| 摘要 |
A bolt fastening structure for an internal combustion engine includes bolt fitting holes formed in a cylinder of the engine. An inner wall of a top portion of a crankcase includes boss portions having openings, as an extension to the corresponding bolt fitting holes, with internal threads formed therein. The crankcase further includes hollow recesses formed thereon between the boss portions and crankshaft rotational support portions. Fastening bolts, each having an external thread formed at a tip portion thereof, are extended through the bolt fitting holes, and engaged with the internal threads of the boss portion. The hollow recesses include portions of the openings of the boss portions having the internal threads opened therein.
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