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Thread: 1980 gs550e - fuel tap / tank noise

  1. #1
    Join Date
    Jan 2015
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    Somerset, UK
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    Default 1980 gs550e - fuel tap / tank noise

    I have a bike as above and when ever it gets near to reserve a tapping sound is heard
    in the tank?

    It must be vacuum pulses from the petcock creating this sound amplified through an emptying tank ?
    (Even with the tank beside the bike with a long line the sound is still present so it is not
    engine / frame.

    The bike has a fuel line to petcock and a vacuum pipe to carb 3. Standard RES and On only (no prime)
    The internals are fine and it works perfectly.

    Does anyone else have this ?
    I wonder if it is doing damage when i let the petrol level get low.

    I attach a diagram of my petcock - the original.
    it has no prime and to fit on my bike due to access the fuel and vacuum pipe must point forward or to the right not backwards.
    (Anyone know where i can get a petcock with prime as above ?)

    Petcock my one diagram.jpg
    Last edited by ukjules; 06-18-2017 at 06:04 AM.
    UKJULES
    ---------------------------------
    Owner of following bikes:
    1980 GS550ET
    1977 RD 250
    1982 GPZ 750 R1
    1980 GSX 250E

  2. #2
    Join Date
    Apr 2008
    Location
    plymouth uk
    Posts
    7,880

    Default

    if you have a tank gauge then it could be the float hitting the inside of the tank when the level gets low
    Last edited by Agemax; 06-17-2017 at 05:28 PM.
    Viva La Figa

    1978 GS1085.

    "THE PROBLEM IS NOT THE PROBLEM,THE PROBLEM IS YOUR ATTITUDE ABOUT THE PROBLEM" ......Captain Jack Sparrow

  3. #3
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    Jan 2015
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    Somerset, UK
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    Default

    No tank guage , standard.
    It is the petcock and vacuum pumping ...
    I just wondered why only my bike does it ?
    Always has ... Always will.

    I am convinced all other 1980 GS
    With only Res / on on petcock must ?
    UKJULES
    ---------------------------------
    Owner of following bikes:
    1980 GS550ET
    1977 RD 250
    1982 GPZ 750 R1
    1980 GSX 250E

  4. #4
    Join Date
    Jun 2010
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    Kent
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    3,033

    Default

    Try putting the lever to prime position and blocking the vac pipe?


    Don't say can't, as anything is possible with time and effort, but, if you don't have time things get tougher and require more effort.

  5. #5
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    Jan 2015
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    Aha .... Yes no prime on this tap as per diagram
    it is the standatd one.

    It makes a rattling sound as it gets near to Res.
    Switch to Res disappears.
    Disappears when full too.

    I am just readying the bike for a " tour "
    and would so like a tap with prime but
    The feeds must point forward or inwards.

    I'll go as is as not an issue just a noise ?
    I can't see how others with same tap do t get it .
    UKJULES
    ---------------------------------
    Owner of following bikes:
    1980 GS550ET
    1977 RD 250
    1982 GPZ 750 R1
    1980 GSX 250E

  6. #6
    Join Date
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    Newport News, Virginia
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    I would love a petcock that did that. Most of the other '80 models got a petcock without a lever with a little nylon screw slot that was run (horizontal) or prime (vertical), no reserve. My tanks were in terrible shape so I got a '80 NOS tank for my '78. Does your petcock have a 50mm bolt spread? Mine looks like this (https://www.z1enterprises.com/petcoc...t-spacing.html), it is a KL number but is identical to the stock petcock.
    Last edited by OldVet66; 06-18-2017 at 07:28 PM.
    '78 GS1000E, Dyna-S ignition, Dyna Green Coils, K&N pods, Delkevic SS 4-1 exhaust, Dynojet Stage 3 jet kit, Russell SS Brake Lines, Progressive suspension, Compu-Fire series Regulator 55402 and Advmonster cree LED headlight conversion.

  7. #7
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    Jan 2015
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    Somerset, UK
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    For the 1980 gs550et - the petcock plate bolts from end to end is 50mm.

    On my original as per diagram (earlier in thread) there is no prime. Vacuum only which makes it hard to start
    after being left for a while. Also makes the sound in question when nearing reserve.

    I attach a petcock that i used on my last Europe trip borrowed when mine disintegrated.
    It is off a suzuki but i dont know what.
    50mm outside to outside so fitted fine but the pipes point the wrong way thus i had pipes
    coming out around the outside of the bike.
    It is however the type i need - has all the logical elements anyone using as bike needs when out
    on the open road. Why oh why are there not more of these types being made ?

    I need one like this but the pipes pointing forwards or near as.

    Non standard petcock but fits - pipes point wrong way 1.jpg
    UKJULES
    ---------------------------------
    Owner of following bikes:
    1980 GS550ET
    1977 RD 250
    1982 GPZ 750 R1
    1980 GSX 250E

  8. #8
    Join Date
    Jan 2015
    Location
    Somerset, UK
    Posts
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    Default

    And just for info - my standard one - with just on/off (no prime)
    but pipes pointing in the right way for use on my bike.

    Note - I think center to center is 44mm using m6 bolts
    to attach to tank.

    Petcock my one diagram 1.jpg
    Last edited by ukjules; 06-19-2017 at 07:40 AM.
    UKJULES
    ---------------------------------
    Owner of following bikes:
    1980 GS550ET
    1977 RD 250
    1982 GPZ 750 R1
    1980 GSX 250E

  9. #9
    Join Date
    Jul 2015
    Location
    Switzerland
    Posts
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    Default

    Quote Originally Posted by ukjules View Post
    (...) Why oh why are there not more of these types being made ?

    I need one like this but the pipes pointing forwards or near as.

    Non standard petcock but fits - pipes point wrong way 1.jpg
    '79 550 petcock might be what you're looking for; see this post of mine for a few pictures. Not sure about the bolt spacing though, didn't take any measurements when I was cleaning mine.
    #1: 1979 GS 550 EC "Red" (Very first Bike)     New here? ☛ Read the Top 10 Newbie mistakes thread
    #2: 1979 GS 550 EC "Blue" "Rebuild" thread     Manuals (and much more): See Cliff's homepage here
    #3: 2014 Moto Guzzi V7 Racer

  10. #10
    Join Date
    Mar 2009
    Location
    Newport News, Virginia
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    Default

    This one might be interesting to you then. I was hoping it would fit mine but my measuring method was off a bit the first time and mine was 50mm. https://www.z1enterprises.com/petcoc...0h-kz750h.html
    '78 GS1000E, Dyna-S ignition, Dyna Green Coils, K&N pods, Delkevic SS 4-1 exhaust, Dynojet Stage 3 jet kit, Russell SS Brake Lines, Progressive suspension, Compu-Fire series Regulator 55402 and Advmonster cree LED headlight conversion.

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