Fixed leaking petcock; Don't buy a new one yet!
 

*Mods, I'm not sure whether to put this in the How-To or Troubleshooting section. Move where appropriate if needed!*

Hi guys! Being a graduate student I have not been able to contribute as much as I'd like to, but I had finally been presented with the first issue my bike ever had: a leaking fuel petcock. This is a common issue on the GZ, and can present itself many different ways:

1. Leaking underneath the tank at mating surface gasket to petcock.
2. Leaking out the petcock fuel selector switch.
3. Not stopping flow without vacuum and overflowing carburetor due to malfunctioning or misadjusted needle seat.

I was firstly presented with the number two scenario. I searched on here and saw that some people saw that when dirt had worked its way into the switch and caused some minor leaking. When I disassembled my petcock, I did not see any dirt, but it stopped the leak, so I didn't think any more of it.

Well, the time came to adjust my valves, so I removed the tank, and was met with a nice, nearly unrestricted flow of gasoline out of the petcock, even though the engine was not running and it was not set to prime. Luckily, my needle seat was still working so I didn't have a puddle of gasoline waiting for me in the morning. So I figured maybe some dirt had gotten between the o-ring on the vacuum actuated valve and it wasn't closing all the way. Well, when I disassembled the petcock for a second time, I saw how bad a shape the o-ring was really in. It was no longer round, and looked to be mashed at a weird angle on the edge.

http://s15.postimage.org/lad0v2nsn/PICT2650.jpg

So I tried many things, like turning the o-ring around, stretching it, letting it sit overnight to reform its shape, and it still leaked no matter what I tried. This o-ring is a tapered o-ring, and if it gets damaged or mis-shapen, it will leak no matter what you do. Gz rider has a post on this issue already. (Shoutout from Kannapolis Gz rider! :retard: ) He has much better pictures of disassembly. I strongly recommend you to read this before attempting any repairs! Here is the link:

http://www.gz250bike.com/forum/viewt...hp?f=10&t=5281

The o-ring in question is the one pointed to in red. His was actually better off than mine...

Thing is, at least here in K-Nap, is you can't find any tapered o-rings. But when I started thinking about it, I figured it really wouldn't matter whether it was tapered or not as long as you got the right thickness to allow compression, but also for the vacuum of the engine to pull it off when running. So I set to work finding the perfect size o-ring for replacement, as it is much cheaper than $80 for an entirely new petcock all because of a small doughnut of rubber. (More difficult than it sounds, trust me!)

First off, be sure to look at picture four in Gz rider's post. This shows the o-ring location, and the opened up petcock. Be very careful with the diaphragm and internal gaskets. You can't replace those, and they are very fragile! One nick, and it will either leak, or not be able to hold vacuum to actuate the valve and all this will be for nought!

http://s7.postimage.org/gsh2bhbnb/image.jpg

Secondly, you need NITRILE (Buna-N) or VITON o-rings. These are the only materials that will stand up to the gasoline exposure. If you just get regular old unlabeled cheapies, they will disintegrate, and you will be cleaning a black, sticky goo out of your petcock, carb, and possibly your gas tank. Nitriles are cheapest and work just as well as the expensive VITON's, so if you can find them, then use them.

Ok, here we go. The EXACT size you need is as follows: ID=4.8mm OD=8.6mm Thickness=1.9mm
I needed some other o-rings, so I bought a kit for $10 at Harbor Freight. If you have a Harbor freight near you, these are the exact part numbers: Kit item#=67580 Exact o-ring part#=P5 or 008 in the kit. Here's a pic:

http://s11.postimage.org/d3nndekrz/PICT2656.jpg

Ok, so easy enough, just pull off the old o-ring and replace it with the exact one mentioned above, or if you have the kit, o-ring 008. When you put the petcock back together, you'll notice the two halves of the valve do not sit flush all the way down like before unless you push them together. THIS IS WHAT WE WANT! This was the way it should have been new from the factory, it means that the o-ring is thicker than the worn out original and is making contact with the mating surface without engine vacuum applied, sealing off gas flow.

There are considerations here! NOTE: NOT ALL O-RINGS ARE THE EXACT SAME SIZE! EVEN IN THE SAME BATCH! If it is too thick, the vacuum will not be able to pull it back enough to allow enough fuel to flow. If it is too wide, it won't seal correctly and will still leak. If it's too narrow, it won't seal against the mating surface and will still leak. Test it first! Here's how.

