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Motorcycle exhaust emission standards throughout the world are becoming more stringent. Emission control systems utilizing the catalytic converter are already in production in Taiwan for 2-stroke engine motorcycles. Catalysts designed for 2-stroke engines encounter a more severe exhaust environment than do those designed for 4-stroke engines. The two aspects of increased severity are the higher temperatures and higher stresses due to engine vibrations. Precious metal catalysts have been designed to operate in the thermal environment of 2-stroke engines and such catalysts have been successfully applied to both metal and ceramic substrates. However, until now, only the metal substrate catalysts have been utilized in motorcycle application. Ceramic based catalysts have not been considered because the mounting material that holds the catalyst substrate in place did not have enough durability to withstand the thermal/vibrational forces encountered in 2-stroke engine exhaust.

In contrast to motorcycles with 4-stroke engines, 2-stroke engine motorcycles produce very high hydrocarbon and carbon monoxide emissions. Compared to a 1976 automobile, such motorcycles produce as much hydrocarbon emissions as ten to twenty passenger cars. Modified automobile catalyst technology with the addition of an air pump is shown to be effective in reducing the hydrocarbon and carbon monoxide emissions by 75 - 85% after mileage accumulation of 12,000 miles; these tests are in progress and are being continued. In spite of the fact that current 2-stroke engine motorcycles run rich (no excess air) hydrocarbon emissions can be reduced by 35% and higher with aged catalyst systems without the addition of air. The mechanical durability of the catalytic systems is completely satisfactory. Present data indicate that catalyst system technology has been developed to meet proposed interim EPA emission standards for 2-stroke motorcycle engines.