Gas shutoff valve leaking

Guys, I need a little assistance.

Last year I took the "pot" off the bottom of my gas shutoff valve to clean it out and make sure it wasn't full of gunk. When I did this I found out the O-ring in there was destroyed.

I tried to make a rubber washer work, but it still leaks when the valve is switched on.

What size O-ring can I use to seal this thing up? I'm looking to sell my bike, and a fuel leak doesn't look very good for that.

you can get rebuild kits the o rings are odd sized and you would have to get real lucky to find one that fit go down to your local bike shop and tell them that you need a petcock rebuild kit and they shouldn't have aproblem at all finding one to fit.

Aha, I found a petcock O-ring kit on ebay. Sweet.