This paper investigates the effect of lifespan and maintenance characteristics on the CO and HC emission quality of in-used carburetor motorcycles, the research method is comparative experiments to estimate the effect of emission motorcycles before and after maintenance with different motorcycle age, AVL's Ditest gas 1000 analyzer and As one TM301 lubricant temperature equipment with K-sensor are used to measure CO, HC emissions, engine speed and lubricating oil temperature. The results of 231 in-used carburetor motorcycles showed that the concentration of CO and HC before maintenance ranged from 0.06 to 13.13% vol for CO and from 79ppm to 7350ppm for HC. After maintenance, CO and HC concentration decreased respectively from 0.04 to 10.15% vol for CO and from 47ppm to 4830ppm for HC, the average CO and HC concentrations before maintenance were 5.501% vol and 1380.730ppm, respectively. After maintenance, the average concentration of CO and HC decreased 2.794% vol and 679.592ppm respectively, the reduction of CO and HC concentration was equivalent 49.2% and 50.8%, the study results also showed that the effectiveness of reducing CO and HC concentration of motorcycles with a lifespan of more than 10 years and from 5 to 10 years are higher than those with a lifespan less than 5 years.

Keywords: Carburetor motorcycle, maintenance, age, CO and HC emission.