I've heard that the OHV Briggs are useless as the ACR breaks on the cam and that's what the above video shows
It's just this thread says flathead (side valve) and I thought the decomp was build into the cam lobe on these motors ,I haven't needed to take one apart for a few years now. I think I have one in parts somewhere I may have a look at the last of the side valve 13 hp motors to see if they changed the cam decomp.