Hi Guys,
Have just removed primer bulb to replace as it wasn't pumping fuel to prime engine and found a tiny rubber ring and a micro spring with a ball bearing in it. Asuume its a form of non return valve ???
Where does it go and which way around should the rubber ring go??
Photos would be appreciated or a parts diagram as I can not find anything online.

Part #105:
 
https://www.partselect.com/PS8981344-Briggs-and-Stratton-494409-Seat-Check-Valve.htm 
 
The smooth part side of the seal should be towards the check ball...
 
I don't know off hand exactly where it goes so back track where you were.
There can't be too many spots for it to go...
 
.