Abstract: 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.

Abstract: 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.

Abstract: A cylinder is configured for use with a piston that moves through compression and combustion strokes between top and bottom positions in an internal combustion engine. The cylinder defines a bore in which the piston moves between the top and bottom positions. The bore has a transfer port and an exhaust port. The cylinder can have interconnected parts that together define the bore. Those parts can include a first part that reaches along the bore upward from the transfer port beside the top position of the piston, and a second part that reaches along the bore downward from the transfer port beside the bottom position of the piston. The sectional lengths of the first and second parts provide greater access for manufacturing at the bore, the transfer port, and the exhaust port.