Abstract
This paper presents the study of LPG lean burn in a motorcycle SI engine. The lean burn limits are compared by several ways. The relation of lean burn limit with the parameters, such as engine speed, compression ratio and advance spark ignition etc. is tested. The experiment results show that the large throttle opening, low engine speed, the early of advance spark ignition, the large electrode gap and high compression ratio will enlarge the lean burn limit. The mission level of LPG engine can be significantly reduced by the means of lean burn technology, especially on NOx emission.