What makes a petcock so special?

[Sam 78 GS750]

I've heard lots of people on here say that you can't rebuild a petcock...it will leak, that you have to buy new. I'm just wondering why that would be. It's a couple of moving metal parts and a couple of seals that fluid flows through, just like a lot of things on a bike.

No one would say the same things about carbs, etc. You just clean, replace the gaskets and o-rings and you're golden. Why would a rebuilt petcock be doomed to fail?

I'm not doubting or trying to start an argument. I'm sure the people that say that are speaking from experience, and I'll defer to that experience. I'm just trying to understand the reason why.

My petcock never leaked on me, but it has been on a shelf with no fuel in it for quite some time. I also have no idea if the internal seals, etc. have ever been replaced. Why couldn't I just replace those seals for a little insurance and call it a day?

[jsandidge]

I replaced the diaphragm and sealing o-ring on mine and it still leaked. I investigated further and found the spring to be weak. Stretching it didn't help, still leaking. Finally replaced the spring with a stiffer one from the hardware store, and it worked fine all season.

[gsrick]

I've had luck with some and others leaked. Most petcocks(not '78 1000) are in the $50 range and rebuild kits are $25. It just simpler to get a known good new one than take the chance or a failure and have to send back the kit , after complaining that is, and wait for another kit to arrive. THEN, pray the replacement works, if it doesn't, around you go. You'll see the small increase in price between the two, is worth it once you've been burnt by a leaking kit.

[Steve]

I have often wondered the same thing. I would attribute it to the lack of care and cleaning the petcock body. Yes, we soak and clean the carbs before replacing the o-rings and gaskets, but seldom hear of anyone doing the same for their petcock.

I have thought about collecting a few petcocks that have "failed" to see exactly what has failed and whether it can be rebuilt/repaired.

It is also quite possible that there are differences in the rebuild kits. Without knowing what brands are available, let's just say that "Brand A" has a kit with some really good parts. "Brand B" might have a kit with a slightly lesser-quality o-ring, and "Brand C" simply has a weak spring. If only we could determine which brand is "Brand A", we might have a success rate that is better than the typical 10-15%.

.

[chuck hahn]

The oring that comes with the rebuild kits is too fat on the cross section and they wont seat. Thats my deduction after wasting my money on one and then grabbing the calipers.

[hugo151]

The oring that comes with the rebuild kits is too fat on the cross section and they wont seat. Thats my deduction after wasting my money on one and then grabbing the calipers.

My rebuild kit worked but found the little o ring on the prime screw which wasn't included in the kit had failed

[chuck hahn]

Yours must be an 80 or newer bike. I was referring to the 79 and older lever styled petcocks.

[roeme]

From my experience with the one failed '79 petcock; unless you're able to manufacture all the rubber parts in the petcock by yourself, by using a kit you are taking a chance of wasting time and money versus a complete new petcock.

In my opinion that's because there are only few manufacturers that are willing to procure those kits to begin with, since these petcocks do contain kinda non-standard rubber parts, apart from the lip seal. Add to this that this is rather a niche market, so maybe there's not a lot of experience, not a lot of care going into these kits, or cutting corners...dunno. And often, they simply don't include all parts.

I do have saved this one petcock, and plan on rebuilding it by myself just for the heck of it and see if I can do it. If I can: the manufacturers probably suck. If I can't: either I suck (probable) or there's something everyone is missing when rebuilding those petcocks.

[Boriqua]

"What makes a petcock so special"

Nothing .. which is why I dont use one. I just need a valve that lets gas in and permits me to turn it off when not in use. I Pingel!

A bone simple heavy duty plumbing fixture.

[steve murdoch]

"What makes a petcock so special"

Nothing .. which is why I dont use one. I just need a valve that lets gas in and permits me to turn it off when not in use. I Pingel!

A bone simple heavy duty plumbing fixture.

Pingel petcocks are not infallible.
The o-rings inside can get pinched and a tiny rubber shard can end up downstream in the carbs.

[Sam 78 GS750]

Hmmm... what about using OEM instead of a rebuild kit? The o-rings and seals look to add up to about $15 vs $93 for the whole shebang.

https://www.partsoutlaw.com/oemparts/a/suz/50d3ff87f8700230d8b4df95/fuel-cock

Doesn't look like you can order the spring separately though... What else do you get in a rebuild kit that you can't just order from Suzuki?

That would remove the "quality of the parts" out of the equation. Seems like lack of thorough cleaning may have something to do with it. If you treat it like a carb rebuild and dip everything in Berrymans and scrub, think that may affect the outcome?

[bwringer]

Original petcocks die because over the decades, the original rubber parts shrink, harden and crack, springs relax, and quite often the metal body corrodes.

The parts in the aftermarket rebuild kits are ill-fitting low-quality junk. Yes, they work once in a while. Usually they don't. The odds are poor and it's not worth the gamble.

For some models you can get some of the OEM rubber bits, but not all. So that's not very useful either.


Yeah, it's frustrating -- you'd think modern civilization could come up with a decent fuel valve or at least be able to make the bits of rubber needed.

Look at it this way: the petcock controls the flow of a highly flammable fluid on top of a blazing-hot engine a few inches from your crotch. Is this really where you want to cut corners?

Buy a new petcock, skip a few frappawhappamochachinos next week, and ride happy for the next 25 years.

[Downs]

I think it's just Suzuki's vacuum fuel valves. I've had multiple Suzukis with vacuum fuel valves and none of them have worked. When I started bringing the GS1000 back to life we tried to get the fuel valve to work for us and I finally gave up and just spent the money on a Pingel and never looked back. It's not a perfect valve (nothing mass produced is) but IMO it's far better than the factory valves and is simple. On/Off/Res. What more do you need? What good is my fancy vacuum operated fuel valve if it leaks anyway.

[BCS Guy]

I had a problem with mine when I first picked up the bike. The prior owner had put a ball valve after the petcock because he didn't "trust" it. I split it open and found that he had the reassembled the internal diaphragm out of rotation, so it wouldn't flow unless on prime.

[bwringer]

Suzuki's vacuum petcocks work fine. They just don't last forever -- you usually get 20-25 years, which is pretty darn good in my book.

I've never understood why so many people want to write off the whole concept because the petcock needs to be replaced every few decades. But the topic comes up again and again and again around here -- there's a weird obsession for finding some magical petcock hack that will make it work forever.

Pingel valves don't last forever either, and with manual valves you're also depending entirely on the squishy wet glop in your cranium to remember to turn it off and on each time you ride -- the needle valves in the carbs are not designed or capable of holding back a tank of gas (and that doesn't mean they're defective; that's how they're designed), so you risk oil in the gas and even hydrolocking your engine if you forget just once. To me, that is simply not an acceptable risk.

Like I said earlier, replace the petcock if it's not working right, and think about something more useful and fun for the next 20 years or so.

I have to agree that it would be awfully nice if the rebuild kits were worth a damn.