1. Get a hand-held vacuum pump. If you don't have one, no worries (I don't!), but make sure all the gas is out of the petcock, because you'll be putting your mouth on it...
2. Locate the brass fitting on the petcock that goes to the vacuum line on the carb, marked in red in the picture. Suck on it to give it vacuum. You should hear something move inside the valve while you are doing this. This tells you everything inside is still moving and still working, and the diaphragms are ok.

http://s15.postimage.org/rwfc16mfb/image.jpg

3. After putting it under vacuum, hold that vacuum inside by plugging the fitting with your tongue. Now take your other finger and start tapping on the main fuel outlet that leads to the carburetor bowl on the petcock. This is the fitting you took the fuel line off of (still attached in picture). This will give you a distinctive hollow sound, as access to the yellow tubes that go inside the fuel tank have been opened with vacuum.
4. Now pull off your tongue while still tapping on the main fuel line outlet; you should hear the sound change to a less hollow tone. That means that the o-ring has returned to a resting position in the valve and sealed off flow to the gas tank pick-ups.
5. One last test! Since it is supposedly sealed, attempt to suck on the main fuel line fitting on the petcock (where the fuel line was attached). If you can't get any air to come through, no gas is going to be able to leak through!
6. Mount in tank, turn tank rightside up, and see if any leaks out the petcock. If not, turn the valve to the prime position to see if any starts to flow. If so, turn to reserve position to ensure it stops flowing and is not leaking there either. If not, SUCCESS! Mount on bike and go for a ride. When you shut off the bike, squeeze the fuel line going from the petcock to the carb. You should not hear any bubbling inside the tank after the first squeeze or two, which is symptomatic of gas bubbles being forced up into the tank from the petcock, meaning it isn't sealing.

Here is a pic of the old and new side by side (apologies for my sucky camera!):

http://s16.postimage.org/cu1v2zgu9/PICT2654.jpg

This worked for me on the first try, and I have not had any issues. So make sure you get the EXACT size o-ring listed. Also, if yours still leaks and you don't want to spend $80 on a new one, you can get one from a Suzuki LT80 or KFX80 for around $18. It is not vacuum operated, but it has the same mounts and gasket shape and tubes with reserve, so you just mechanically shut off the fuel when parking the bike and plug the vacuum line to the carb. Many people actually prefer this, as they usually don't leak (ever!). Here is an ebay link to those valves should this not work for you if you want to save some money:

http://www.ebay.com/itm/190618010208...9#ht_963wt_952

Hope this helps someone else with this issue/saves them $80!

Regards fellow riders,
-GZlocal

*Update* So a quick update. I've had the o-ring in the petcock for about 2 weeks, and I have had no issues at all. The bike doesn't leak, and doesn't starve for fuel under full throttle, so the o-ring is sealing and unsealing completely normal. I also disassembled the petcock to check the o-ring's shape, and it seems to have a tapering to it now, although not quite as much as the original o-ring had. Which leads me to believe that the o-ring may never have been tapered from the factory, and may very well just do that with age to a point where it will no longer seal correctly.

Re: Fixed leaking petcock; Don't buy a new one yet!
 

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Re: Fixed leaking petcock; Don't buy a new one yet!
 

Ok, I'll edit for the pics, thanks! Yea, I was actually wondering the same thing. I'm going to pull the petcock again to check for any abnormalities after letting it sit for about a week, and then I'll check the shape of the o-ring. I would imagine it would conform to the shape of the seat eventually, as nitrile likes to reshape itself. I'll post back any findings in that regard, and hopefully my bike will still be in my (working) possession in a year for a full report, if these crazy Kannapolis/Charlotte drivers don't smash it up for me.

On a side note, I'm a student at UNC Charlotte, and someone had the audacity to steal my oil plug! That was nice to find at 8:00 at night after a 14 hour day...hopefully they won't steal the entire bike!

Re: Fixed leaking petcock; Don't buy a new one yet!
 

Excellant info. Good info on the O-ring material.

Re: Fixed leaking petcock; Don't buy a new one yet!
 

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Re: Fixed leaking petcock; Don't buy a new one yet!
 

No, no angry ex's. They stole the oil plug. Not the filler plug on top, but the actual plug on the bottom. I had a puddle of oil under my bike and no oil plug to contain it. I had to call my buddy to give me a ride to ridenow powersports in concord before they closed at 9 so I could buy a plug and 2 quarts of oil. I just changed it two days before with Shell Rotella T6 synthetic. Whole ordeal cost me about $40. Needless to say, I became extremely intoxicated that night. :bong:

Re: Fixed leaking petcock; Don't buy a new one yet!
 

Are you sure you remember tightening the plug properly? It's easy to put it in finger tight, then get sidetracked, & forget to go back & tighten it up before filling the oil. Could've taken a couple of days to shake itself loose. Seems more likely than someone bringing the correct wrench & then crawling under a bike in a public place, then having to get cleaned up because they got oil all over their hands. :??:

Re: Fixed leaking petcock; Don't buy a new one yet!
 

