Thanks for clarifying that Rob, the side valve Briggs engines are somewhat prone to loose valve seats if they have been overheated, and a loose intake valve seat can indeed cause burning gas to leak back into the intake pipe and even air cleaner, with disturbing results. A tight tappet or leaky valve can have the same result. Also, your Kohler sounds as if it had a tight exhaust tappet until you adjusted it correctly. I haven't heard of that engine being as prone to wearing out its decompressor as the large Briggs OHV engines are though, which makes regular tappet adjustment on the Briggs absolutely essential. Many, many people replace Briggs starter motors and batteries, sometimes repeatedly, before they find out what the real problem is and adjust the tappets. As the Briggs decompressor wears down, tappet adjustment becomes more and more critical, until even with the minimum specified clearance, the decompressor does not work and the camshaft has to be replaced.
