| 摘要 |
PROBLEM TO BE SOLVED: To provide a cylinder block structure of a four-cycle multi-cylinder engine having simple formation, which can control pressure fluctuations within cylinders without impairing the rigidity of a crankcase and a cylinder block. SOLUTION: In the engine 2 provided with the vertically divided type crankcase 10 including the cylinder block 12 having a water jacket 11 and an upper case 14 formed integrally with the cylinder block 12, a crankshaft 4 is arranged laterally relative to the car body advancing direction and the plural cylinders 6 are inclined toward the car body advancing direction. A communication hole 36 is extended in the direction of the cylinder arrangement within the back wall of them cylinder block 12 in the car body advancing direction. A passage 38 communicating the hole 36 to the inside of the crankcase 10 is formed in the cylinder block 12, and the hole 36 is formed near the outside of a rotational locus 40 generated by the outer end part of a crank web of the crankshaft 4.
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