I've had it with this mower. It is a old 90's craftsman riding lawn mower I got off a friend for free. The mower was sitting in his lawn for years so I asked and I received. I thought I would be a fun project but has turned into a nightmare. It has a 15hp Briggs ohv engine. When I first got it it didn't run but I put a new magnito and spark plug on it and it runs... But not very well. It will surge to high and low rpms. When too much throttle is applied or mower deck is activated it will start sputtering requiring me to disingage the mower deck and throttle down until it decides it wants to run again. I have cleaned carb very well, replaced oil, checked valves ... The whole nine yards but it still throws a fit and won't run... Someone please point me in the right direction