Abstract: The present invention is applicable to wobble piston compressors having overrun intake ports and being driven by a motor of low starting torque. In such a layout the vacuum created in the compression chamber upon initial motion of the piston from top standstill (at the outer end of the cylinder) may be great enough to stall the motor of low horsepower. The present invention provides an overrun relief port which, although it slightly lowers the overall efficiency of the unit, provides means for breaking the initial vacuum that tends to stall the motor on starting, and it provides that service, at a low cost, and with exceptional reliability. The loss in efficiency caused by the starting relief port, or ports, is minimized by locating the said port or ports at a point where the loss in efficiency on the compression upstroke is minimized. Small capacity air compressors of the rocking rod piston--wobble piston--type when driven by low powered A.C.