We could give you more direction if we knew what engine you have that you are having issues with. Please provide model number of engine so we can see what you are working on.
Briggs and Stratton 15.5 narrows it down to about 250 variations. The reason I asked for the model number was to determine if this is L head, OHV, Opposed twin, V twin, because they all have different approaches to repair. I L head, or Opposed twin the model number will be on the blower housing either over the spark plug, or could be a a tag next to the flywheel The OHv engines will be stamped into a valve cover.