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Thread: Fuel Leak

  1. #1
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    Default Fuel Leak

    My 1980 GS750L started leaking fuel. I walked out into garage and there was a puddle of fuel on the floor. It appeared to be leaking from the ignition cover. Without doing an extensive inspection I believe the fuel is leaking from the carb bowls. I had notice a small leak from them last month after a very short ride around the block. The bike is new to me and I was told the carburetors had been rebuilt. I'm thinking the petcock is not doing its job and allowing fuel down into the carbs, it overflows, finds it's way down to the ignition cover and drips out the weep hole in the bottom. Bike is on it's center stand. I placed a pan underneath to catch drips. I welcome any thoughts on this.


    1980 GS750L

  2. #2
    Nessism's Avatar
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    For one thing, make sure your petcock shuts off the flow of fuel when the engine is turned off. And don't leave your petcock on the prime position.

    Secondly, needless to say you need to pinpoint the source of leakage. The most common reason is because of a blocked or worn out float valve in one or more of the carbs. There is a carb rebuild tutorial linked in my signature which may help you.

    Lastly, never trust anything the previous owner says about the maintenance status of your bike. Learn for yourself.

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    Redman's Avatar
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    You didnt leave the petcock in PRIme position did you?
    If so, that is your problem.

    THe carb float needles cant be expected to complelty shut off gas flow, so the auto petcock provides that function (but cant if you leave in PRIme position).
    Pull/pry the big line off the petcock, see if the petcock is shutting completly off.

    Other concern: Might now be gas in your crankcase oil.

    >>Later note:
    Oh, an L.
    Some of those petcocks dont have a lever. . . . . not sure which do or dont.
    Last edited by Redman; 12-08-2021 at 03:06 PM.

    Had 850G for 14 years. Now have GK since 2005.
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    If your petcock looks like one in this eBay link, be suspicious Ö.and understand how itís supposed to work
    https://www.ebay.com/itm/New-Petcock...-127632-2357-0
    1981 gs650L

    "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

  5. #5
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    Yes, an "L" with no lever. vertical slot=Prime, horizontal =Run. yes? if so... then I was in prime. I set it to run using a very narrow flathead screwdriver. The bike is in for the winter and I plan on replacing all fluids before riding next year.


    1980 GS750L

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    rphillips is offline Forum Sage Past Site Supporter
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    Still can't imagine anybody would ever design such a (don't want to say STUPID but can't think of a better word) pet cock. Mine had the PRI kind'f at a diagonal location, neither vertical nor horizontal, just had to guess at it. Thankfully it only lasted a yr. or so.
    1983 GS1100E, 1983 CB1100F, 1991 GSX1100G, 1996 Kaw. ZL600 Eliminator, 1999 Bandit 1200S, 2005 Bandit 1200S, 2000 Kaw. ZRX 1100

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    Quote Originally Posted by tom203 View Post
    If your petcock looks like one in this eBay link, be suspicious Ö.and understand how itís supposed to work
    https://www.ebay.com/itm/New-Petcock...-127632-2357-0

    Yup, That's it.


    1980 GS750L

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    Nessism's Avatar
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    Quote Originally Posted by Pete Wrigley View Post
    Yup, That's it.
    The service manual describes how that petcock functions.

    With the slot in the prime position a pulse of vacuum from the engine pulls the internal diaphragm open, and a check valve holds it open until the slot is turned back to the run position.
    Last edited by Nessism; 12-09-2021 at 08:43 AM.

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    This forum is so great. I appreciate all the help guys. From the little I've read so far the reason for this type of petcock has something to do with the bike having a fuel gauge. I'm not sure of all the technical detail behind it. Can I just leave it in the "run" position?


    1980 GS750L

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    Burque73's Avatar
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    Quote Originally Posted by Nessism View Post
    The service manual describes how that petcock functions.

    With the slot in the prime position a pulse of vacuum from the engine pulls the internal diaphragm open, and a check valve holds it open until the slot is turned back to the run position.

    That's interesting. I would have figured it to operate the same as others. Turn to PRIme and fuel flows. I'd be the one to try and prime the bowls while putting my gear on and then hit the start button. This makes me even more thankful for the later model G design.




    Quote Originally Posted by Pete Wrigley View Post
    This forum is so great. I appreciate all the help guys. From the little I've read so far the reason for this type of petcock has something to do with the bike having a fuel gauge. I'm not sure of all the technical detail behind it. Can I just leave it in the "run" position?
    Quote Originally Posted by Redman View Post
    You didnt leave the petcock in PRIme position did you?
    If so, that is your problem.

    THe carb float needles cant be expected to complelty shut off gas flow, so the auto petcock provides that function (but cant if you leave in PRIme position).
    Pull/pry the big line off the petcock, see if the petcock is shutting completly off.

    Other concern: Might now be gas in your crankcase oil.

    >>Later note:
    Oh, an L.
    Some of those petcocks dont have a lever. . . . . not sure which do or dont.
    Roger

    Current rides
    1983 GS 850G
    2003 FJR 1300A
    Gone but not forgotten 1985 Rebel 250, 1991 XT225, 2004 KLR650, 1981 GS850G, 1982 GS1100GL, 2002 DL1000, 2005 KLR650, 2003 KLX400

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