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12 volt fuel shut off valves? Because.. that gawd awful vacuum petcock

S

scratch

Forum Mentor
Super Site Supporter
after a couple of years of playing with jet's to perfectly match the Kerker, my gal's 550 is a screaming meany... revs from 1K to 10K instantly and you have to hang on... it's awesome... never run better.

But...

That gawd awful vacuum petcock.

It's failing, again... and I'm done with it. Unfortunately as the bike in question is a 1980 L, there's no room for a Pingle, and an in-line shut-off would be impossible to reach, as the stock unit feeds toward the center of the bike.

Anyone ever add an in-line 12 volt fuel shut off valve?

Does anyone have any reason why I shouldn't attempt it?

While electrics aren't my area of expertise... Seems to me that I could leave the old valve on prime, wire an electric valve to the bikes lighting power circuit and be done. (or an on off switch on a relay). Am I missing something?
 
scratch said:
after a couple of years of playing with jet's to perfectly match the Kerker, my gal's 550 is a screaming meany... revs from 1K to 10K instantly and you have to hang on... it's awesome... never run better.

But...

That gawd awful vacuum petcock.

It's failing, again... and I'm done with it. Unfortunately as the bike in question is a 1980 L, there's no room for a Pingle, and an in-line shut-off would be impossible to reach, as the stock unit feeds toward the center of the bike.

Anyone ever add an in-line 12 volt fuel shut off valve?

Does anyone have any reason why I shouldn't attempt it?

While electrics aren't my area of expertise... Seems to me that I could leave the old valve on prime, wire an electric valve to the bikes lighting power circuit and be done. (or an on off switch on a relay). Am I missing something?
Click to expand...
Interesting idea, but I've never seen one. Now if you ad more hose, you can route an inline fuel cutoff over to the side of the bike where it can be reached. I've done this on a few bikes, but they eventually wear out. Have you bought a new petcock and it failed or did you attempt a rebuild and it failed?
This is the one I've used, $5-8 at most parts and hardware stores in the lawn mower section, but as I said they only last a few years. I've had it were I can tuck it out of sight and it makes a good anti theft device. They may still steal it, but unless they find it they won't get far.
7044f4b9-8d8f-4343-ac40-4d4ef9203e66_1000.jpg
 
gsrick said:
Interesting idea, but I've never seen one. Now if you ad more hose, you can route an inline fuel cutoff over to the side of the bike where it can be reached. I've done this on a few bikes, but they eventually wear out. Have you bought a new petcock and it failed or did you attempt a rebuild and it failed?
This is the one I've used, $5-8 at most parts and hardware stores in the lawn mower section, but as I said they only last a few years. I've had it were I can tuck it out of sight and it makes a good anti theft device. They may still steal it, but unless they find it they won't get far.
7044f4b9-8d8f-4343-ac40-4d4ef9203e66_1000.jpg
Click to expand...


It's had a rebuild but lasted only 22 months... another rebuild is probably the way to go... and moving a shut-off to the other side is also a great option (why didn't I think of that! )

Mainly this idea cam out of disgust with this vac-cock, we both have 80 550's and it seems to be a re-occurring problem. Her bike is running so fantastic now that all the jets and mixtures and sycs are dialed in... and it has to get docked because I'm concerned fuel will leach down the vacuum line and get in the motor. Grrrr...

I've seen so much amazing stuff on this forum over the years that guessed someone here may have gone to an electric unit and could offer a pointer or two.

(In the meanwhile I'm gonna route a shut-off to the other side while I wait for a rebuild kit)

thanks again
 
... you would want a solenoid type valve, I guess...like irrigation uses...not a motor driven type....so valve is only open when power present.

I wouldn't bother with such a set-up myself. If your "Prime" works, just turn it to non-functioning vacuum position to shut off.(..or get one like Above ^^^) You could tie a string from your leg to the tap to remember to shut gas off before dismounting. You'd soon get the new "habit".

oh and ...plug the vacuum outlet on carbs of course..
 
Why doesn't my 30-year old petcock fail, but his does?

Sh!tty gasoline?
 
In the interests of "keeping it simple", my other bike is an XS650. Yamaha also fitted vacuum operated fuel taps which also suffer from the ravages of time. The solution is to buy new direct replacement off/on/res petrol taps from the XS suppliers. I haven't looked closely but such taps might fit suzuki tanks...?
 
When you rebuilt the petcock did you verify the function of the check valve built into the back cover? The function of the petcock is described on page 306 of the factory service manual and if the check valve failed, which is very common, the prime function will not operate. Your plan to add a shut off valve is fine and all, but unless the petcock is modified it won't flow any fuel without vacuum pulling the diaphragm open.

Easiest and best solution is to purchase a new factory Suzuki petcock.
 
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Rebuilds are unreliable. Get a new petcock and be good for another 30 years. The stock petcocks don't fail when new.
 
Gorminrider said:
... you would want a solenoid type valve, I guess...like irrigation uses...not a motor driven type....so valve is only open when power present.

I wouldn't bother with such a set-up myself. If your "Prime" works, just turn it to non-functioning vacuum position to shut off.(..or get one like Above ^^^) You could tie a string from your leg to the tap to remember to shut gas off before dismounting. You'd soon get the new "habit".

oh and ...plug the vacuum outlet on carbs of course..
Click to expand...

That's pretty much exactly what I had in mind, a soleniod valve... I was wondering if anyone had done it yet.

The prime "works" its just one of those nasty little inset plastic screw primes... not something you would want to use every day. We have other bikes with regular valves, remembering isn't the problem.


roeme said:
Why doesn't my 30-year old petcock fail, but his does?

