Patent ID: 7086371

Claim:
An engine having a crankshaft, a crankcase having a plurality of bearing portions for rotatably supporting said crankshaft, each of said bearing portions being dividable along a divisional plane arranged on the axis of said crankshaft, cylinder barrels connected to said crankcase, said cylinder barrels having cylinder bores with axes perpendicular to said divisional plane, and cylinder heads connected to said cylinder barrels comprising: said cylinder heads being integrated with portions of said cylinder barrels forming at least said cylinder bores to form cylinder blocks; and said cylinder blocks and said crankcase being fastened together by a plurality of fastening bolts having axes parallel to the axes of said cylinder bores and extending through at least said cylinder blocks, with a compressive structure in the axial direction of the fastening bolts; wherein the fastening bolts are arrange in equal intervals on each of upper and lower sides of the cylinder bores in a direction parallel to the axis of the crankshaft in such a manner that four of the fastening bolts surround each of the cylinder bores, wherein a pitch of the fastening bolts in the axial direction of the crankshaft is set smaller than a pitch of the fastening bolts in a vertical direction perpendicular to the axial direction of the crankshaft, and upper and lower sides of the cylinder blocks are integrally formed with a plurality of mounting bosses extending from mounting surfaces of the cylinder barrels to the crankcase to the cylinder heads.