I recently just got a brush mower with a 8hp Briggs industrial plus horrizontal shaft . Some one had tried to get it running before I got it and I'm not sure what they had messed with . I cleaned the tank, replaced the petcock, new fuel lines , air filter , new fuel pump . Cleaned the carb by taking it apart and dunking it then spraying with carb cleaner and compressed air . I found the previous person didn't remove the jets because they came out hard . So I got it running but it hunts and surges . Almost dieing and small backfire at times . I checked for intake leaks with carb cleaner but nothing seems to stand out but it's also running bad enough that I'm not sure you could tell .I'm kinda running out of ideas . Thanks for any input