GRUPPO MOTOPROPULSORE CON SISTEMA DI TRASMISSIONE A CINGHIA

摘要

PROBLEM TO BE SOLVED: To cool a part close to the outside or an outer part of a crankcase by air discharged from the transmission case of a belt type transmission device to promote cooling of oil in the crank chamber.

SOLUTION: A power unit comprises: an internal combustion engine having the crankcase 2 forming a crank chamber 10 housing a crankshaft 9; the transmission case 45 forming a transmission chamber 48 housing an endless belt stretched between a drive pulley driven by the crankshaft 9 and a driven pulley 43. An air discharge port 80 is formed in a transmission case part 46 to discharge cooling air introduced in the transmission chamber 48 to the outside. A crankcase part 4 has a radial case part 4c1 positioned outside in a radial direction of a maximum rotary trajectory of the crankshaft 9 in a side view. An outlet 80b of the air discharge port 80 is opposed to a radial case part 4c1 in a discharge air flow direction at the outlet 80b.

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