A piston supply apparatus includes a piston gripping portion and a piston supply portion. The piston supply portion includes a connecting rod gripping unit gripping the connecting rod of the piston placed in a preparation area, a guide member abutting against a skirt portion of the piston to match an axial direction of the piston with a predetermined specified direction, a moving unit moving the gripping unit from the preparation area to a supply position in air, and a pivoting unit making the gripping unit pivot such that the piston top portion of the piston in a downward state is set in an upward state. The piston supply apparatus further includes a pressing unit pressing the piston top portion of the piston made to pivot to the upward state against the guide member.

In a piston-ported engine, a sealing ring may be placed in a groove in the cylinder. As the groove is of greater diameter than the cylinder, the sealing ring overlaps into a helix allowing it to be enter the cylinder. However, such a helix does not fit into a groove without when in the helix. Alternatively, a shorter sealing ring is placed into the groove. However, the gap is too large. According to one embodiment, a groove of double the width of the ring is provided and the helical ring is installed and caused to unwind in the groove so that the ring sits in a plane. A spacer ring is placed in the groove to fill the extra space in the groove. An elastomeric material or a tension spring in an outer groove in the sealing ring can be used to cause the ring to press against the piston.