Why does a Briggs and stratton 12.5 HP lawn mower engine stop 2-3 seconds after it starts?

Answer 1

This problem is almost always a carburetor problem. You can try to spray some carb cleaner into the carb then let it dry and try it this will probly take several times. If this doesn work the best way is to take off the carb and clean it really good by taking some it apart where you can spray carb cleaner and then use some compressed air to really clean the deposits or dirt or whatever the blockage is. This is the way I do it. Some times it takes using a really thin gauge of mechanics wire to clean out the passages and such. Hope this helps. Additionally a series of engines sold on lawn equipment had galvanized steel carburetor bowls which would begin to rust out if any water entered the fuel system. Removing the bowl is a simple operation but please look up instructions in the owner's manual. This rusting produces a fine slurry of zinc and iron oxides which will clog the jets and intakes in the carburetor.