What shape is this Briggs Vanguard in . Troubleshoot Briggs Vanguard Engine. Lets look and test before trying to start or install Briggs and Stratton engine. DS520. The valves are not sealing , shows a picture of valve at the end. Harbor Freight leak down tester used and a DEPSTECH Triple Lens Borescope Inspection Camera DS520. After some quick testing and inspection camera i see the valves have lots of carbon on them . 3 out of 4 valves are not sealing. Can still see honing marks in the cylinders of this 18 hp briggs horizontal shaft vanguard engine. Valve inspection.