Abstract: A radial piston and cylinder compressed gas motor is disclosed which is particularly suited for use where economical power sources are required. The motor includes a cylinder block having a plurality of radially extending cylinders open at their outer ends to radially extending passages and having exhaust ports open when associated pistons are adjacent their bottom dead center positions. Such passages extend to a valve system provided on the crank of the motor which functions to supply compressed gas to selected cylinders while connecting other cylinders together so that gas is exhausted from cylinders containing extending pistons to open exhaust ports in other cylinders. This minimizes back pressure to resist motor operation. The crank is formed of two generally cylindrical members and can be produced without eccentric machining or grinding operations.