I know what you mean. Machine shops that work on small engines are becoming a thing of the pass. This is the reason I said try to clean it. As for myself I just never had luck in doing so. But also I have never tryed it with the acid. Give it a try because I can't see any big money lose other then your own labor. If it was my own mower not a customers I sure woud give it a try. Have you given used parts or a used engine a thought. We are very lucky to have some very good mower salvage yards around us and I have had good luck with them.