Abstract: An engine assembly for a vehicle includes an internal combustion engine and an exhaust system. The exhaust system includes a catalytic converter, a main muffler, a hydrocarbon trap, a pre-muffler disposed upstream from the main muffler and the hydrocarbon trap, and an exhaust path valve. The exhaust path valve is movable between first and second exhaust path positions. The exhaust path valve obstructs a second exhaust path in the first exhaust path position such that exhaust gas flows from an exhaust port of an engine cylinder to the catalytic converter to the main muffler and to the atmosphere. The exhaust path valve obstructs a first exhaust path in the second exhaust path position such that exhaust gas flows from the exhaust port of the engine cylinder to the catalytic converter to the hydrocarbon trap and to the atmosphere.

Abstract: A method of operating an exhaust valve of a two-stroke internal combustion engine is disclosed. The engine has a cylinder and a piston movably disposed within the cylinder. The cylinder defines at least one exhaust port for discharging exhaust fluid from the cylinder. The exhaust valve is configured to cyclically obstruct the exhaust port. The method includes: rotating the exhaust valve in a first direction for clearing the exhaust port before the piston uncovers the exhaust port during a downstroke of the piston, the first direction being opposite a direction of rotation of a crankshaft of the engine; and rotating the exhaust valve in the first direction for at least partially closing the exhaust port before the piston fully covers the exhaust port during an upstroke of the piston, said rotating of the exhaust valve relative to the rotation of the crankshaft at least partially counterbalancing the crankshaft.

Abstract: An engine assembly for a vehicle includes an internal combustion engine operating on a two-stroke engine cycle. A compressor is in fluid communication with an intake port of at least one cylinder of the engine to pump air into the engine. An exhaust pipe is in fluid communication with an exhaust port of the at least one cylinder. The exhaust pipe has an inlet and an outlet defining a length of the exhaust pipe therebetween. A diameter of the exhaust pipe increases along a portion of the length of the exhaust pipe in a flow direction of the exhaust pipe. The diameter of the exhaust pipe does not decrease along the length of the exhaust pipe in the flow direction of the exhaust pipe.

Abstract: An engine assembly for a vehicle includes an internal combustion engine operating on a two-stroke engine cycle. A compressor is in fluid communication with an intake port of at least one cylinder of the engine to pump air into the engine. An exhaust pipe is in fluid communication with an exhaust port of the at least one cylinder. The exhaust pipe has an inlet and an outlet defining a length of the exhaust pipe therebetween. A diameter of the exhaust pipe increases along a portion of the length of the exhaust pipe in a flow direction of the exhaust pipe. The diameter of the exhaust pipe does not decrease along the length of the exhaust pipe in the flow direction of the exhaust pipe.

Abstract: A method of operating an exhaust valve of a two-stroke internal combustion engine is disclosed. The engine has a cylinder and a piston movably disposed within the cylinder. The cylinder defines at least one exhaust port for discharging exhaust fluid from the cylinder. The exhaust valve is configured to cyclically obstruct the exhaust port. The method includes: rotating the exhaust valve in a first direction for clearing the exhaust port before the piston uncovers the exhaust port during a downstroke of the piston, the first direction being opposite a direction of rotation of a crankshaft of the engine; and rotating the exhaust valve in the first direction for at least partially closing the exhaust port before the piston fully covers the exhaust port during an upstroke of the piston, said rotating of the exhaust valve relative to the rotation of the crankshaft at least partially counterbalancing the crankshaft.

Abstract: A two-stroke internal combustion engine has a crankshaft disposed at least in part in a crankcase, and a cylinder block connected to the crankcase and defining a cylinder. The cylinder defines at least one exhaust port for discharging exhaust fluid. A piston is movably disposed within the cylinder and is operatively connected to the crankshaft. The piston is movable along a cylinder axis in a reciprocating motion including an upstroke and a downstroke. An exhaust valve assembly is operatively connected to and rotates with the crankshaft. The exhaust valve assembly has a shaft rotatably supported by the cylinder block and a valve configured to cyclically obstruct the exhaust port. The valve is operable to move clear of the exhaust port before the piston uncovers the exhaust port during its downstroke, and at least partially close the exhaust port before the piston fully covers the exhaust port during its upstroke.

Abstract: A two-stroke internal combustion engine has a crankshaft disposed at least in part in a crankcase, and a cylinder block connected to the crankcase and defining a cylinder. The cylinder defines at least one exhaust port for discharging exhaust fluid. A piston is movably disposed within the cylinder and is operatively connected to the crankshaft. The piston is movable along a cylinder axis in a reciprocating motion including an upstroke and a downstroke. An exhaust valve assembly is operatively connected to and rotates with the crankshaft. The exhaust valve assembly has a shaft rotatably supported by the cylinder block and a valve configured to cyclically obstruct the exhaust port. The valve is operable to move clear of the exhaust port before the piston uncovers the exhaust port during its downstroke, and at least partially close the exhaust port before the piston fully covers the exhaust port during its upstroke.

Abstract: 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.

Abstract: 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.

Abstract: An exhaust valve assembly has a valve actuator, a first valve part (FVP) operatively connected to the actuator, a second valve part (SVP), and at least one auxiliary valve operatively connected to the second valve part. When the actuator is in a first position, the FVP is in a fourth position, the SVP is in a seventh position and the at least one auxiliary valve is in a ninth position. When the actuator is in a second position, the FVP is in a fifth position, the SVP is in the seventh position and the at least one auxiliary valve is in the ninth position. When the actuator is in a third position, the FVP is in a sixth position, the SVP is in an eighth position and the at least one auxiliary valve is in a tenth position. The second position is intermediate the first and third positions.

Abstract: An exhaust valve assembly for a two-stroke internal combustion engine has a valve actuator having a first pressure chamber and a second pressure chamber, and a valve operatively connected to the valve actuator. The first and second pressure chambers are adapted for selectively receiving one of a first pressure and a second pressure. The first pressure is higher than the second pressure. The valve actuator moves the valve between at least a first valve position and a second valve position. The valve actuator moves the valve to the first valve position when the first pressure is supplied to the first pressure chamber and the second pressure is supplied to the second pressure chamber. The valve actuator moves the valve to the second valve position when the second pressure is supplied to the first pressure chamber and the first pressure is supplied to the second pressure chamber.

Abstract: An exhaust valve assembly for a two-stroke internal combustion engine has a valve actuator having a first pressure chamber and a second pressure chamber, and a valve operatively connected to the valve actuator. The first and second pressure chambers are adapted for selectively receiving one of a first pressure and a second pressure. The first pressure is higher than the second pressure. The valve actuator moves the valve between at least a first valve position and a second valve position. The valve actuator moves the valve to the first valve position when the first pressure is supplied to the first pressure chamber and the second pressure is supplied to the second pressure chamber. The valve actuator moves the valve to the second valve position when the second pressure is supplied to the first pressure chamber and the first pressure is supplied to the second pressure chamber.

Abstract: An exhaust valve assembly has a valve actuator, a first valve part (FVP) operatively connected to the actuator, a second valve part (SVP), and at least one auxiliary valve operatively connected to the second valve part. When the actuator is in a first position, the FVP is in a fourth position, the SVP is in a seventh position and the at least one auxiliary valve is in a ninth position. When the actuator is in a second position, the FVP is in a fifth position, the SVP is in the seventh position and the at least one auxiliary valve is in the ninth position. When the actuator is in a third position, the FVP is in a sixth position, the SVP is in an eighth position and the at least one auxiliary valve is in a tenth position. The second position is intermediate the first and third positions.