Two stroke gasoline engine with rotary valve enabling double acting power strokes and rotary air valve to lessen blowback

It is an object of the present invention to provide a gas driven engine having a double acting piston in a chamber that is driven in a reciprocating motion with a drive train from the piston to the power output drive shaft wherein the drive train is carried inside the piston and through the chamber wall to the power output drive shaft, at a part of the chamber wall that is covered throughout the engine cycle of operation. A piston mechanism for gas driven engines, fluid motors, pumps and the like that has a piston in a chamber that is moveable in the chamber in a reciprocating action and a rotating shaft that is driven by or drives the piston, wherein a double eccentric drive mechanically connects the piston and the drive shaft and the double eccentric drive has a minor eccentric engaged by a minor internal gear that is fixed to the inside of the piston, which converts the piston reciprocating drive motion to an orbiting axle of the minor eccentric and a major eccentric that engages a major internal gear that is fixed to the outside of the chamber and carries the output drive shaft, and the eccentrics are connected at their orbiting axles so that the major eccentric converts the orbiting motion of the minor eccentric axle to a rotational motion of the drive shaft.