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Discussion Starter · #1 ·
Is it possible for the petcock to leak internally? My tank never hits reserve. When i last filled up I added 2.7 gals to an 81 custom tank. I normally fill up around 120 miles. It's not really an issue. If I ever did need reaerve it would be nice to know it's there.
 

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It might be missing the "straw". The gas flows through the straw when the petcock is turned to "on". when the gas level is below the straw it starves out. Then you turn the lever to "reserve" and it draws the fuel from the bottom of the tank, ignoring the straw. If the straw is gone, so is reserve.



You could unbolt it from the bottom of the tank, take it out and check. (siphon out the gas first). Maybe you can see it with a flashlight from the filler hole, not sure.
 

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Discussion Starter · #3 ·
My straw is installed in the petcock. I do have a gas leak when I switch from main to reserve. If the seal is bad inside the petcock I'm thinking it could leak internallny no matter where i have the valve set at???
 

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The straw is a good guess. The second that makes people feel dumb is not turning it the right way and going straight to reserve instead of on.



There have been a few noted occasions where vacuum petcocks fail to hit reserve from the on position and keep supplying gas. It has happened to WisconsinCx.
 

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I is possible that it is in the petcock assembly itself. There is a rubber disk with 4 holes under the selector knob. The selector has a groove on the back side that when turned, covers one hole or none. One hole is reserve, one is regular. If this rubber disk is cracked between those two holes, fuel could indeed flow from the reserve to the regular side. It would probably leak too, which you say yours does.
 

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Sometimes you can remove the rubber disk and turn it over. That presents an new surface and has worked for me in the past. I even made a disk out of hard rubber once. That didn't work quite as well as I had hoped for,if I remember correctly.
 

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'84 CX650E that is evolving into a GL500
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I have tried a couple of experiments for replacing the rubber disc in my vacuum petcock:



1) GL1000/1100 petcock disc from Randakk's Cycle Shakk. (Randall does not recommend this.) This disc is smaller than the correct one but has the holes in the right places. It leaked a drop or 2 when switching to reserve when first installed but stopped in a couple of weeks. When removed after a year of use it had grown to the correct size and after drying out for a couple of months it did not shrink and was still pliable. All of the fuel you can buy here has 10% ethanol - I don't know whether this had any effect on it.



2) Suzuki part #44341-28070 (I bought 2 - the second one can be yours for $8.50). The diameter & thickness are correct but the holes are not quite big enough. I modified mine with a file. Like the Randakk part, it leaked a drop or 2 when switching to reserve when first installed but stopped in a couple of weeks. When it has been in for a year I will take it out and examine it.



BTW:If you look for a petcock on eBay, make sure you ask the seller whether he is measuring the threads or the flats on the nut. A petcock that has 18mm on the flats will have 14mm threads.
 

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My first CX ... Way back when .... had this problem. A rebuild kit solved it's problem.

I found out by running out of gas that day. about a mile from the gas station.

long walk with a gas tank in hand.
 

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Those petcocks on Ebay cost a FORTUNE! My Nos one was about $50. I am installing it on the tank as soon as it is out of the paint shop.
 

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I recommended this to Need for Steed and he likes his.
I think you will find that the 18mm that seller means is the measurement across the flats on the nut (in other words you need an 18mm wrench), not the diameter of the threads.
 

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I think you will find that the 18mm that seller means is the measurement across the flats on the nut (in other words you need an 18mm wrench), not the diameter of the threads.


I wonder if that's the case, if so, it should fit the 14mm threads on the non-vacuum models. Maybe i'll ask the seller a question...
 

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I think you will find that the 18mm that seller means is the measurement across the flats on the nut (in other words you need an 18mm wrench), not the diameter of the threads.




At the bottom it says this.



FITS TANKS WITH 18 MM MALE THREADS .
 

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I recommended this to Need for Steed and he likes his.



http://cgi.ebay.com/ebaymotors/HONDA-ATC-TRX-FUEL-VALVE-PETCOCK-18-MM-_W0QQcmdZViewItemQQitemZ380180879594QQptZMotorsQ5fATVQ5fPartsQ5fAccessories



I just purchased and installed this one at Blindstitch's rec. and you will need a small hose clamp fot the line out of the p-cock and clamp off or otherwise seal up the other hosed you don't need for the vac and air . I am very happy with it once I made these small discoveries. !8.00 not bad price .
 

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The only thing about this new petcock is the reserve is very small , I got 13 miles after switching to reserve .
 

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Discussion Starter · #19 ·
I'm going to pull my petcock tonight to verify that lever is correct when I turn it to main and reserve. Maybe I can also see if it is leaking internally. If not I'll be buying a new one off E-Bay
 

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I'm going to pull my petcock tonight to verify that lever is correct when I turn it to main and reserve.
ON should be straight down, and RESERVE should be straight up.



R
 
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