gr8flyer55, What a guy. Thanks for the offer but I just figured out the problem a few hours ago. I borrowed another mechanical advance C&H Ignition from another plane I have and the engine runs flawlessly again. I'm going to try replacing the Bosch cap with a new one I have on hand and rewire the battery leads and see if I can get the old (silver case) one to function as it should again. If not , I may have to convert to a fixed timing RCexl unit and modify my engine/timing ring to accept it. I do like the C&H mechanical timing setup though. Worked great for years and years!