Yep.A friend of mine done the exact same thing,except his oil plug came out when he was riding causing him to crash.Consider yourself lucky.
O_o :cry:

Re: Fixed leaking petcock; Don't buy a new one yet!
 

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Re: Fixed leaking petcock; Don't buy a new one yet!
 

No worries Gz rider. And oh yes, I absolutely torque it down tight. I learned that lesson a long time ago when changing the oil on my car. I have a torque wrench, but I usually just use a breaker bar and get it very snug to avoid things like this, because it would be difficult to remove with a standard socket wrench that way, which most people carry around in their cars. I don't believe it was necessarily an act of theft as much as it was an act of vandalism. I guess someone hatin' on bikers maybe.

I know they stole it because there was no trail of oil leading up to my parking spot. And there would have been since the speed limit is a ridiculous 20 mph. There was also no plug under my bike if it had to have happened to fall out there. I'm telling you, the things I've seen around that campus are beyond something any normal human would do.

Re: Fixed leaking petcock; Don't buy a new one yet!
 

So a quick update. I've had the o-ring in the petcock for about 2 weeks, and I have had no issues at all. The bike doesn't leak, and doesn't starve for fuel under full throttle, so the o-ring is sealing and unsealing completely normal. I also disassembled the petcock to check the o-ring's shape, and it seems to have a tapering to it now, although not quite as much as the original o-ring had. Which leads me to believe that the o-ring may never have been tapered from the factory, and may very well just do that with age to a point where it will no longer seal correctly.

Re: Fixed leaking petcock; Don't buy a new one yet!
 

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Re: Fixed leaking petcock; Don't buy a new one yet!
 

Yea, tell me about it. I would rather have my hindquarters whipped than go through that again. I wish it was my own stupidity (which I'm VERY guilty of VERY commonly). Now I'm paranoid to drive it there on a daily basis. Way to screw up my entire plans for buying the bike in the first place.

New plug only cost me $4. So to whomever stole it, I would like to publicly announce that I do not condone behaviors straddling that borderline upon pure evil incarnate and insanity. So as a personal message to my unseen vandal, :fu: :fu: :fu: :fu:, from all four of my appendages. :)

Re: Fixed leaking petcock; Don't buy a new one yet!
 

Sorry, but I'm still not convinced about the vandal theory. Like GzRider said, you've got to know exactly which plug it is, then contort yourself into an uncomfortable position under the bike, then undo a badly designed plug with the correct wrench. I've often convinced myself that there's nothing I've forgotten (like torquing it up tight) then having doubts, some time later, & finding out that those doubts were well founded. It's just one of us fallible human being things. :)

I reckon a vandal is more likely to do something easy, like one did to mine. Chop the starter motor cable, which is quick, easy, and unobtrusive to do.

Re: Fixed leaking petcock; Don't buy a new one yet!
 

Nice friends you have Alan. :cuss: :mad:

Re: Fixed leaking petcock; Don't buy a new one yet!
 

Well, all I know is all you need is a 17mm socket and a 3 inch extension to get to it. I think those are pretty common tools in any cheapo socket wrench set and are pretty commonly carried in vehicles. I know I have a set in my car, and if I was looking to raid someone's ride or cause mischief, that would probably be the first thing I'd have in my trunk, so I don't think it's all that far fetched.

Besides, what is more evil? Cutting your starter wire so you immediately know something is wrong with your bike and can't go anywhere, or draining your engine oil hoping you don't notice the puddle and then driving away only to have your engine seize while riding, destroying your bike as well as the skin on your lower body when you lay the bike down? Parking is terrible at UNCC, and seeing a small motorcycle taking up an entire parking spot is enough to set someone off. I know that for a fact, I've seen it happen. Girl actually let the air out of this guy's car tires because he beat her to a spot. Crazy.

But, for the benefit of ALL doubts, it had to have "fallen" out in the parking spot as I said before. There was NO oil trail, not even a drop. It's not like it would have fallen from the Empire State building, so it would be in the immediate vicinity of the bike. It was not. I looked everywhere in, around, and near my spot. So, if that so happened to be the case of the plug spontaneously falling out, someone still picked it up and made off with it. Unless it did happen to fall out while riding and my bike magically doesn't sling out oil when running with no plug. If that was the case it magically would have fried the perp when he got close to my bike.

Moral of the story is, I now have a hex bit oil plug, which is not a commonly carried tool of destruction. So whether you believe it or not, the whole ordeal sucked, and from my assessment of the situation when I was there pointed entirely to an outside act of intervention. I will always admit when I am wrong (or more commonly stupid), but since it was my first oil change on the bike, I double checked everything. I only changed it two days before, and I clearly remembered double and triple checking everything, even down to the oil filter orientation. In this case, I was the victim of an unseen cretin. Plain and simple.

