An engine for a motorcycle comprising: a crankcase having a sidewall in which a first attachment hole is formed; a crankshaft supported by the crankcase; a cover member having a second attachment hole and provided at part of the sidewall; an oil flow path that leads oil to the first attachment hole in the crankcase; a first metal pipe having first and second end portions; and a second metal pipe having third and fourth end portions, wherein a first flange portion is provided at the second end portion of the first metal pipe, a second flange portion is provided at the fourth end portion of the second metal pipe, the first attachment hole and the second attachment hole are directed in different directions, the first end portion of the first metal pipe is inserted into the first attachment hole from outside of the crankcase, and the third end portion of the second metal pipe is inserted into the second attachment hole from outside of the crankcase, an end surface of the first flange portion and an end surface of the second flange portion are joined to each other such that the second end portion of the first metal pipe and the fourth end portion of the second metal pipe are coupled to each other, the crankshaft has an end surface opposite to the cover member, an axis flow path having an end opening at the end surface is formed inside of the crankshaft, and the end opening is arranged such that oil led from the second attachment hole is injected into the end opening, and the first flange portion of the first metal pipe and the second flange portion of the second metal pipe are fixed to the sidewall of the crankcase by means other than via the first end portion of the first metal pipe or the third end portion of the second metal pipe. a crankcase having a sidewall in which a first attachment hole is formed; a crankshaft supported by the crankcase; a cover member having a second attachment hole and provided at part of the sidewall; an oil flow path that leads oil to the first attachment hole in the crankcase; a first metal pipe having first and second end portions; and a second metal pipe having third and fourth end portions, wherein a first flange portion is provided at the second end portion of the first metal pipe, a second flange portion is provided at the fourth end portion of the second metal pipe, the first attachment hole and the second attachment hole are directed in different directions, the first end portion of the first metal pipe is inserted into the first attachment hole from outside of the crankcase, and the third end portion of the second metal pipe is inserted into the second attachment hole from outside of the crankcase, an end surface of the first flange portion and an end surface of the second flange portion are joined to each other such that the second end portion of the first metal pipe and the fourth end portion of the second metal pipe are coupled to each other, the crankshaft has an end surface opposite to the cover member, an axis flow path having an end opening at the end surface is formed inside of the crankshaft, and the end opening is arranged such that oil led from the second attachment hole is injected into the end opening, and the first flange portion of the first metal pipe and the second flange portion of the second metal pipe are fixed to the sidewall of the crankcase by means other than via the first end portion of the first metal pipe or the third end portion of the second metal pipe.