DOHC-type internal combustion engine

A DOHC-type internal combustion engine, comprising:

• an engine body comprising a cylinder head in which an intake-side camshaft and an exhaust-side camshaft are disposed in parallel to each other with a plug hole interposed therebetween,
• an ignition plug to be inserted into the plug hole,
• a pair of intake valves and a pair of exhaust valves disposed around the plug hole, said intake valves being arrayed in a direction along an axis of the intake-side camshaft, said exhaust valves being arrayed in a direction along an axis of the exhaust-side camshaft,
• two pairs of rocker arms respectively interposed between the intake-side and exhaust-side camshafts and said intake valves and said exhaust valves, the two pairs of rocker arms respectively corresponding to said intake valves and said exhaust valves while respectively including support portions and valve connection portions, the support portions being rockably supported by the cylinder head, the valve connection portions being operatively connected respectively with said intake valves and said exhaust valves,
• wherein first and second support portions of a first pair of the two pairs of rocker arms out of the support portions are disposed between the pair of intake valves and the pair of exhaust valves in a direction orthogonal to the axes of the intake-side and exhaust-side camshafts and around the plug hole, and
• third and fourth support portions of a second pair of the two pairs of rocker arms out of the support portions are disposed outside a region between the pair of intake valves and the pair of exhaust valves in the direction orthogonal to the axes of the intake-side and exhaust-side camshafts,
• wherein a distance between first and second valve connection portions of the first pair of the two pairs of rocker arms is set shorter than a distance between the first and second support portions, and wherein a distance between third and fourth valve connection portions of the second pair of the two pairs of rocker arms is set longer than a distance between the third and fourth support portions.