I have two mowers with the same problem. 27 horse power briggs and stratton. It just stopped running when cutting deep grass. When trying to restart it, its pops through the intake. If it starts it pops loud, no power. The 22 horse briggs and stratton engine does the same thing. Was cutting deep grass and it quit. Tried to restart just makes a popping sound. When taken a compression check one cyl is 120 the other 90. When I check the compression on the one cyl it blows a rag out the intake, that I had to cover it. I looked at the keyway on the flywheel on the 22 hp and it appears to not have moved. I thought possible timing is off. Nothing underside of mower to stop it from turning. Any ideas