Ive neglected this engine for over a year. Left about a gallon of fuel in it which when the float stuck on the carb leaked into the crankcase. I did not realize that i left fuel in it, so i fuel it up and it fired right up. It smoked alot ran for 5 seconds then died and would not restart. I figured it would be a gummed up carb so i pulled it off and cleaned it out. Still would not start. Out of habit I checked the oil which reeked of gas. I drained the oil from the engine and it was extremely thin almost like water. I then filled the engine with 20 w 50 oil figuring i would change the oil after i got it running to try to get all the fuel out. Long story short machine still will not start even with starter fluid. Ive pulled the plug and I have good spark. I then pulled the muffler of to see if there was any blockage. When i tried to start the machine without the muffler flames came out of exhaust port and the it backfired through the carb. It did these each time i tried to start it (over 10 times) I'm wondering if this engine has hydraulic lifters that are being affected by the thin oil that was in the machine or the thick oil that i just put in it. Any help with this would be great.