I'm at my wit's end. Plugs are black. Engine sputters. Idle adjust has little effect except to keep it from dying. If I pull a vacuum line, engine revs up and responds to idle screw, so I believe timing is good. Spark looks good. I checked the coolant lines going to the choke and both sides were hot. Still need to pull them and check for obstruction. Both solenoids 'click' but the vent solenoid does not pull vacuum in either position if I pull the line off and connect/disconnect the solenoid. May pull the plunger and block the line just to see if it helps, but removing the air filter cover, filter, or even the whole intake up to the carb does not change anything. Fast idle cam never seems to move. Hot or cold. Choke butterfly is free. Still need to get a mirror to check position of it. If I rev it up, black actuator on choke moves up, as it should.