Studies were made to determine the influence of different reaction temperatures and residence times on biodiesel yield by transesterification of karanja oil (Pongamia pinnata) in the presence of methanol using a solid acid heterogeneous catalyst in a continuous process. Recycle runs were conducted by further transesterification of the organic phases (first run mixture of methyl ester and unconverted oil) in the presence of methanol under similar conditions. High-pressure liquid chromatography (HPLC) reveals poor biodiesel yield even with an increase in the reaction temperature and residence time in the first run. Biodiesel yield obtained from the recycle runs, however, was greatly increased over that of the first-run biodiesel yield. Recycle transesterification at a reaction temperature of 240 degrees C and residence time of 50min gives a maximum yield value of 97.74%. Consequently, irrespective of the presence of high free fatty acids and other impurities in karanja oil, recycling the organic phase of the first run significantly enhances the biodiesel yield.