Bill, You may remember that the idle disc on the Perry carburetors had two small black "O" rings. I've used Ace Hardware Story O rings in that application. The only problem I've had with their O rings was in a gasoline application. I tried them in a Bing slide valve carburetor on my Mini Max ultralight, and they swelled up.They are cheap enough that you could get a couple, and soak them in glow fuel to see if there are issues.