| 摘要 |
PURPOSE:To simplify a structure, by installing a drain hole in the lower part of a partition wall which partitions off a cooling water passage, guiding cooling water out of a radiator to a cylinder head from a crankcase lower part via an exhaust port, and another cooling water passage around a cylinder. CONSTITUTION:In the lower part of a crankcase 6, there is provided with a cooling water passage (a) which extends upward from a water pump discharge port, whereby cooling water is led into both cooling water passages (e) and (f) in a cylinder head 8 via the cooling water passage (b) branched off in two- step form to the side of an exhaust port 23. The cooling water passage (f) inside the cylinder head 8 is being interconnected to a cooling water passage (g) around a cylinder 17, and this cooling water passage (g) and a cooling water passage (d) are partitioned off by a thin partition wall 29. A drain hole 29 is formed in a lower part of this partition wall 29, discharging cooling water in these cooling water passages (f) and (g) when a drain plug at a water pump lower part is removed.
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