A new type of variable-stroke engine, or compressor, is presented in this paper. The stroke is adjusted by changing the length of the ground link using an auxiliary mechanism. Adjusting the ground link, changes the rotation angle and the effective length of the connecting rod, which in turn controls the pumping volume of the engine. The pumping action is caused by the motion of the piston which oscillates relative to the frame as the input crank rotates through a complete cycle. The motion of the piston induces a transverse force and a bending moment in the connecting rod but no axial force or static buckling load. Since swirl combustion is known to improve thermal efficiency, this variable-stroke engine was designed to induce high swirl rates. It is believed that this type of variable-stroke engine has not previously appeared in the literature and so a complete kinematic and dynamic force analysis is included in the paper.