Holy grail, "only" $137 but it is actually available

[pullshocks]

Ordered from Partzilla, it shipped immediately

[pullshocks]

When I got back from my "Making up for a lost season" ride http://ridersofvision.net/rovforum/index.php?topic=14958.0 and shut off the engine, gas started pouring out of the overflow tubes.  I pulled the gas lines from the petcock and found that  both the supply and return taps were failing to seal.  After draining the tank I pulled apart the petcock and found that fuel had leaked into the vacuum chamber, keeping the valves from springing closed.

There is no visible hole in the diaphragm, but evidently there is a leak.

I was not able to reach Lucky about his rebuild services.  I decided to bite the bullet and order up the new part.  Based on QBS's experience I am not 100% confident in the new part, and I will install shutoffs in both supply and return lines as he suggests.

I really believe these petcocks would perform a lot better with stronger springs, and that there is plenty of vacuum for the petcock to function with stronger springs.  This is something I am going to investigate.

A question for those who have rebuilt their '82 petcocks with the available kit--is the diaphragm made of flat sheet material or does it have contours molded in?

[The Prophet of Doom]

This doesn't answer your question sorry, but if you had fuel pouring out your overflows, you also need to look at your float bowl valves.

[pullshocks]

P.O.D.  thanks for bringing that into the thread.  It was on my list to check the float, needle, seat, and O-ring, but I did not mention.  All was well a couple months ago when I adjusted the float levels, but something changed during this ride (8 hours, 320 miles), petcock and needle,  both were non functional when I got home.  It could be one was already failing when I left and the other gave out during the ride.
I wonder if the tank of no-ethanol-added high octane fuel, or the dose of techron fuel injection cleaner pushed things over the edge?

[tig5]

I'm curious, what is the benefit of the stock petcock? I understand it has some kind of prime function but does it actually help with performance or operation? My bike came with a simple replacement petcock and I've since replaced that one with another simple one when it started to leak. My bike certainly hasn't been problem free but I haven't had any issues that I'd relate back to the petcock. Why is this the "holy grail" and why do I need one?

[QBS]

"Holy Grail" in that it is '83 specific, '83 tanks will accept no other petcock, rebuild kits are not available and, until this post came up, thought to be extinct.

The thing that drives all this is the '83 exclusive fuel gauge.  Otherwise, an '82 tank could be installed on an '83, the '83 fuel return line blocked off, and victory declared.

[The Prophet of Doom]

I'm curious, what is the benefit of the stock petcock? I understand it has some kind of prime function but does it actually help with performance or operation?

I'd say it would be a safety thing a) in an accident if fuel lines get ripped off, and b) if the float valve fails to seal completely then you will dump all the fuel in your tank out the overflows - or if blocked into your engine.

It won't affect Tig, but the 83 petcock also has fuel return to the tank if I remember correctly to keep the fuel cooler.


Here's a good writeup of a petcock rebuild with pictures
http://www.xs650.com/forum/showthread.php?t=20662

[couchflyer]

Doom, nice link, very informative.

[simcha]

Read this post last night and thought I remember one of these in my spares box. Had a look today and indeed I do have one. Seems in reasonable external condition, not damaged in anyway and does not seem to have been taken apart. Is it any use to anyone? I have an 82 model and am in England so I doubt I will ever use it. It is missing the plastic filter and pipe that fits inside the tank. If you would like it let me know? Would maybe swap for other XZ / Vision parts for mt (long running) rebuild.

[johnclemens]

I would suggest a pingel petcock.
It can be had for much cheaper than stock and it's waaaay better.
They make an adapter plate that fits the vision. Can't remember which one it is. You just measure between screw holes.

It eliminates the crappy vacuum valve. Starts better too.
You do have to remember to turn off the fuel though..

Www.pingelonline.com

[The Prophet of Doom]

I've been wondering about fitting an electric low pressure fuel pump. They are about the same price as a mikuni rebuild kit.
Would that would eliminate the need to turn off at a manual petcock as well?

[guzzi john]

 Says $128.21 today. Yes '83 only but fits A/C Vision too! Same petcock & fuel pump. GJ ::)

[fret not]

A check of the Pingle website shows they also have a vacuum operated petcock in casde you want to retain that feature.

[pullshocks]

Good to see Mr Clemens drop by. 

I did look at the Pingels,  it looks like good stuff. 
Since this is an 83 with both supply and return lines it would need 2 petcocks. I decided coming up with adapter plates was more than i wanted to deal with.  Especially  if trying to retain the plastic tubes that extend up into the tank