27b, 28b) projecting from a base circle (27a, 28a), and the first rocker shaft (30) supporting the first rocker arm (19) is positioned forwardly of a center line (O1), which passes through a center of the camshaft (18) to extend axially of a cylinder (4), in a direction of rotation of the camshaft (18). The first rocker shaft (30) is shifted closer to the camshaft (18) than a center (X2) of rotation of a roller bearing (34) is, when the roller bearing (34) on the first rocker arm (19) contacts with the base circle (27a) of the valve gear cam (25) .</p> |
