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    #1

    Petcocks question

    I have a 1979 Yamaha XS750 also and it also has vacuum petcocks. I am aware of the problem that yamaha bike owners have with the petcocks if they fail, then fuel can go down the vacuum lines and into the oil in the motor. This is a major problem if it occurs. Question is does my 1981 suzuki GS1000G have this problem if the petcocks fail on it or is it a different setup where something like this will not occur.
    I know if you leave ur petcocks to on after you shut ur motor off it is possible if the valve in the carb is bad the weight of the fuel in the tank can overcome that carb valve and leak fuel through the carbs down into the piston camber area and then leak past the rings into the oil resulting in the same problem..Can anyone answer this question. Also was this just a Yamaha problem or did any other UJM have this problem???
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    #2
    Hi,

    Yes, malfunctioning vacuum petcocks on these classic GS bikes have the same issues; gasoline in the oil, fuel in the cylinder/hydro lock, #2 plug fouling, etc. After installing new float valve seats in the carbs and a new petcock you won't have to worry about it for another 25 years or so.

    Thank you for your indulgence,

    BassCliff

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      #3
      in my epic struggle to get my bike idling correctly :S I recently pulled the tank off and used a syringe in the gas line to try to adjust the idle. Of course, the vacuum port is open, but when I put my finger near said port, I feel air blowing out, not sucking in. Strange then that it's called a vacuum port.

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        #4
        As Cliff says, just about all these old UJMs will suffer from these problems from time to time.

        Having owned Yammies I ran into this with my 400, 500 Virago and XS 650. With the 400, I got a used one that worked ok. The Virago I rebuilt but I wasn't happy with it as it did leak from time to time thereafter. The 650 had two petcocks and for some reason they seemed to alternate leaking. I rebuilt them but the problems persisted to the point where I decided to junk them and go with one single manual "Pingle" style cock. That fixed it. the only problem with them is that you have to remember turning it off and on.

        Vacuum taps are really convenient but they all seem to break down at some point. I guess they can be rebuilt but I've never had any real luck with that. For me, I think, if I couldn't get a factory fresh one, I'd go with the manual.

        As Cliff also mentions, its important to make sure your float valves are working correctly as well and I've had that problem as well.

        Hopefully a clean and rebuild would work for you.

        Cheers,
        Spyug

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          #5
          So I guess pull the tank and set it up over some newspaper to see if it leaks on the paper for probably a half a day and if that does not happen ur probably pretty safe for now and then just keep a check on ur oil levels. Thats abt the only way...I can think of and if they do leak rebuild the petcocks. Do they still make a good rebuild kits for GS1000G 1981 model? Also these things can also leak through the vacuum tube as well as the gas line? Thanks for the responses from all....

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            #6
            does anyone recommend a new manual petcock and what size is the openning on a 81 gs1000g? i think im going to go ahead an put manuals on my scooter. im thinking abt pingel petcocks

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              #7
              oh one more thing does suzuki still have replacement originals for sale and rebuild kits?

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                #8
                Hi,

                Many members have used the Pingel aftermaket parts with success, as long as they don't forget to turn them off. I think your bike uses the standard 41mm spacing.

                Try Z1 Enterprises for a new OEM style petcock and new gasket/o-ring. They are a bit cheaper than original Suzuki petcocks. If Z1 doesn't have one, there are dozens of OEM vendors listed in your "mega-welcome".

                A few members have had luck with petcock rebuild kits, but they are not widely recommended. Just buy a new one and be done with it.


                Thank you for your indulgence,

                BassCliff
                Last edited by Guest; 06-07-2010, 11:08 PM.

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                  #9
                  vacume petcock on xs750 yuk!!

                  i,ve got a re-worked modded xs650 and its got 2 nice non vacume petcocks they are both manual petcocks ,,, never ever had a problem throw the vacume up the road and go manual you will find hundreds on ebay.com hope this helps you regards david

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