Willie, I have a 5 year old mower with a 17.5 briggs in it. I have just went thru heck and back with it. I had to put a new cam in it. The lobes on the cam were almost round instead of oblong which I was told is a common problem, engine would back fire back up thru carburator,after replacing cam I then adjusted valves to .006. Pull the valve cover off thier is two adjustments, there is a torx screw head loosen this first then adjust nut to desired tolerance, may take a couple of times when you retighten torx screw it tightens rocker up a little bit. Before adjusting pull sparkplug turn motor 1/4 inch past top dead center and its pretty simple once you do it. Good Luck Terry
terry, July 2008
