I have a 3.5hp Briggs &Stratton that gives a hard start and will only idle for a minute before stalling. I had it work for a while but stalled once I tried to cut the grass. I removed the carburetor cleaned it with carb spray , but same results. Removed the plug put in a new one and after three more attempts, it was fouled up(black). Cleaned it up, removed the air filter re-started but still only ran for a minute at an idle speed before stalling. Any ideas to solve this problem. Could it be the head gasket needs changing?

