| 摘要 |
An engine is provided to make a piston stroke long by increase a rotational diameter of a crank pin since a large end part does not interfere with left and right ribs. An engine includes a crank case(1), an oil pan(3), a pair of oil passages(7,8), and left and right ribs(12,13). A bottom opening portion(2) is formed in the crank case. The oil pan covers the bottom opening portion from the lower side of the crank case. The left and right oil passages are extended along left and right walls(5,6) of the crank case. The left and right ribs are extended from the left and right walls at the bottom opening portion of the crank case. The left and right oil passages are positioned inside the left and right ribs.
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