| 摘要 |
PURPOSE:To prevent the blow-bye of fuel for improving thermal efficiency by forming a scavenge passage in a dual passage structure where only the upper portion of passages is communicated by a partition so that air is inducted from one passage to fill up the other passage which is communicated with a crank room. CONSTITUTION:A cylinder 1 is formed with a scavenge passage 2 having two flow paths A and B where a partition is provided for communicating them with each other by an upper section C. And a check valve 5 is provided to an air suction port 4. When a check room 7 becomes negative in pressure with a piston 6 elevated, air at atmospheric pressure flows in from a flow path A' via the flow path B toward the crank room 7. Then air from the flow path A is turned over int the upper section C for filling the flow path B' with air required for preceding a scavenge action toward the direction to the crank room 7. On the other hand, a mixture is supplied to the crank room 7 from a carburator 8 via one side 9 of the check valve 5 where a ratio of the mixture to the volume of preceding air is regulated by matching between the carburator 8 and the sluice section of the check valve 5.
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