I am doing some maintenance on a ~25 year old garden tiller with what I believe to be a 5.0 HP Briggs & Stratton motor. I have no manuals for this thing. Cars I have worked on have had spark plug gaps from .026" to .090". Out of the box, the replacement spark plugs for this motor have had gaps from about .030" to .050". What gap should I be using for the spark plug?
If you get the serial number off the engine the Briggs and Stratton website has the info you need, including where to find the serial number on older motors. After 25 years the odds are pretty good that the plug isn't even the correct one for your motor. I seem to remember it being .030 for some and .040 for others. Perhaps the difference was a Tecumseh/Briggs thing. Researching the serial number is the way to go though.