One step forward and two steps back. Today I tried to start my B&S 5hp horizontal on my tiller and its now "coughing" back through the carburetor. Its not backfiring as its not hitting at all, it seems to be coughing compression out through the carb. I'm thinking I have a burned intake valve thats not seating all the way or leaking. After I rebuilt the carb it seemed to be running ok, as well as a tired 21 year old engine can. Does this seem plausible? Any other suggestions?