I have a john deere rider with a 17 HP briggs. It was blowing blue smoke and pushing oil out of breather tube. Oil had fuel in it so I rebuilt carb(thinking it was bad needle or seat) and drained and refilled oil. Tried running it but same problem. Next I replaced the head gasket. Test ran and after about 5 minutes running the thing backfired and shut down. I restarted and let it run again for about 5 minutes. Shut it down and restarted. Now it is back firing on restart when engine is hot. Also after a about 5 minutes running it chokes down and almost dies(same issue still). I pulled breather tube off of carb, started it and when running at full throttle again i am getting gas blowing from breather tube again. So again it has gas in the sump but I turned fuel off the night before and checked the fuel shutoff and it is working. Its still getting gas in the sump but not while sitting. The gas is going into the sump while its running. My theory is that something is wrong with the fuel pump and its allowing fuel to flow backwards from pump down the vacuum line that is attached to the engine. Any thoughts or suggestions would be helpful. I can not think of any other way that much fuel would be entering sump when the engine is running.
