This paper discussed the results of the exhaust emission (HC, CO & Smoke) and lubricity of two stroke engines for motocycles. Three different displacements 150c.c., 125c.c. and 49c.c. air cooled type, two stroke engines were employed in this study.Results showed that the emission of HC and CO were not significantly changed by varying oil/fuel ratio, but the visible smoke could be reduced by leaner oil/fuel ratio. The HC and CO emission and visible smoke were reduced in the polybutene containing oils. Higher molecular weight polybutene were more effective for the reduction of smoke.In view of the lubricity performances, it was found that higher molecular weight polybutene caused the piston skirt scuffing and spark plug fouling problems, and also had a negative effect on piston cleanliness. The combination of low ash type additives with some ashless dispersants improved engine cleanliness and ring sticking.