Compression testing is not all that good a diagnostic tool on side valve Briggs engines, Mick, because of a patented Briggs feature called EasySpin. This holds the intake valve very slightly open during the entire compression stroke, believe it or not. Briggs therefore recommends that you assess compression on those engines by turning the engine backwards with spark plug lead disconnected of course until you find compression, then flipping the engine backwards against that compression, and observing whether it stops rotating then bounces back. A decent bounce-back is treated as evidence of satisfactory compression. Those who are inclined toward more elaborate techniques can do a leakage test instead, with the engine just past top dead center on the compression stroke, so that both valves are completely closed. This test can be rather effective, provided you have the equipment to do it, and the knowledge to interpret the results.
Some people do perform compression tests on these engines, but the result is sensitive to just how fast you spin the engine, because of EasySpin.
