An internal combustion engine comprising: a cylinder block having at least one cylinder bore defined by a cylinder wall, the cylinder block comprising, a piston reciprocating in said cylinder bore to drive a crankshaft; a plurality of transfer ports provided annularly in the cylinder wall along a periphery of the cylinder wall; and a cylinder head mounted on the cylinder block, the cylinder head comprising: at least one inlet port; at least one exhaust port; an inlet valve provided at the inlet port to regulate an opening and closing of the inlet port; an exhaust valve provided at the outlet port to regulate an opening and closing of the exhaust port; an inlet valve seat provided at the inlet port for resting the inlet valve; an exhaust valve seat provided at the exhaust port for resting the exhaust valve; characterized by an inlet valve seat rim provided at the inlet valve seat to allow delay opening and to advance closing of the inlet port; and an exhaust valve seat rim provided at the exhaust valve seat to allow delay opening and advance closing of the exhaust port, and wherein a maximum valve lift of the inlet valve from the inlet valve seat occurs during the movement of the piston from a bottom dead centre position to a top dead centre position at about 120 to 125 degrees of rotation of the crankshaft after the botttom dead centre position, wherein a maximum valve lift of the exhaust valve from the exhaust valve seat occurs during the movement of the piston from the bottom dead centre position to the top dead centre position at about 20 to 30 degrees of rotation of the crankshaft after the bottom dead centre position, and wherein the piston uncovers the plurality of transfer ports to induct the scavenging fluid at about 130 to 150 degrees of rotation of the crankshaft after the top dead centre position and covers the plurality of transfer ports at about 210 to 230 degrees of rotation of the crankshaft after the top dead centre position, wherein the inlet valve remains closed while the plurality of transfer ports is open. a cylinder block having at least one cylinder bore defined by a cylinder wall, the cylinder block comprising, a piston reciprocating in said cylinder bore to drive a crankshaft; a plurality of transfer ports provided annularly in the cylinder wall along a periphery of the cylinder wall; and a cylinder head mounted on the cylinder block, the cylinder head comprising: at least one inlet port; at least one exhaust port; an inlet valve provided at the inlet port to regulate an opening and closing of the inlet port; an exhaust valve provided at the outlet port to regulate an opening and closing of the exhaust port; an inlet valve seat provided at the inlet port for resting the inlet valve; an exhaust valve seat provided at the exhaust port for resting the exhaust valve; characterized by an inlet valve seat rim provided at the inlet valve seat to allow delay opening and to advance closing of the inlet port; and an exhaust valve seat rim provided at the exhaust valve seat to allow delay opening and advance closing of the exhaust port, and wherein at least one inlet port; at least one exhaust port; an inlet valve provided at the inlet port to regulate an opening and closing of the inlet port; an exhaust valve provided at the outlet port to regulate an opening and closing of the exhaust port; an inlet valve seat provided at the inlet port for resting the inlet valve; an exhaust valve seat provided at the exhaust port for resting the exhaust valve; characterized by an inlet valve seat rim provided at the inlet valve seat to allow delay opening and to advance closing of the inlet port; and an exhaust valve seat rim provided at the exhaust valve seat to allow delay opening and advance closing of the exhaust port, and wherein a maximum valve lift of the inlet valve from the inlet valve seat occurs during the movement of the piston from a bottom dead centre position to a top dead centre position at about 120 to 125 degrees of rotation of the crankshaft after the botttom dead centre position, wherein a maximum valve lift of the exhaust valve from the exhaust valve seat occurs during the movement of the piston from the bottom dead centre position to the top dead centre position at about 20 to 30 degrees of rotation of the crankshaft after the bottom dead centre position, and wherein the piston uncovers the plurality of transfer ports to induct the scavenging fluid at about 130 to 150 degrees of rotation of the crankshaft after the top dead centre position and covers the plurality of transfer ports at about 210 to 230 degrees of rotation of the crankshaft after the top dead centre position, wherein the inlet valve remains closed while the plurality of transfer ports is open.