Patent ID: 7146806

Claim:
A two cycle internal combustion engine cylinder having a piston chamber comprising: an inlet port; transfer ports; an exhaust port divided into at least two sections, wherein a first one of the sections has an aperture at the piston chamber with a top surface located closer to a top of the piston chamber than a top surface of an aperture of a second one of the sections at the piston chamber, wherein the first section has a cross-sectional area which is smaller than a cross-sectional area of the second section, and wherein the aperture into the first section is located further away from the transfer ports than the aperture into the second section; and a muffler connected to the cylinder, the muffler comprising at least two exhaust gas paths connected to respective ones of the exhaust port sections, a first one of the paths comprising a catalyst and a second one of the paths not comprising a catalyst, such that a portion of the exhaust flowing through the muffler does not flow past the catalyst.