This paper deals with a research project concerning an effective utilization of exhaust gas heat. Exhaust gas from a exhaust gas-separate type two-stroke cycle engine containing a high concentration of unburned gas was temporarily stored in a floating-bell type tank as an form of heat energy conservation, while in the previous report * exhaust heat was recovered with continuous operation. A Stirling engine with a hot-water supply system was then used to oxidize or burn again the exhaust gas in a catalyzer and an after-burner unit in order to recover the unspent heat energy from the exhaust gas. A three-way catalyzer was employed to remove pollutants both from the combustion gas in this process and the high-concentration burned gas from the two-stroke cycle engine.The results of the research in the present paper are intended as a follow-up of the previous report  to clarify a method for the more effective use of exhaust gas heat. Similarly to the results presented in the previous paper the present follow-up report establishes a method for the nearly complete removal of the pollutants CO and HC from emission gas at a fuel lean range of air-fuel ratio. The method significantly reduces the NO content of the gas at the same air-fuel ratio. It should also be noted that utilizing the Zeldovich reaction mechanism increases the ability to verify NO formation characteristics in the emission gas for measured results. The previous paper had reported that the bimolecular reaction mechanism also served to study the formation characteristics of NO in the process.