High concentrations of hydrocarbons in the exhaust of two-stroke Otto engines offset the advantages of their low CO and NOx emissions. The largest portion of these CH emissions are a result of combustion chamber exhaust-processes. The paper describes efforts to correct this problem.Tests were run to study experimentally the effects of various measures; testing procedures limited the number of variables. In particular, two approaches were pursued. The first, the modification of the geometry of the combustion chamber, resulted in a remarkable lowering of CH emissions; this was attributed to a partial charge-stratification and accompanying reduction in charge-formation time, achieved through the configuration of injection components. The second approach involved incorporation of direct fuel injection into the engine, and these initial efforts concentrated on overcoming irregularities in operation. On the basis of these results, it is believed that very large reductions of the CH emissions are achievable.