A method for cleaning an exhaust valve of a two-stroke internal combustion engine is provided. The method comprises: requesting an exhaust valve cleaning cycle if at least one of a first condition or a second condition is satisfied; initiating the exhaust valve cleaning cycle if at least one of a third condition or a fourth condition is satisfied; and aborting the exhaust valve cleaning cycle if at least one of the at least one of the third or fourth conditions is no longer satisfied. The first condition is a time elapsed since a previous cleaning cycle has been completed being greater than a predetermined time. The second condition is a rate of opening of the exhaust valve being less than predetermined rate. The third condition is a throttle valve being closed. The fourth condition is an engine speed being less than a predetermined engine speed.

Control of airflow in a uniflow-scavenged, two-stroke cycle, opposed-piston engine during transient operation includes monitoring at least one operating parameter of the engine to recognize a transition to a transient state of engine operation. If a transient state of operation is detected, fuel injection and airflow into to the cylinders of the engine are controlled to optimize combustion and limit emissions. Airflow into cylinders of the engine may be controlled by increasing a scavenging ratio of the engine or by increasing a trapping efficiency of the engine.

An exhaust valve assembly for a two-stroke internal combustion engine has a valve actuator, and a two-part valve having a primary and secondary valves defining first and second decompression passages respectively. The primary valve is operatively connected to the valve actuator. The primary valve is in first, second and third primary valve positions when the valve actuator is in first, second and third actuator positions respectively. The secondary valve is in a first secondary valve position when the valve actuator is in the first or the second actuator position and in a second secondary valve position when the valve actuator is in the third actuator position. The first and second valve decompression passages fluidly communicate with each other when the valve actuator is in the second actuator position, and are fluidly separate from each other when the valve actuator is the first or the third actuator position.

An adjustable exhaust port 2-stroke motorcycle engine with a center adjustable exhaust valve or a split center adjustable exhaust valves includes a closing fork. The closing fork or closing arm base portion is screwed or bolted to a control rod shaft. At least one spring is disposed between a surface of an engine cylinder and the at least one transverse post of an exhaust valve. A first end of the at least one spring is in contact with the surface of an engine cylinder or a surface fixed mounted to the surface of the engine cylinder, and a second end of the spring is in contact with or linked to the at least one transverse post. The center adjustable exhaust valve or either or both of a split center adjustable exhaust valves is spring biased to an open position by the at least one spring at all times.

An engine system and method of operation therefor are provided. The system is a two-stroke internal combustion engine having an exhaust valve assembly that controls the exhaust cycle relative to crankshaft timing. The exhaust valve assembly is positioned between exhaust port and an exhaust pipe. The exhaust valve assembly comprises a rotary exhaust valve and valve phasing assembly. The rotary exhaust valve comprises a valve body defining a valve void therethrough. The use of the rotary exhaust valve allows for alteration or calibration of the fixed time and location at which the intake port and exhaust port are opened and closed by the piston with respect to the respective engine cycle. Notably, while still uncovered by the piston, the exhaust port may be closed due to full misalignment of the valve void and the exhaust port, while the intake port remains open, allowing for cylinder charging.

An engine system is disclosed. The engine system may have an engine including at least one cylinder. Further, the engine system may have a nozzle configured to selectively inject gaseous fuel into the at least one cylinder of the engine. The engine system may also have an intake port configured to direct air for combustion to the at least one cylinder. In addition, the engine system may have exhaust valves associated with the at least one cylinder. The exhaust valves may be configured to direct exhaust from the cylinder to an atmosphere. The exhaust valves may also be configured to close at different times.

Control of airflow in a uniflow-scavenged, two-stroke cycle, opposed-piston engine during transient operation includes monitoring at least one operating parameter of the engine to recognize a transition to a transient state of engine operation. If a transient state of operation is detected, fuel injection and airflow into to the cylinders of the engine are controlled to optimize combustion and limit emissions. Airflow into cylinders of the engine may be controlled by increasing a scavenging ratio of the engine or by increasing a trapping efficiency of the engine.

An engine system and method of operation therefor are provided. The system is a two-stroke internal combustion engine having an exhaust valve assembly that controls the exhaust cycle relative to crankshaft timing. The exhaust valve assembly is positioned between exhaust port and an exhaust pipe. The exhaust valve assembly comprises a rotary exhaust valve and valve phasing assembly. The rotary exhaust valve comprises a valve body defining a valve void therethrough. The use of the rotary exhaust valve allows for alteration or calibration of the fixed time and location at which the intake port and exhaust port are opened and closed by the piston with respect to the respective engine cycle. Notably, while still uncovered by the piston, the exhaust port may be closed due to full misalignment of the valve void and the exhaust port, while the intake port remains open, allowing for cylinder charging.

An engine system and method of operation therefor are provided. The system is a two-stroke internal combustion engine having an exhaust valve assembly that controls the exhaust cycle relative to crankshaft timing. The exhaust valve assembly is positioned between exhaust port and an exhaust pipe. The exhaust valve assembly comprises a rotary exhaust valve and valve phasing assembly. The rotary exhaust valve comprises a valve body defining a valve void therethrough. The use of the rotary exhaust valve allows for alteration or calibration of the fixed time and location at which the intake port and exhaust port are opened and closed by the piston with respect to the respective engine cycle. Notably, while still uncovered by the piston, the exhaust port may be closed due to full misalignment of the valve void and the exhaust port, while the intake port remains open, allowing for cylinder charging.

An apparatus for adjusting power and noise characteristics of an internal combustion engine comprises a wall configured to define an engine cylinder that includes a bore and a compression relief passage. A compression relief valve is configured to selectively adjust fluid flow capacity of the compression relief passage. A manifold is configured to be in fluid communication with the exhaust passage and includes an exhaust bypass valve to permit exhaust to at least partially bypass a noise suppressor. Operational characteristics of the engine can be adjusted along a range that extends from a first set of operational characteristics present when both the compression relief valve and the exhaust bypass valve are in a fully open position to a second set of operational characteristics present when both the compression relief valve and the exhaust bypass valve are in a fully closed position.