Intake and exhaust apparatus for four-stroke internal-combustion engine

An intake and exhaust device of a 4-stroke internal combustion engine, comprising:

• a cylinder block for generating a rotational driving force in cooperation with the rotation of a crank shaft as an up and down reciprocating movement of a piston is transferred thereto with the aid of a connecting rod;
• a cylinder head which is engaged to an upper side of the cylinder block, with a first intake manifold opened and closed by means of a first intake and exhaust valve being connected to one side of the cylinder head, with a second intake and exhaust manifold opened and closed by means of a second intake and exhaust valve being connected to the other side of the cylinder head;
• a first cam shaft which is installed at an upper side of the cylinder head and rotates in cooperation with the rotation of the crank shaft with a first intake and exhaust cam, which drives the first intake and exhaust valve, being engaged to the first cam shaft;
• a second camp shaft which is installed at an upper side of the cylinder and rotates in cooperation with the rotation of the crank shaft with a second intake and exhaust cam, which drives a second intake and exhaust valve, being engaged to the second cam shaft;
• a third cam shaft which is installed at an upper side of the cylinder head and rotates in cooperation with the rotation of the second cam shaft;
• a first intake and exhaust adjusting means which is installed at the first intake and exhaust manifold for thereby selectively adjusting either an intake of a mixed fuel or air or an exhaust of combustion gas;
• a second intake and exhaust adjusting means which is installed at the second intake and exhaust manifold for thereby selectively adjusting either an intake of a mixed fuel or air or an exhaust of a combustion gas;
• and
• an exhaust connection pipe which communicates with the first intake and exhaust manifold and the second intake and exhaust manifold, respectively, and forms an exhaust passage of a combustion gas.