| 摘要 |
PROBLEM TO BE SOLVED: To prevent the abnormal abrasion of a valve seat and the inner peripheral surface of a cylinder due to the dust sucked into an engine by fitting a top plate of an air cleaning chamber to a filter at a position lower than an upper seal, and forming a screw insertion hole at a position higher than the inner bottom surface of a recessed part provided in the top plate. SOLUTION: A top plate 11 for covering an air cleaning chamber 10 from over thereof is fitted to a filter 3 at a position lower than an upper seal 7, and a recessed part 13 is provided in the top plate 11 near a screw insertion hole 12 provided in the top plate 11, and the screw insertion hole is formed at a position higher than the inner bottom surface 13a of the recessed part 13. When the dust intrudes from a part of the upper seal with the vibration during the operation, the dust are put on the top plate 11, and moved on the top plate 11 with the vibration, and fallen into the recessed part 13. The dust fallen into the recessed part 13 is hard to be moved to the screw insertion hole formed at a high position. With this structure, the dust is hard to intrude the air cleaning chamber 10, and hard to be sucked into the engine.
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