A four-cycle engine typically including a crankshaft provided with a first
gear, a camshaft provided with a second gear, an endless rotation
transmission that is installed around the first and second gears and is
configured to transmit rotation of the crankshaft to the camshaft, a
crank phase detecting device configured to detect a rotational phase of
the crankshaft that is obtained by dividing a phase corresponding to one
rotation of the crankshaft by a number that is equal to or more than a
half of teeth of the second gear of the camshaft, and a cam phase
detecting device configured to detect at least one rotational phase of
the camshaft.