Motorcycle Emissions, Their Impact, and Possible Control Techniques 740627

Seven motorcycles, ranging in size from 100 to 1200 cm³, were tested for emissions characterization purposes. They were operated on the federal seven-mode test procedure (for 1971 and older light-duty vehicles), the federal LA-4 test procedure (for 1972 and later LDVs), and under a variety of steady-state conditions. Four of the machines tested had 4-stroke engines, and the other three had 2-stroke engines.

Emissions which were measured included hydrocarbons, CO, CO₂, NO, NO_x, O₂, aldehydes, light hydrocarbons, particulates, and smoke. Emissions of SO_x were estimated on the basis of fuel consumed, and evaporative hydrocarbon losses were also estimated. Crankcase “blowby” emissions from one 4-stroke machine were measured.

The impact of motorcycles on national pollutant totals was estimated, based on the test results and information from a variety of sources on national population and usage of motorcycles. In addition, a brief overview of emission control technology which might be applicable to motorcycles is presented. This discussion indicates that control of hydrocarbon emissions from 2-stroke machines and CO emissions from large motorcycles of both 2-stroke and 4-stroke types are immediate priorities for meeting the tentative 1976 EPA motorcycle emission standards.