A water-cooled, spark-ignited, natural gas burning engine that includes an improved ignition system having a pair of precombustion chambers located in series connected by an orifice from the first chamber into the combustion chamber of the engine whereby a relatively rich fuel/air mixture, ignited in the second prechamber, propagates a flame through an orifice into the first chamber wherein a leaner fuel/air mixture from the combustion chamber is plasma ignited which in turn creates a larger flame that is projected through an orifice into the main combustion chamber for plasma igniting a lean fuel/air mixture which could not otherwise be ignited by spark ignition. The invention also contemplates a kit providing the above for use in converting water-cooled, diesel burning, compression ignited engines into water-cooled, natural gas burning, spark-ignited engines.
Michael E. Crane