Compression release mechanism and internal combustion engine including the same

A compression release mechanism comprising:

• a hollow camshaft including:
• a peripheral wall having an outer peripheral surface and an inner peripheral surface,
• a cam protruding radially outwardly from the outer peripheral surface,
• an inner space at least partially defined by the inner peripheral surface, and
• a radial opening formed in the peripheral wall so as to communicate with the inner space;
• a lever at least partially disposed in the inner space, the lever configured to rotate together with the camshaft about an axis of the camshaft;
• a support shaft extending perpendicular to the axis of the camshaft, the support shaft configured to pivotally support the lever such that the lever is further configured to switch between a first position and a second position relative to the camshaft;
• and
• a spring attached to the camshaft, the spring urging the lever toward the first position,
• wherein the lever includes:
• a cam portion configured to protrude outwardly through the opening when the lever is in the first position,
• a centrifugal weight configured to exert a centrifugal force against the spring so as to move the lever toward the second position in accordance with rotation of the camshaft, and
• an abutment portion configured to abut the inner peripheral surface when the lever is in the first position, and to separate from the inner peripheral surface as the lever moves toward the second position.