A decompression device of an internal combustion engine which is arranged compactly
with reduced number of parts is provided. Typically, the device comprises a push-up
rod which is disposed on a circumference of a cam shaft of the engine, within a
range in the circumferential direction corresponding to a compression stage of
the engine, and which protrudes outwardly in the radial direction of the cam shaft
with respect to a base face of an exhaust-side cam face. The push-up rod is supported
movably in the cam shaft direction between a decompression operating position,
at which the push-up rod is inserted into a width-wise range of a bottom face of
an exhaust-side tappet and a decompression non-operating position, at which the
push-up rod is retreated from the width-wise range of the bottom face. Moreover,
in the case of a multi-cylinder internal combustion engine having two cam shafts,
a common solenoid is interlocked with the push-up rods provided on both the cam
shafts and, thus the single solenoid can decompress the cylinders.
