García Gómez, Jorge Alberto2012-04-272012-04-2720061909-0455http://hdl.handle.net/10567/214Introduction. The Metropolitan Area of the Aburrá Valley, as an environmental urban authority, made in the end of 2005 and the beginning of 2006 a campaign of vehicle emissions generated by motorcycles with two and four stroke engines. Such vehicles are not regulated by the national environmental laws and their impact on the air quality is really significant. This is done as a part of the Metropolitan Area of the Aburrá Valley´s mobile sources program. Objective. Collect information to contribute with the Ministry of Environment, Living and Territorial Development on the generation of technical data to determine the allowed emissions limit for the motorcycles commercialized in the country. Materials and methods. To make this study service centres and assemblers were hired to synchronize motorcycles with our emission monitoring unit. Then, the motorcycles were verified before and after the operation. 550 two and four stroke motorcycles were analyzed, and this equals 1100 gases emissions data before and after the synchronization. Results. The results of the campaign were sent to national authorities like IDEAM and the Ministry of Environment, Living and Territorial Development, to serve as a technical basis in the formulation of emission norms for motorcycles. Conclusion: Synchronizing the engines of motorcycles contributes to diminish their contaminant emissions. In four stroke engines, for instance, the reduction of CO can reach a 37% rate.esMonóxido de carbonoCorporación Universitaria LasallistaÁrea Metropolitana del Valle de AburráMotocicletasEmisión de gases vehicularesContaminación del aireContaminación del aire - MedellínArticle