My John Deere D170 stopped running after running rough for a while. I replaced the fuel pick up (it was obstructed) and cleaned the fuel tank. I replaced the fuel filter, fuel pump, and carburetor. I replaced the air filter. I replaced the spark plugs and checked for spark. I adjusted the choke linkage. It won’t start with full choke. If I remove the air filter and put my hand over the air intake, it will start. It runs well with full power for a while but then stops running. I would appreciate any advice.