$40 petcock on Amazon/eBay?

I need to buy a new vacuum petcock since my rebuild didn't completely stop the petcock from leaking on the ON setting. The kit did indeed make a huge difference since it previously didn't stop any fuel from pouring out, but it's still seeping out. That said, has anyone bought or had experience with these $35-40 petcocks on Amazon or eBay? Here's the link: www.amazon.com/dp/B01N9HA4M3/ref=cm_sw_r_cp_apa_QCVWzb05PTWF9

I could use the opinions of the B&B here.

I have not used one of those, but one crucial step that many folks skip during a rebuild is carefully polishing the seat where the tiny oring is supposed to seal against, and the face of the lever that is supposed to seal against the smiley-faced oring. A tiny rough spot caused by a tiny bit of corrosion or hard debris can cause seepage. A little time, a micro fiber towel and some high quality aluminum polish can make a noticeable difference.
If the face of the lever is noticeably pitted or rough, you may need to start with some 800 or 1000 grit sandpaper taped to a piece of glass. Keep the area of the paper that you will be rubbing the valve face on wet with Wd40. This will keep the paper from getting clogged, and will reduce the chance of stuff being sanded off from getting embedded in the face of the lever.

What rebuild kit did you try? The oem diaphragm assy & tap gasket are still available from the dealer.
When I rebuilt mine, I did as TexasKZ mentioned & polished the mating surfaces with brass wool.

As for that aftermarket petcock, it's listed as 34mm. What's the bolt hole spacing on your fuel tank?
An oem 51023-1375 petcock might be 44mm. It has a larger/wider fuel screen than the 34mm petcock & i know for sure it uses a larger petcock body o-ring where it contacts the tank. so this leads me to surmise that the spacing would be 44mm.

edit: at Z1Enterprises.com the oem 51023-1375 petcock is listed as 44mm.

Ive fitted 2 rebuild kits in mine and its still pissing fuel out.I also followed this tutorial;
www.xs650.com/threads/rebuilding-yamaha-...lves-petcocks.20662/
which I found very informative. (Not so much now as the photos have disappeared). Ill be doing it again soon,as Im off the road til its sorted. Very frustrating.
Someone suggested (as a cowboy fix) to fit a basic on/off tap further down the fuel line. It wont work for me as there is no space to get my fingers in to operate it.