Cooling system in a liquid cooled internal combustion engine

A cooling system for an internal combustion engine comprising

• an engine section including a cylinder head, a cylinder case and a crank case to contain a plurality of reciprocating pistons and a liquid passage for cooling the engine section by liquid flowing in the passage, said pistons being substantially vertically disposed in said engine section parallel to each other,
• pump means situated outside said crank case between two adjacent pistons, said pump means forcibly transmitting liquid into said liquid passage in said engine section to cool said engine section,
• thermostat means connected to said cylinder head above said pump means between the two adjacent pistons, said thermostat means being connected to said liquid passage in said engine section so that the liquid pumped by said pump means flows out through said thermostat means,
• a radiator connected between said thermostat means and said pump means to cool the liquid from the engine section and to supply the cooled liquid again to the engine section by means of said pump means, and
• a by-pass canal integrally formed entirely inside said engine section between said two adjacent pistons to vertically extend said engine section through said cylinder head, said cylinder case and said crank case for internally connecting said pump means and said thermostat means so that when the liquid passing through said liquid passage in the said engine section is cool, the liquid is transmitted to the pump means through said by-pass canal without passing through the radiator.