How to rebuild your leaky or starving petcock

Okay, after much googling,
http://www.maxim-x.com/petcock.html
http://www.xs11.com/forum/showthread.php?t=36960

http://www.maxim-x.com/images/sm3-plungerseals-stockseal-close-marked.jpg Pic with common damage from Maxim-x website.

I have came up with an solution. One of the sites eluded that the original Taiyo Giken petcock has changed its piston o-ring material. Apparently it was more pliant, softer, more mold-able. Where as the new ones are solid rubber.

So with me eluding to a solution, I have bought some viton 0-rings "4 MM X 1 MM BN70"
http://amzn.com/B000RBZ8C2
I bought them for carb job. it was a 5 ring pack, I only needed 2.


I was using K&L2699 kit

So what is the solution? with BN70 o-rings? On the piston, I was able to remove the original oring, put one of those o-rings (4MM) Then I put the original oring over the top of that one.

Of coarse I was able to use a dremel, bought a bullet shape polishing cushion, and some polishing agent. I shined up the piston mating surface, and used a nut to push the spring to push for more pressure on to the piston (too big) then I downgraded to a cut-up electrical female connector. Regardless after testing vigorously, inhaling fuel vapors, I found it had worked. I am guessing it was the double o-ring solution that worked.
Sorry no pics
 
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After a year of re-building this bike, I decided to try to fire it up. I didnt even bother taking the battery off the trickle charger as the petcock leaked. I anticipated this and had my shop rags ready. In any event it seems to have a good seal to the tank I think the leak is coming out of the valve.

My 2 main culprits would likley be the waver washer and the o-ring on the valve. The O-ring is a no brainer to fix and a replacement should be quick cheap and easy (my 3 favourite words). I just want to clairify the waiver washer position.

I had the waiver washer installed before the turn valve with o-ring .... am I to understand that the wave washer goes on after the turn valve with o-ring is inserted then the petcock cover plate goes ontop of the wave washer? Or did I have it right the first time with the wave washer installed then the valve with o-ring then the cover plate? :shrug:
 
http://xjbikes.com/Forums/viewtopic/...c/start=0.html

A pic cans say a thousands words. That thread shows this pic.

am I to understand that the wave washer goes on after the turn valve with o-ring is inserted then the petcock cover plate goes ontop of the wave washer?

So as I understand, yes, per the pic, wavy washer goes on after the turn valve.
Tobie

ps that is what is neat, when I was solving the leaky petcock, I did a search on the name found on the petcock. Taiyo Giken, and found that web site. So our issues are not just ours alone, and as such, Use google to help us! and I try to pass on back to us!
 

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I had to have a laugh about myself over this one. For all the time a rescearch put in I figured the petcock was pretty standard. So ON and RES are self explanitory in my narrow mind, I did have a vast misunderstanding of the PRI position... and prettymuch the whole thing.

I never knew that you can leave the petcock in the ON or RES positions when the bike is off and fuel flow will automatically stop. PRI or PRIME for some reason in my mind was where the petcock gets set when the bike is off and not running.

Glad to know I dont have any leaks and the actual floats are working just fine... cause fuel was coming out of the left air filter.... :yikes:

In a perfect world I would have kept this to myself as if it never happened :laugh:
 
The typical rebuild kit, seems to forget to work. Which is why I tried throwing a o-ring at it. Proof positive that it works is to just pull hose off the petcock. If it leaks oops. Anything position but prime.
 
Okay, there is no such kit anymore. but Amazon reported this model is what you need. (Double Check)
http://bit.ly/189HMDI
K&L Supply Fuel Petcock Repair Kit 18-2698
The above link will google that next line automatically. My hope is that google will show you source venders near your neighborhood.

Also note that the name on the outside of the petcock will help draw on other sources for info. Just like one of my earlier post, clicked on maxim, and another one, was very helpful links.
 
My fuel doesnt seem to stop even when the bike is not running. Gas is coming out of my air filters as well. Any words of wisdom.
 
