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The Indian authorities have put in emission legislation norms for 2-wheelers that will result in widespread use of exhaust catalysts on 2-stroke powered vehicles by 2000. A number of 2-wheelers from the Indian market were used to examine fuelling and catalyst variables. Reducing carburetor jet size resulted in leaner operation and improved tailpipe emissions, particularly for CO. Increasing catalyst size and cell density gave emission improvements, however, higher cell densities could increase back pressure resulting in richer operation and higher CO levels. The effect of catalytic metal type and concentration was established. In addition, the important deactivation mode of ignition misfire leading to excessive catalyst temperatures was examined experimentally and this has resulted in some important guidelines for catalyst selection and extent of permissible misfire, which can improve catalyst life in service.