The present paper reports on measurements of particles emitted by a 6.3 kW, single cylinder two-stroke engine. The engine exhaust gas was diluted in a mini-dilution tunnel. Particle size classification was performed by means of a Differential Mobility Particle Sizer (DMPS) system. Measurements of the number distribution of the particle diameter and the related mass concentration were made under different engine operating conditions. It was found that the use of neither mineral nor synthetic lubrication oil had any influence on the emission characteristics of the engine. On the contrary: a considerable decrease in the particle number distribution was obtained by reducing the mixing ratio of lubrication oil and fuel. Also, the impact of an electrostatic precipitator was tested behind the engine's silencer. It could be shown that a significant reduction of particle emission was obtained by removing nearly all naturally charged particles from the exhaust gas.