The mower runs! Thank you so very much for your help and the motor manual. This saved me significant money!! In the end the issue was the spring on the exhaust valve. The spring broke and released the keeper followed shortly by the remaining top assembly. I could have just purchased a new spring but I went ahead replaced the worn parts on the whole assembly and the cylinder head gasket. It cost me about $100 but I could have done it for even less if I had really needed to. Thanks again for sharing your expertise.
Thank you for taking the time to report back. Most posters never let us know if the info we post is of any value or the problem was ever solved. Glad to hear you got it runnig.