Hey All, new here and looking for help. I have a two yr old MTD with a 13.5 B&S on it. Would only run on choke so I pulled the carb and cleaned it. Put it back on and it will not start. New gas, new lines, bypassed the fuel filter and new spark plug. Nothing, rolls over fine, good spark when grounded to the head. Float bowl is full when removed. It has a solenoid fuel shutoff that is working at key on. I can prime the carb throat with gas and it'll fire up for seconds, if I place my hand over the carb's air inlet it tries to go. Got tired of fooling with it and bought new carb, not rebuilt, new. Same problem. Carb to head gasket is good and unit has good vacuum while cranking with airway blocked. Mower has two cutting seasons total so I don't think it can be worn valves. I've been doing wrench work for a good while now on push/riding mowers, an XVZ 1300 touring bike, a 250cc four wheeler, my vehicles as well as most of my families cars and trucks. This stupid mower is getting on my nerves. Any ideas? Thanks. Andy