An internal combustion may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The piston may be configured to move in the cylinder in a work stroke from one end to another. The work stroke may include an expansion stroke portion and a non-expansion stroke portion. The non-expansion stroke portion may include a momentum stroke portion, and a compression stroke portion. The engine may further include first and second piston rod portions extending from opposite faces of the piston. Passageways in the piston rod portions may be configured to communicate gases between a combustion chamber and other locations.

An inlet manifold arrangement is disclosed for a four-stroke internal combustion engine having at least one working cylinder with inlet valves and outlet valves and an inlet manifold assembly. The inlet manifold assembly has a flow direction for fluid (such as a fuel-air mixture) in the inlet direction, and an end section near an air filter device. The manifold assembly also has a throttle valve arrangement and a non-return valve which blocks in the direction opposite to the flow direction. The non-return valve is situated, in relation to the flow direction, between the end section of the inlet manifold assembly and the throttle valve arrangement.

A linear reciprocating engine may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The engine may further include a first piston rod portion extending from a first face of the double-faced piston through the first combustion chamber, and a second piston rod portion extending from a second face of the piston through the second combustion chamber. Passageways in the piston rod portions may be configured to communicate gases between the combustion chamber and a location outside the cylinder and configured to prevent gases from being exchanged between the cylinder and a location outside the cylinder via a path that crosses both face of the piston.

An outboard motor includes an engine main body, and an intake device to supply air to the engine main body. The intake device includes a main intake pipe including a first intake pipe and a second intake pipe connected to a downstream end of the first intake pipe and extending at an angle with respect to an axial direction of the first intake pipe and through which the air supplied to the engine main body flows, and an extension pipe extending from a connection between the first intake pipe and the second intake pipe and including a resonance chamber therein. The extension pipe includes an extended peripheral wall and an end wall that closes the resonance chamber except for a portion adjacent to the main intake pipe.

The oil filter device is disposed on a side portion of one side of a cylinder body in a width direction in a cylinder head side with respect to an engine case in a space between center lines of main lubricating oil passages and a cylinder axis line of the cylinder body, and includes an oil pump disposed on the engine case and further lubricating oil passages that connect to the main lubricating oil passage.

An engine case includes bearings, an oil pump, lubricating oil passages, and a relief device. The bearings rotatably support a crankshaft and a camshaft. The oil pump and the lubricating oil passages are configured to pressure-feed lubricating oil to the bearings. The relief device is configured to adjust a pressure of the lubricating oil. The lubricating oil passages include main lubricating oil passages. The main lubricating oil passages include communication portions linearly formed with extending portions. The communication portions communicate between the respective bearings of the crankshaft and the camshaft from outside the engine case. The extending portions extend from outside the engine case to the bearing of the camshaft. The relief device is disposed having a relief valve and a relief hole at the extending portions.

A piston is provided for an internal combustion engine. The piston may include a cylindrical first piston portion having a first diameter, a cylindrical second piston portion of the first diameter, and a cylindrical third piston portion of a second diameter less than the first diameter located between the first piston portion and the second piston portion. The first piston portion may be configured such that prior to assembly, the first piston portion is separate from the second piston portion. The piston may also include a continuous, gapless piston ring circumscribing the third piston portion, where the piston ring may be configured such that when heated the piston ring deforms in an axial direction of the piston.

A standby generator includes an engine including an output shaft, an alternator, and an enclosure including a base and a number of walls extending from the base including a front wall, a rear wall, a first wall, and a second wall. The standby generator includes an intake opening configured to allow air to be drawn into the enclosure and an exhaust opening configured to allow heated air and exhaust gases to be expelled from the enclosure. The intake opening is provided on the rear wall proximate the first wall and the exhaust opening is provided on the front wall proximate the second wall. The air drawn into the enclosure at the first intake opening directly flows over the engine and is expelled through the exhaust opening.

A marine motor assembly for mounting to a watercraft is disclosed. The marine motor assembly has a motor unit including a motor unit housing, a motor, a propulsion device, an air pump fluidly communicating with an under-housing volume of the motor unit housing, a pressure sensor for measuring air pressure in the under-housing volume, and a control unit communicating with the air pump and the pressure sensor. The control unit is programmed for controlling the air pump for changing air pressure in the under-housing volume, and monitoring change in the air pressure for a predetermined amount of time for confirming that the motor unit housing is water-resistant, or that the water resistance of the motor unit housing is compromised. A method for testing a water resistance of a motor unit housing of a marine motor assembly is also disclosed.

An inlet manifold arrangement is disclosed for a four-stroke internal combustion engine having at least one working cylinder with inlet valves and outlet valves and an inlet manifold assembly. The inlet manifold assembly has a flow direction for fluid (such as a fuel-air mixture) in the inlet direction, and an end section near an air filter device. The manifold assembly also has a throttle valve arrangement and a non-return valve which blocks in the direction opposite to the flow direction. The non-return valve is situated, in relation to the flow direction, between the end section of the inlet manifold assembly and the throttle valve arrangement.