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Bike "runs out of gas" even with a full tank.....

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    #1

    Bike "runs out of gas" even with a full tank.....

    I am having a very confusing problem ( problems ? ) with my 1980 GS850G. I recently rebuilt my carbs with K&L rebuild kits and the bike runs much better now, MOST of the time.

    Sometimes it runs GREAT !

    Sometimes it runs like it?s only running on 2 or 3 cylinders.

    Sometimes it runs out of gas, even though the gas tank has PLENTY of fuel in it and even when full?.. The fuel filter will be completely empty and dry. I can remove the hose from the filter and the fuel flows without a problem from the tank but when I re-attach the hose to the filter, the flow trickles to a stop. Could the carb fuel needles be sticking closed ? Removing the fuel cap has no effect when this problem arises either, so I am sure it is venting properly. When it runs dry like this, the only way I can get fuel flowing again is to turn the petcock to PRIME and put the bike on it?s center stand and rock the hell out of it until the fuel starts flowing?? At first I thought the petcock was plugging up, but when I removed it to check, it was fine.

    Another theory I have is this??. The fuel hose coming from the petcock has to go UP before turning back down, could it be getting a ?bubble? in the line and vapor or hydro-locking and not flowing ? Because, as I said above, when I remove the hose from the filter or petcock, it flows like a river !

    I am contemplating using a SMALL low-pressure fuel pump to see if this might alleviate the problem(s). Has anyone ever done this ? Will the needles stand up to 3-5psi of continuous fuel pressure or will I be flooding my motor ?

    Any ideas/suggestions/input will be GREATLY APPRECIATED !

    THANK YOU !
    -D Payne
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    #2
    The first thing I'd do is make a new line that doesn't have a filter and goes downhill all the way. You will lose any fuel capacity that is below the upper most part of the fuel line. Fuel filters can be real hassle as I've found out. If your tank is clean you shouldn't need one.

    Steve

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      #3
      Originally posted by srivett2
      The first thing I'd do is make a new line that doesn't have a filter and goes downhill all the way. You will lose any fuel capacity that is below the upper most part of the fuel line. Fuel filters can be real hassle as I've found out. If your tank is clean you shouldn't need one.

      Steve
      This is true, especially if you are using an automotive type paper element. I've run the ones with a brass filter before with no problems, but I not sure how much the actually filter out.

      Comment

        #4
        There is a filter screen on the petcock inside the tank and there are four more in the carbs (1 in each float bowl). I dont think there is anything to be gained by having and inline (6th) filter in addition to the stock five. Generally, the small inline filters will not flow enough fuel in a gravity feed system such as as motorcycles. NO, the float needle seals will not tolerate a fuel pump and 4 or 5 lbs of pressure. Max pressure for the needles is aprox 1 psi.

        Earl
        Komorebi-The light filtering through the trees.

        I would rather sit on a pumpkin and have it all to myself than be crowded on a velvet cushion. H.D.T.

        Comment

          #5
          This sounds liek the problem I had with my bike. Check your gas cap. It may not be venting properly. Or when it happens next, open up your gascap and see if fuel flows again.
          You'd have to be crazy to be sane in this world -Nero
          If you love it, let it go. If it comes back....... You probably highsided.
          1980 GS550E (I swear it's a 550...)
          1982 GS650E (really, it's a 650)
          1983 GS550ES (42mpg again)
          1996 Yamaha WR250 (No, it's not a 4 stroke.)
          1971 Yamaha LT2 (9 horsepower of FURY.)

          Comment

            #6
            C7Z, sounds like a failing vacuum line to the petcock, or the petcock's diaphragm/spring assy' is not functioning correctly.
            And on the seventh day,after resting from all that he had done,God went for a ride on his GS!
            Upon seeing that it was good, he went out again on his ZX14! But just a little bit faster!

            Comment

              #7
              There is a filter screen on the petcock inside the tank and there are four more in the carbs (1 in each float bowl).
              Agreed. There is no need for a 6th inline filter. I have used them and they caused me nothing but grief.
              Currently bikeless
              '81 GS 1100EX - "Peace, by superior fire power."
              '06 FZ1000 - "What we are dealing with here, is a COMPLETE lack of respect for the law."

              I ride, therefore I am.... constantly buying new tires.

              "Tell me what kind of an accident you are going to have, and I will tell you which helmet to wear." - Harry Hurt

              Comment

                #8
                when you say it sometimes runs on 3 cylinders. It the failing cylinder #2??

                Comment

                  #9
                  Problem Solved ?

                  Thanks for all the suggestions folks, but I think I MIGHT have found the problem....

                  When I rebuilt the carbs, I used new fuel hose from the petcock to the carbs and I used plain-old 8mm fuel hose..... Apparently the new hose was kinked where it made the turn down into the carbs.... I replaced the regular fuel hose with EFI rated 8mm hose and it seems to hold it's shape better in the bends. So far after 30 miles of riding, it hasn't missed a beat and it runs like new. I hope I am not premature in declaring it as "problem solved", but so far, so good !

                  Thanks again !
                  -D Payne

                  Comment

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