Re: Fixed leaking petcock; Don't buy a new one yet!
 

Yes, such considerate "friends" to chop your starter cable. I haven't looked, but can those be fashioned out of like normal small battery cables or is it semi-proprietary?

Re: Fixed leaking petcock; Don't buy a new one yet!
 

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Re: Fixed leaking petcock; Don't buy a new one yet!
 

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Re: Fixed leaking petcock; Don't buy a new one yet!
 

I KNEW that guy that sold me the plug at Ridenow looked suspicious! I bet he's the one who boinked my plug! :yes: lol

Because of winter not many people are riding, but some I've spoken to have had things randomly happen to them in a similar fashion. Caps go missing, cables get cut, tires get poked. I think/hope it was an isolated incident. Random things like that happen all over campus. Most people I know that ride bikes have Ninjas or Sportsters, and they have alarm systems. But good fortune does not have a habit of following me around.

I found a plug from a Mercedes I think that was the same thread size. It is a 14mm Allen head bolt. I matched them up with the one I bought at Ridenow. My buddy worked for a trucking company, and these types of bolts are common on diesel trucks. So he swapped me one. I know you can get them online pretty cheap, and I know some motorcycles use those to begin with. I'm not sure what the sizes of the threads are, I can look them up and post them if people wish. That way you can cross reference them with plugs online if anyone wishes to make a swap.

And I hope the tire company wasn't the one I buy my tires from...I seem to pick up a lot of nails...

Re: Fixed leaking petcock; Don't buy a new one yet!
 

It was chopped so close to the lug that I was able to crimp another lug on, then slightly reroute the cable to give me an extra couple of inches to rebolt it. I reckon I know who did it. The day before, I had to go down to one of the other apartments to complain about the noise. There are 18 apartments in the block. We all own our own, except for 5 which are rented. For some reason the owner always seems to rent to scum. This one was rented to a guy who works in a mechanic's, so I reckon he'd have the heavy bolt cutter that's needed to give the cut pattern that was on the cable. I reported it to the police & told them what I suspected. Not enough to get him arrested, but at least he knew that the police were involved.

Re: Fixed leaking petcock; Don't buy a new one yet!
 

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Re: Fixed leaking petcock; Don't buy a new one yet!
 

"Oh sir, I so terribly sorry to hear that. Well, you're in luck, we do have a replacement oil plug in stock for you for $3.96, but may I ask why you're going through all that trouble to replace your oil plug when we have a brand new Virago 250 here?" O_o

Re: Fixed leaking petcock; Don't buy a new one yet!
 

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Re: Fixed leaking petcock; Don't buy a new one yet!
 

Ha! To them, 1000cc is a sissy bike. They like to push the 1400's on people for the profit margins, although they sell a crap ton of 250's there. They just don't make much off of them.

Re: Fixed leaking petcock; Don't buy a new one yet!
 

So, another update. It's been two months and the petcock is still leak free!

On another sad note, I will be selling my GZ250 this week to upgrade to a...........DUM DUM DUM!!!!!!...........Honda. :itsokay: Got a brand new CBR250r for three grand. I had to do it!

I'll still be around the forum whenever I can be. School has me pretty tied up, but I know the bike like the back of my hand, so I'll be glad to help where I can!

Re: Fixed leaking petcock; Don't buy a new one yet!
 

Well, I'm sure if it leaks when this guy tries the valve adjustment next time, I'll be getting a phone call. I made it clear for us to stay in touch so I could help him if he ran into any issues. What was most important to me was this bike would be taken care of. So, like I said, I will constantly be around this forum, so if I hear it started leaking again, I will let the forum know! Even if a new o-ring only lasts a year, getting a pack of that size from lowes for $3.49 is enough to last for 5 years. And from what I saw come out of that thing, I'm sure those silicone o-rings are much higher quality than what came in the petcock from the factory.... :rawk:

Good to see you again 'rider! :2tup:

Re: Fixed leaking petcock; Don't buy a new one yet!
 

Hello again all! Sad to see GZ Rider has departed since my last visit, but things happen...

Anyway, three months and no leaks. So at the request of the late GZ Rider, this seems to be a perfectly successful repair. I recommend trying this before buying a new (expensive) petcock!

I do have the patcock described in original post as manual alternative (linked on eBay). It wouldn't fit GZ without some modifications. The knob in reserve position will interfere with the tank weld seam. There might be similar petcock with distance from knob to mounting flange larger that is more suitable for GZ as non vacuum operated replacement.


I purchased this one. Not sure if the screws are same distance but gave it shot. Will let you know if it works. It looks like valve it further from mounting flange:
http://www.ebay.com/itm/321479366875...%3AMEBIDX%3AIT