Maybee this should be posted under "What have you done to your XS today?" But anyhow, the vacuum petcock on my 81 special too was pristine when I got the bike eight years ago and stayed that way for about six years . I started seeing the sighns of leaks in the form of gasoline varnish around the sealing surfaces and while I never saw it drip ,it eventually stained the left carburetor and engine case. It's been on my list for a while ,so today, as I was already covered in gas from another project I decided to get it done. I dumped the tank and pulled the tap off. It was covered in varnish. I completely disassembled the tap carefully removing the gasket/O- rings with the aim of reusing them. Thouroughly cleaned all mating surfaces. The four-hole gasket was in good shape but flip-flopped it anyhow. There were no sharp edges on the back of the lever. And the diaphragm was intact. For reassembly I put a light film of plumbers grease on the old O-rings. I know that the manual says to use nothing here but the fuel tap is basically a plumbing fixture. Interested to know what people think of this practice. Cleaned up the under side of the tank were varnish had hardened under the gasket and touched up a few tough spots on the tap with carb cleaner. Anyhow , no visible leaks yet. Time will tell. As others have already pointed out, rebuild kits are not always required. I have been through my carburetors 4 or five times,reusing gaskets and other parts. ORings are cheap at the local hardware. That's my two cents. Happy trails.