A two-stroke internal combustion engine comprising: a crankcase ; a crankshaft disposed at least in part in the crankcase; a cylinder block connected to the crankcase; a cylinder defined in the cylinder block and having a cylinder axis , the cylinder defining at least one exhaust port for discharging exhaust fluid from the cylinder; a piston movably disposed within the cylinder and being operatively connected to the crankshaft, the piston being movable along the cylinder axis in a reciprocating motion including an upstroke and a downstroke; and an exhaust valve assembly operatively connected to and rotatable with the crankshaft, the exhaust valve assembly comprising: a shaft rotatably supported by the cylinder block and extending along a central axis ; and a valve connected to the shaft and configured to cyclically obstruct the exhaust port, the valve being operable to: move clear of the exhaust port before the piston uncovers the exhaust port during the downstroke of the piston, and at least partially close the exhaust port before the piston fully covers the exhaust port during the upstroke of the piston, the engine being characterized in that : the shaft is discontinuous; and the valve is disposed between a first portion and a second portion of the shaft such that the valve separates the first portion from the second portion. a crankcase ; a crankshaft disposed at least in part in the crankcase; a cylinder block connected to the crankcase; a cylinder defined in the cylinder block and having a cylinder axis , the cylinder defining at least one exhaust port for discharging exhaust fluid from the cylinder; a piston movably disposed within the cylinder and being operatively connected to the crankshaft, the piston being movable along the cylinder axis in a reciprocating motion including an upstroke and a downstroke; and an exhaust valve assembly operatively connected to and rotatable with the crankshaft, the exhaust valve assembly comprising: a shaft rotatably supported by the cylinder block and extending along a central axis ; and a valve connected to the shaft and configured to cyclically obstruct the exhaust port, the valve being operable to: move clear of the exhaust port before the piston uncovers the exhaust port during the downstroke of the piston, and at least partially close the exhaust port before the piston fully covers the exhaust port during the upstroke of the piston, a shaft rotatably supported by the cylinder block and extending along a central axis ; and a valve connected to the shaft and configured to cyclically obstruct the exhaust port, the valve being operable to: move clear of the exhaust port before the piston uncovers the exhaust port during the downstroke of the piston, and at least partially close the exhaust port before the piston fully covers move clear of the exhaust port before the piston uncovers the exhaust port during the downstroke of the piston, and at least partially close the exhaust port before the piston fully covers the exhaust port during the upstroke of the piston, the engine being characterized in that : the shaft is discontinuous; and the valve is disposed between a first portion and a second portion of the shaft such that the valve separates the first portion from the second portion. the shaft is discontinuous; and the valve is disposed between a first portion and a second portion of the shaft such that the valve separates the first portion from the second portion. <EOS>