Patent ID: 8220429

Claim:
A single-cylinder four-stroke internal combustion engine arranged in an overhead valve configuration, comprising: a first valve train comprising a first cam on a camshaft; a first pushrod driven by the first cam; a first rocker arm coupled to the first pushrod; and an exhaust valve driven by the first rocker arm; a second valve train comprising a second cam on the camshaft; a second pushrod driven by the second cam; a second rocker arm coupled to the second pushrod; and an intake valve driven by the second rocker arm; wherein the first rocker arm is longer than the second rocker arm; a cylinder head having an exhaust port on a side of the cylinder head, the exhaust port configured to be coupled to a muffler, wherein the exhaust valve is closer to the exhaust port than the intake valve is to the exhaust port; and a spark plug inserted through the cylinder head, wherein the spark plug is closer to the exhaust port than the intake valve is to the exhaust port.