Restrictive petcock

[ccratin]

I can't imagine why it would not be rebuildable. I assume your test showed it was not holding vacuum? The rebuilt kit contains a new diaphragm and o-rings and should restore it to like new.

Chris

[prism4]

what should i use to clean it with for the rebuild?

[Hoomgar]

I'm an advocate of the stock vacuum petcocks. I know for myself that a pingle would spell certain death for my bike if left in my control. The stock petcocks however work flawlessly if properly maintained. Any bike that gets close to or over two decades old should have all fuel delivery components rebuilt anyway so blaming the design is a mute point since it most likely worked fine for the last 15 years and finally needing a rebuild is therefore not a crime. Rebuild kits can be had anywhere almost like local dealers or eBay sellers. I use Georgefix on eBay a lot. Just email him. A rebuild kit can be had for a fraction of the cost of a pingle and a 1/10 of the installation time compared to converting to a pingle.

Just my two cents but I encourage rebuilding and keeping the stock petcock.

Once all the rubber bits are removed simply clean it out good with carb cleaner and a soft brissel brush if needed. I have used vacuum petcocks on all my bikes over the last 23 years and have only had to rebuild 2 in that time. Both on separate bikes. Easy, normal maintenence.

Hope that helps.

[ccratin]

Check that diaphragm closely. Is the rubber cracking/brittle looking? Is it separated from the little piston? If there is nothing broken on the casting, there's no reason it won't rebuild.

[prism4]

Okay I went and got a rebuild kit put it all together and still have the drips?? I applied vaccum to the line and it does not hold. slowly escapes. What should it hold at?

[Hoomgar]

Okay I went and got a rebuild kit put it all together and still have the drips?? I applied vaccum to the line and it does not hold. slowly escapes. What should it hold at?

Then you either damaged the new diaphragm, don't have it installed correctly or something else weird? If you replaced all the rubber parts in the valve with new then you should be done.

Check your work. You say you apply vacuum and it doesn't hold? How are you doing this? Are you maybe applying too much and damaging it?

[jeff.saunders]

I've noticed a couople of things in repairing petcocks.

1) Some are beyond repair - the wear and tear on the petcocks results in worn metal parts as well as hard/cracked rubber parts. Corrosion of the metal, exposure to fine rust particles (grinding paste) ruin the seats / sealing areas in the petcocks. I reckon only 50%-70% stand a chance of being repaired when they are that old. The diaphragm versions seem to repair better than some of the manual petcocks.

2) Multiple petcock variants. I know with some of the Kawasaki petcocks the design changed slightly during the course of the production run. I have seen plenty of examples of petcocks where parts just will not fit correctly in one version, but fit perfectly in the other. Yet when you look-up the part numbers, only one part number for the petcock exists.

3) Rebuild kit O rings - on some diaphragms, the little O ring that seals works better if it's replaced with a slightly larger O ring. I'm not sure if the O ring is really the wrong size, or the spring behind the diaphragm is too weak - regardless, the result is gas gets by the daiphragm seal.

[RichardW]

If he is still getting drips of gas out of the vacuum line it has got to be the diaphram or the mating surface of the cover/body. Or like Hoomgar said, maybe applying too much vacuum.
Somebody correct me if I'm wrong, but could you use a tiny bit of sealant on both sides od the edges of the diaphram? Maybe the housing is pitted?

[ccratin]

I'd be much less worried about a slight drip from it if it is in the ON or RES position. Where I'd be concerned at this point is whether or not it pulls gas through the vacuum line. If you installed everything properly and didn't damage the new diaphragm, it should be ok. Because the vacuum chamber on it is so small, a tiny leak even in your test hose would leak the vacuum very quickly. If the vacuum causes fuel to flow and doesn't allow fuel to come into the vacuum line, you are probably pretty good.

As for stopping the leak, pull it back apart and clean the sealing surfaces really well and inspect to make sure you don't have really deep pitting or abnormalities in the surface. To clarify, where are you seeing the fuel drip coming from? Out the fuel line or around the lever? Did you pull apart the lever and change the o-ring on the shaft?

[mixongw]

Hopefully I won't have to fool with another petcock. I got my solenoid valves installed. When the ignition is turned on, the solenoid opens for the main tube. I have a switch on my handlebars to turn on the reserve. It's wired through the switch to the ignition voltage and turns on the reserve tube. I used my old petcock and did some sawing and grinding (and some JB Weld) to come up with a two tube (main and reserve) port that bolts into the old petcock location on the tank. It works like a charm!

[prism4]

Ok I got it fixed. Thank God! but I like the idea of using solenoids to engage or disengeg the fuel. Can you post some instructions and pics so that we could do that as well . I appreciate everyones help.

[mixongw]

Ok I got it fixed. Thank God! but I like the idea of using solenoids to engage or disengeg the fuel. Can you post some instructions and pics so that we could do that as well . I appreciate everyones help.

I'll see what I can do.

[petelister]

'79 GS750L fuel shutoff valve

I'm following this discussion thread with interest. My petcock was vandalized, broken clean off. I can't find a replacement, stock or otherwise, locally. Any leads on where I might score one? Thanks for any help you can offer.

[ccratin]

eBay. They are on there all the time. Many fit multiple models, so check the parts fiche to see which ones you can use.

[Hoomgar]

Hopefully I won't have to fool with another petcock. I got my solenoid valves installed. When the ignition is turned on, the solenoid opens for the main tube. I have a switch on my handlebars to turn on the reserve. It's wired through the switch to the ignition voltage and turns on the reserve tube. I used my old petcock and did some sawing and grinding (and some JB Weld) to come up with a two tube (main and reserve) port that bolts into the old petcock location on the tank. It works like a charm!

Clever, I like it