An engine includes a crankcase with cylinders and fins on outer circumferences of the cylinders. A crank shaft penetrates the crankcase. A cooling fan is provided on an outer side of the crankcase and arranged coaxially with the crank shaft. A first cover covers an outer side of the cylinders and the crankcase, and the cooling fan. A second cover capable of being detached from/attached to the first cover. The first cover includes a first opening facing the cooling fan, and second openings facing the fins. The second cover includes an air inlet facing the first opening, and attached to the first cover to cover the first opening and the second openings.

A first die segment for forming an internal combustion engine block has cylindrical projections, and die core pieces disposed about the cylindrical projections. A second die segment has die core stubs positioned so as to extend between adjacent die core pieces when the segments are brought together. An engine block formed by the die segments has cylindrical bores formed by the cylindrical projections extending from the deck of the block and voids formed by the die core pieces also extending from the deck and disposed about the cylindrical bores. Pockets formed by the die core stubs extend into sides of the engine block between adjacent voids. The engine block is worked below the level of the deck to undercut each of the pockets, removing material between them and the voids to result in an interconnected water jacket extending about the cylindrical bores, while leaving the deck closed.

A cover structure of an internal combustion engine of a motorcycle includes an engine that is mounted on a motorcycle and includes a cooling device for cooling the engine. The cover structure includes a sprocket cover portion that covers from the width direction of the vehicle. The cover structure also includes a pipe cover portion that covers from the width direction of vehicle a discharge side hose and an intake side hose of the cooling device. The cover structure further includes a side surface cover that includes a joining portion which is vertically arranged from the sprocket cover portion towards the pipe cover portion so as to be in parallel with the discharge side hose. The intake side hose is arranged side by side in the width direction of the vehicle and integrally joins the sprocket cover portion with the pipe cover portion.

An internal combustion engine including a base engine; a water jacket which is formed in the base engine and through which a cooling fluid can flow, a recess in a wall of the base engine which extends into the water jacket, a heat exchanger which is arranged at least partially in the recess and through which a second fluid can flow, so that thermal energy can be exchanged between the cooling fluid and the second fluid, a heat exchanger cover, via which the heat exchanger is connected to a fluid circuit through which the second fluid can flow, the heat exchanger being fastened to the heat exchanger cover and the heat exchanger cover being fastened to the base engine, and a pin which positions the heat exchanger cover, the contact section and the base engine relative to one another.

An engine includes a common rail attached to one side portion of a cylinder block that pivotally supports a crankshaft in a rotatable mariner, the one side portion extending along a crankshaft center, and the common rail being configured to supply a fuel to the engine. A flywheel housing that accommodates a flywheel that is rotated integrally with the crankshaft is disposed in one side portion out of opposite side portions of the cylinder block intersecting the one side portion. One end portion of the common rail is disposed above the flywheel housing.