A balanced rotary engine for applying torque to a drive shaft. The engine has an outer casing with a main drive case. A cylinder is rotably mounted in the casing and a piston is mounted to move longitudinally within the cylinder. Two connecting arms, each with a connecting end, one of the ends is connected to the piston, and two crankshafts, each one being rotably connected to the other connecting end of the connecting arms. Two drive wheels are contra-rotably connected to the respective first and second crankshafts. A fixed drive ring has a circumferentially disposed drive member surface. The fixed drive ring is mounted in the case so that the drive member surface faces the piston. The two drive wheels mesh with the drive ring.

Disclosed are four-stroke internal combustion engines and engine modules. The engine modules described herein convert linear reciprocating motion of a piston within a cylinder to rotational motion of a flywheel, which rotates around the cylinder's axis, or to rotational motion of the cylinder, which rotates within the flywheel. The linear reciprocating motion of the piston causes rotation of the flywheel or cylinder by piston pins being pushed down a sloped, spiraling surface of the flywheel, resulting in highly efficient power transfer. The rotational motion is transferred through a final drive, such as a drive shaft, drive train or drive chain. Engines described herein may include pairs of engine modules.

A multi-link engine is provided with an upper link, a lower link and a control link. The upper link is pivotally connected to a piston by a piston pin. The lower link is rotatably mounted on a crankpin of a crankshaft and connected to the upper link by an upper pin. The control link is rotatably connected to the lower link by a control pin and pivotally mounted on a pivot portion of a control shaft. The links are configured and arranged with respect to each other such that inertia forces of a prescribed second or higher order in terms of an engine rotational speed act on at least the upper link and the control link in a transverse direction of the engine with a sum of leftward and rightward inertia forces of the prescribed second or higher order being substantially zero.

A multi-link engine is provided with an upper link, a lower link and a control link. The upper link is pivotally connected to a piston by a piston pin. The lower link is rotatably mounted on a crankpin of a crankshaft and connected to the upper link by an upper pin. The control link is rotatably connected to the lower link by a control pin and pivotally mounted on a pivot portion of a control shaft. The links are configured and arranged with respect to each other such that inertia forces of a prescribed second or higher order in terms of an engine rotational speed act on at least the upper link and the control link in a transverse direction of the engine with a sum of leftward and rightward inertia forces of the prescribed second or higher order being substantially zero.

A reconditioned harmonic balancer to replace a worn out or damaged harmonic balancer that is not available otherwise. The reconditioned harmonic balancer includes two or more pieces of metal held together with a cleaned hub, a cleaned inertia ring, a plurality of new elastomer material, a plurality of timing marks that need to be located on a keyway indicator at a precise location, and a plurality of mounting apertures. The timing marks are engraved, single-notched hash marks, or are painted on an outer surface of the cleaned inertia ring. The mounting apertures are disposed on the cleaned hub to secure the reconditioned harmonic balancer to a crankshaft of a vehicle.

A reconditioned harmonic balancer to replace a worn out or damaged harmonic balancer that is not available otherwise. The reconditioned harmonic balancer includes two or more pieces of metal held together with a cleaned hub, a cleaned inertia ring, a plurality of new elastomer material, a plurality of timing marks that need to be located on a keyway indicator at a precise location, and a plurality of mounting apertures. The timing marks are engraved, single-notched hash marks, or are painted on an outer surface of the cleaned inertia ring. The mounting apertures are disposed on the cleaned hub to secure the reconditioned harmonic balancer to a crankshaft of a vehicle.

A reconditioned harmonic balancer to replace a worn out or damaged harmonic balancer that is not available otherwise. The reconditioned harmonic balancer includes two or more pieces of metal held together with a cleaned hub, a cleaned inertia ring, a plurality of new elastomer material, a plurality of timing marks that need to be located on a keyway indicator at a precise location, and a plurality of mounting apertures. The timing marks are engraved, single-notched hash marks, or are painted on an outer surface of the cleaned inertia ring. The mounting apertures are disposed on the cleaned hub to secure the reconditioned harmonic balancer to a crankshaft of a vehicle.

A reconditioned harmonic balancer to replace a worn out or damaged harmonic balancer that is not available otherwise. The reconditioned harmonic balancer includes two or more pieces of metal held together with a cleaned hub, a cleaned inertia ring, a plurality of new elastomer material, a plurality of timing marks that need to be located on a keyway indicator at a precise location, and a plurality of mounting apertures. The timing marks are engraved, single-notched hash marks, or are painted on an outer surface of the cleaned inertia ring. The mounting apertures are disposed on the cleaned hub to secure the reconditioned harmonic balancer to a crankshaft of a vehicle.