Sh!tty gasoline?
Click to expand...

I had another 1980 that was in far worse shape, more miles and ratty as hell but it never failed. It was an E, this one is an 1980 L valve and they are different...


Jonathan said:
In the interests of "keeping it simple", my other bike is an XS650. Yamaha also fitted vacuum operated fuel taps which also suffer from the ravages of time. The solution is to buy new direct replacement off/on/res petrol taps from the XS suppliers. I haven't looked closely but such taps might fit suzuki tanks...?
Click to expand...

would have done that years ago but as the original post says... theres very little clearance on the L and the factory L valve is actually horizontal not vertical to compensate for this... perhaps this is also the reason why they are more prone to failure

Nessism said:
When you rebuilt the petcock did you verify the function of the check valve built into the back cover? The function of the petcock is described on page 306 of the factory service manual and if the check valve failed, which is very common, the prime function will not operate. Your plan to add a shut off valve is fine and all, but unless the petcock is modified it won't flow any fuel without vacuum pulling the diaphragm open unless you mod the petcock.

Easiest and best solution is to purchase a new factory Suzuki petcock.
Click to expand...

Of course.. the bike has been a daily driver.. it functioned fine, it still "functions" yet it is starting to fail... applying vacuum to the hose now draws a trickle of gas down the vacuum hose...
And yes, if adding a solenoid I understand I would have to neuter the original valve, clearly the fuel would have to be able to reach the valve har...

Fixing or replacing it is of course the easy way and the meanwhile I have a rebuild kit on order, and while I wait I'm putting in an in-line routed to the other side.


Again really just wanted to know if anyone had tried this particular idea and I know there are some electrical wizards here who might have gone this way and could suggest mounting, grounding, wiring options as well as actual valves or perhaps a relay type on off?
 
JTGS850GL said:
Rebuilds are unreliable. Get a new petcock and be good for another 30 years. The stock petcocks don't fail when new.
Click to expand...

In general I agree... though I'm not convinced the 1980 L is a multi year petcock with it's poor functional ity out of the box and modern corrosive fuel... perhaps perhaps not... But, like stator wiring on a goldwing, or fuse box mods on an XJ... sometimes there's another option besides stock. Sometimes mods are fun.
 
scratch said:
In general I agree... though I'm not convinced the 1980 L is a multi year petcock with it's poor functional ity out of the box and modern corrosive fuel... perhaps perhaps not... But, like stator wiring on a goldwing, or fuse box mods on an XJ... sometimes there's another option besides stock. Sometimes mods are fun.
Click to expand...

Trust me... If a new stock petcock was failing at any rate we would be hearing about it. As for poor functionality... WTH are you talking about? They worked pretty good for years when new. Don't be confused with horror stories after 30 years of use compared to when new. As for liking to mod thinks up. Have at it. I like to do the same sometimes. Just don't complain if things don't go right. As for using some type of electronic valve, just make dam sure that it is fuel compatible.
 
imo the vac petcock is pretty frickin reliable, and i suspect (many, many)more engines have been flooded from manual shutoffs (and forgetting to shut them off) than from vacs. but mods are cool too. though I suspect an electrical valve would be less reliable in the long run than a vacuum one.
 
Vacuum petcocks are pretty dang reliable. The problems typically only show up after 20+ years and when people purchase junk aftermarket rebuild kits trying to fix them.

And again, there is a check valve built into the back cover of the leverless petcock and when that fails you got no prime.
 
...sooo nobody really knows what makes them fail, right? They just last around 2-3 decades? (because then mine would be due methinks...but I see no sign of them wearing out)
 
roeme said:
...sooo nobody really knows what makes them fail, right? They just last around 2-3 decades? (because then mine would be due methinks...but I see no sign of them wearing out)
Click to expand...
They fail because of old brittle rubber, just like the carb o-rings. And tires. And brake lines. Rebuilding them would work if the replacement parts were correct, but they aren't. The o-ring is too small, and the diaphragm doesn't seal, at least for long. Suzuki used to sell the rubber parts, those should be better if they are still available. You probably won't know it has failed until your crankcase fills up with gas, followed by a puddle of thin oil coming out your shifter seal.
 
JTGS850GL said:
Rebuilds are unreliable. Get a new petcock and be good for another 30 years. The stock petcocks don't fail when new.
Click to expand...

Nessism said:
Vacuum petcocks are pretty dang reliable. The problems typically only show up after 20+ years and when people purchase junk aftermarket rebuild kits trying to fix them.

And again, there is a check valve built into the back cover of the leverless petcock and when that fails you got no prime.
Click to expand...


Yep and yep.

Quite frankly, I'm astonished you got any use whatsoever from a rebuilt petcock. You're very lucky there.

Slap a new one on, and sometime around 2050 it will probably fail. Such a hunk of junk -- only lasting 30+ years of being submerged in crappy gas.

Oh, and guess what material is inside an electric valve doing the sealing? That's right, the same good old Buna-N rubber...


Anyway:
http://www.dan-marc.com/79-afc11112.html
 
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bobgroger said:
They fail because of old brittle rubber, just like the carb o-rings. And tires. And brake lines. Rebuilding them would work if the replacement parts were correct, but they aren't. The o-ring is too small, and the diaphragm doesn't seal, at least for long. Suzuki used to sell the rubber parts, those should be better if they are still available. You probably won't know it has failed until your crankcase fills up with gas, followed by a puddle of thin oil coming out your shifter seal.
Click to expand...

I rebuilt the petcock on my KZ with OEM Kawasaki parts and the petcock works perfectly. I wish Suzuki sold proper petcock rebuild parts because if they did we probably wouldn't be having this discussion.
 
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