I have a Lawn Boy F series mower that is giving me fits lately. It ran fairly good until a couple of weeks ago and it started running too fast, like it was running lean so I cleaned the carb and put a new float kit in it, still ran the same, dying frequently also, so I put new crank seals in it and it still does the same thing. I've cleaned out the tank and fuel line, even blew through it with compressed air. It starts good when you prime it, runs for a few seconds and dies, you can keep it running if you keep priming it but when you stop priming it dies. I've tried two other carburetors and it still does the same thing.