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Two-stroke engines are being utilized in large numbers as small utility, lawn and garden equipment engines. The following two subjects were examined with regards to exhaust emission control. The first subject was to compare the theoretical values of a combustion model simulation with the experimentally measured values of the base line emission of two-stroke volume as follows in detail. Considering high short-circuiting and residual gas characteristics peculiar to two-stroke engines, comparison analysis between measured exhaust emissions and calculated values by a thermodynamic combustion model simulation. Comparison analysis of the trapping efficiency-corrected HC, NOx, CO mass emission rates by the fuel flow and the fuel and air flow method. Analysis of influence to engine power and mass emission rates by the cylinder thermal load change with varing air-fuel ratio of the charge mixture.

The chain saw engines are single-cylinder, the vibration of the engines themselves are significant. To minimize the vibratory acceleration transmitted to the handles from this sources, an anti-vibration device is required to damp vibration suitably. This type of anti-vibration device, however, requires a rather soft spring constant and anti-vibration rubber bushings with high deformation, that is the size and bulkiness of which not only make forestry work difficult, but also dangerous. To resolve these problems it is essential to reduce the vibration acceleration as far as possible by optimizing engine balance. The two stroke cycle horizontally-opposed 2-cylin-der simultaneous-ignition engine provides the best balance for chain saw applications, and research and development was advanced on this basis. The results showed a reduction in vibration acceleration level at the engine itself to about 10% of conventional 1-cylinder chain saw engine, and reduction in the handles to about 20%.