I have a 12 hp briggs and its shooting flames out of muffler and inside of muffler turns cherry red. Sounds like engine is running under a load. Has about 95 pounds of compression and takes a bit to get it to start. Was thinking might be a partially sheared flywheel key, burnt valve, or blown head gasket,HELP!!!!!
Fly wheel key and Briggs go hand in hand, also check the valve, but more so, check to make sure the tolerance between the valve and the lifter is not too tight. That will cause flames and red mufflers as well. If it is not a valve, flywheel key, or tolerance, it sounds like you are running too lean on the mixture, but not with compression as low as you read it. I am back to valves and clearance again...Try that....
