ACE Hardware stores usually have a full selection, Home Depot and Lowes are hit or miss. Take your venturi with you, it is OK to stretch an o-ring a little to get it to fit, the stock OS ones are a small dia. cross section anyway. Smaller is better than slightly too big, that may leave a gap somewhere and result in an air leak.
Which, as it turns out, doesn't make a huge amount of difference. I saw a guy run half a season with both no o-ring to seal the venturi to the case, and. the fuel leaking into the engine around the right angle fitting, along the external threads on the spraybar, into the case, and in between the case and venturi. This was only a problem when it got hot enough that he bottomed out the needle and it was still too rich! It ran pretty much OK otherwise, and fixing it only improved the needle response.
For a "through the center" spraybar the only really critical leak area is around the threads of the needle. It's not recommended to let it leak elsewhere, but it's not necessarily a show-stopper, either.
Of course, with a sprinkler venturi any leak, even a tiny one, anywhere, makes a huge difference and *everything* has to be sealed up tight for consistent results. Including where the spraybar goes through the case - even the air leaking through the bead-blasting make a distinct difference. Silicone bathtub caulk is your friend and you will see it all around the front of any of my sprinkler venturi engines.
Brett
Topic: "O" rings (Read 2260 times)