Patent ID: 7789077

Claim:
A crankcase including a lower part having an oil pan integrated with an internal combustion engine, comprising: a crankcase cover having a portion extending laterally between right and left sides of the crankcase and covering a portion of the lower part of the crankcase in which the oil pan is provided; and a space provided between the lower part of the crankcase covered by the crankcase cover and the crankcase cover, said space providing a cooling fluid passage which is in communication with a cooling fluid which circulates to cool a cylinder or a cylinder head, the cooling fluid passage being connected to a radiator and the cooling fluid including water, and wherein at a lower part of the crankcase, the portion of the crankcase cover extending laterally between right and left sides of the engine extends laterally under at least a portion of the oil pan, and further comprising a thermostat for sensing a temperature of the cooling fluid circulating in the cooling fluid passage, wherein the thermostat controls the cooling fluid in the space to prevent diluting a lubricating oil in the oil pan during warming up of the engine, and controls the cooling fluid in the space to avoid an excessive rise of the temperature of the lubricating oil in the oil pan after warming up of the engine.