Dave, (Enfield, CT)
Dave, I’ve searched my technical library and I cannot find a 4.5 kW Onan from that time frame, though I could be mistaken. They did produce a 4.0 and a 5.0 at that time; each using a different engine. To the best of my knowledge, the correct gap with the points full open (TDC) should measure .020" for all engines of that era. To be sure, a quick call to any Onan distributor should confirm this. By describing the look of the engine and any other markings still on the unit, the distributor should be able to positively identify which engine is coupled to that generator.