My fuel doesnt seem to stop even when the bike is not running. Gas is coming out of my air filters as well. Any words of wisdom.

There might be a small tear in the diaphragm, and maybe a weak back-spring. Gas could be pushing on the vacuum valve causing it to run to the carbs, and leaking through the diaphragm into the vacuum line going to the intake boots.

I had the same problem earlier this summer. Here's what I did to turn it into a simple on/off petcock:
http://www.xs400.com/forum/showpost.php?p=138570&postcount=4

You might also want to check your carb float valves and see if they're sealing properly, but my money is on the petcock first.
 
Are you doiing the same thing as Post 25 said? (TimmyT) leaving it on the "Pri" mode? verses just leaving it on the "On" or "Res" mode?

The gasket kit is out there still, check local sources first, then once you get it, you can fix it. Like the last poster said, I thought i had poor backspring action, I put a nut in there. I dont' think I needed to do that, once I started the doubled up on my washers. my trick is still working, since I did it. I am sure my tip is in this thread.
 
My fuel doesnt seem to stop even when the bike is not running. Gas is coming out of my air filters as well. Any words of wisdom.

If your petcock is leaking through, even when it should be off, rebuild it as per the instructions in this thread or find a compatible replacement. Unless it's being left in PRI mode.

As for the gas coming out of the carbs, which model bike/carbs do you have?
Is this happening when your bike is on, off, or both?
Have you narrowed down whether is coming through the carbs from the petcock as jaredK suggested or from the carbs themselves?

The petcock is already leaky so that could be it, but I'd check the carbs too.
If it is them you most likely have too much gas flowing into your carb float bowls. Could be a couple of things.
The floats could be set too high, not closing the float valve before the gas overflows.
The floats could be set correctly, but something might be stopping them from closing the float valve. Could be debris inside the valve, could be something loose, bent float axle. No way to know without looking.
 
My fuel doesnt seem to stop even when the bike is not running. Gas is coming out of my air filters as well. Any words of wisdom.

The other thing about gas coming out your air filters, that gas had to by the H tube, which is connected to your breather, which means you problably have gas in your oil,:doh: which means its time to change your oil.:banghead:

(since we know nothing about you, Nice intro, I put my bike info, and reminders in the Signature line, click on control panel, and edit signature. Put you specific bike 3 digit code in there, and we can assume a better assumptions.

IMPORTANT NOTE our petcock wasn't just built for our bikes, so look at my post, starting with ... After much googling, ... Those links have excellent pics, and more tips. I have been in contact with one of those webmasters, with my suggestion. of doubling up the O-Ring's, to give a better contact for sealing. post 22
 
Hi Yvette,

Sort of like surgery, in order to keep it clean, you want to post your question in it's own thread, and we can answer it there. Posts are sort of like one way streets, they tend to lead only to one ending, and you have to start your own street to lead to your answer.

We'll be with you every step of the way.

Regards,
Drewcifer
 
I'm new to this forum and bikes in general and came across this thread while trying to rebuild my petcock.

I ordered the rebuild kit for my '79 xs400 and I'm a little confused since a few of the parts look slightly different from the ones I have. How am I supposed to take off my old plastic spacer and put it on to my new vacuum vale (like it looks in the pictures of this thread)? I can't seem to find a way to take the valve apart to sandwich the spacer inside.
 
Hard to say without seeing your petcock to know whether it has different requirements.
One user bought the rebuild kit before realizing a previous owner had installed a similar but different petcock which required a different kit.
Even with the right kit though it is tricky to get the old diaphragm out of the plastic spacer and the new one in.
The plastic spacer and diaphragm should come out together. Just yank the old diaphragm out, taking note of how it was positioned and which way it was facing
The new one can be pushed in partway, enough to pull the two rubber membranes of the diaphragm to either side of the spacer.
It's finicky.
 
Post some pics of what you have. All you have to do is pull half the rubber diaphragm through the spacer. Then line it up with the backing plate. There was a guy a while back that seemed to have a different style of diaphragm than what these bike came with stock. He replace the entire petcock with one that was rebuild-able.
 

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