Patent ID: 8276553

Claim:
A water pump attachment structure for a water-cooled internal combustion engine, in which a valve train having a camshaft disposed on a cylinder head is provided so as to be covered by a cylinder head cover comprising: a water pump having a pump drive shaft directly driven by the camshaft is disposed across a mating surface of the cylinder head and a mating surface of the cylinder head cover, wherein the cylinder head has a sidewall formed with a semicircular cut-away surface resulting from cutting away the mating surface with the cylinder head cover in a semicircle, and has screw boss portions having screw through-holes passing through the mating surface, the screw boss portions being formed on both sides of the semicircular cut-away surface, a water pump holder, formed with a semicircular cut-away surface symmetrically opposed to the semicircular cut-away surface of the cylinder head, and with internal thread holes in the mating surface with the cylinder head so as to correspond to the respective screw through-holes, forms a water pump support circular hole by allowing a semicircular cut-away surface thereof to face the semicircular cut-away surface of the cylinder head, and screw members are passed through the respective screw through-holes of the cylinder head and are threadedly engaged with the respective internal thread holes of the water pump holder for fastening the water pump holder to the cylinder head, a water pump is fitted into and secured to the water pump support circular hole, and the mating surface of the cylinder head cover conforms to the mating surface of the cylinder head and is attached to the cylinder head with the water pump holder liquid-tightly sandwiched therebetween.