I'm an experienced auto tech and am unhappy to say im getting my butt kicked by a mower. Used for plowing, thus it sat all summer. Wouldn't start when it came in. I changed the fuel and fuel filter and had a look as the plug, whick looks new. It started one time after that and sounded ok, but would not re-start later. The engine cranks fine but floods the cylinder before there is ever any sound of ignition. Has spark. Pulled and cleaned the carb bowl and verified the solenoid pulls in when powered. Blew out the jets. No change. If I leave the choke on, it fires out the exhaust. The muffler is imploded as if it lit off when full of fuel sometime in the past. Pulled the cover on the OHV and verified that the valves are moving. I worked on a lot of old Briggs motors but don't know where to go with this thing. HELP!