100 people are going to tell you to switch to a pingle... I guess 100 people can't be wrong...

If you stick with OEM, here's two important things:
1. the main flap (labeled "3" in this picture) is different on each side, make sure you assemble it right.
This picture seems clear enough that you should be able to tell which side goes how:
http://www.valkyrieforum.com/forum/tech_archive.cgi?read=13776792. There's a test you can do, after you rebuild the petcock, and before you even screw it back
onto the tank, that will almost
assure that you have got it put back together right:
http://www.valkyrieriders.com/shoptalk/petcock.htmNow that it is all back together. Its time to test it to ensure it works properly and won’t require pulling the tank back off later. Simply attach a (Clean) rubber hose onto the vacuum nipple. Apply a slight vacuum to the hose while looking down the fuel outlet. Yes, your mouth works great for this! Just don’t suck very hard. It’s very easy to overcome the spring tension. As you apply vacuum/suction you’ll see the diaphragm pull away from the main section. When you release vacuum/suction the diaphragm will SLOWLY return sealing off the flow of fuel. If it does not either you assembled incorrectly or your check valve is still clogged or defective. If all works, you’re done!Good luck!
-Mike