Air-cooled single cylinder internal combustion engine, straddle-type vehicle and manufacturing method of air-cooled single cylinder internal combustion engine

摘要

A cylinder head body (100) of an air-cooled single cylinder internal combustion engine is integrally molded from an aluminum alloy by die casting, and the aluminum alloy contains Si of 8.0 wt% or more and 12.0 wt% or less, 0.5 wt% Or less of Cu, 0.002 wt% or more and 0.02 wt% or less of Sr, 0.2 wt% or more and 0.5 wt% or less of Mg, 0.5 wt% or more and 1.0 wt% or less of Fe, 0.3 wt% It contains Mn of 6 wt% or less. The thermal conductivity of the cylinder head body (100) at 100 C. is 145 W / (m K) or more, and the cylinder head body (100) has a Rockwell hardness at room temperature of 70 HRF or more and 90 HRF or less.