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Another wierd fault diagnosed...

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  • brianposullivan
    Hi all, Well I seem to be going through a series of faults at the moment - these are probably a hang-up from the fact that the previous owner rode 500 miles in
    Message 1 of 11 , Mar 1, 2003
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      Hi all,
      Well I seem to be going through a series of faults at the moment -
      these are probably a hang-up from the fact that the previous owner
      rode 500 miles in 2 years, and I've put on 20,000 miles in the
      following 2 years. Plus it was an American import - so it's been
      freighted twice - and was probably manufactured well before its 1999
      reg... I still love the thing to pieces - 2 years and I'm still
      completely in love with my TBS!

      ...anyway, these are the symptoms:

      On a full tank of petrol I can enjoy a spirited ride, sprinting up to
      80-90mph for about 30 mins before the bike will start to stutter - it
      feels like it's running short on petrol on 1 cylinder. If I stop, the
      engine quickly stops stuttering. But I normally just slow down to
      50mph - and within a minute it stops stuttering.

      On a half-tank of petrol, I can cruise gently at 70mph until the
      reserve - any faster and it stutters. Once onto reserve, 50mph is the
      max speed...

      I'm pretty sure I've got a stuck float valve in one, or maybe more,
      of my carbs...

      Anyway, given that carbs are such sensitive devices, what's the best
      approach? I'll obviously be removing the whole set.
      -Is WD-40 a suitable cleaning solution?
      -Will they need to be re-balanced afterwards?
      -Any other tips?

      Cheers,
      Brian
    • petermholmes
      Hi Brian, ... Before I pulled the carbs I d pull the fuel tap out of the tank and make sure that its filter is clean and that the tank doesn t have any sludge
      Message 2 of 11 , Mar 1, 2003
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        Hi Brian,

        > I'm pretty sure I've got a stuck float valve in one, or maybe more,
        > of my carbs...
        >
        > Anyway, given that carbs are such sensitive devices, what's the best
        > approach? I'll obviously be removing the whole set.
        > -Is WD-40 a suitable cleaning solution?
        > -Will they need to be re-balanced afterwards?
        > -Any other tips?

        Before I pulled the carbs I'd pull the fuel tap out of the tank and
        make sure that its filter is clean and that the tank doesn't have any
        sludge accumulated in the bottom of it. Does anybody know if the
        Keihins have filters on their end of the gas line like Amals have? If
        they do, I'd clean those too. I'd also probably run at least a tank
        or two of fuel system cleaner through the bike before I declared the
        carbs to be dead and went to all the trouble of digging into them.
        Pulling a carb these days isn't exactly the 90 second job it used to
        be.

        Good luck with it. Let us know what you find.

        Peter
      • brianposullivan
        ... any ... whoops... should have mentioned that I ld already pulled and cleaned the fuel tap - there was a little sludge at the bottom of the tank, but that s
        Message 3 of 11 , Mar 2, 2003
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          --- In triumphthunderbirdsportriders@yahoogroups.com, petermholmes
          > Before I pulled the carbs I'd pull the fuel tap out of the tank and
          > make sure that its filter is clean and that the tank doesn't have
          any
          > sludge accumulated in the bottom of it.

          whoops... should have mentioned that I'ld already pulled and cleaned
          the fuel tap - there was a little sludge at the bottom of the tank,
          but that's gone now... the tap however was clean.

          ...although I haven't given any thought to a carb cleaner - I'll go
          and get some and see if that clears it: I've had this fault for a
          couple of months now (it took that long to discover that it was
          linked to speed AND level of fuel in the tank) so I'm absolutely
          certain its a stuck float... all the facts point to it (related to
          fuel height AND speed - plus it only loses fuel one pot not all) but
          you're absolutely right - if a carb cleaner can shift it, that'll
          save a lot of effort removing carbs...

          Cheers,
          Brian
        • petermholmes
          ... If you do have to pull the carbs, I ve never had any problem using kerosene to clean the fuel bits. That s exactly what I do every few years to make sure
          Message 4 of 11 , Mar 2, 2003
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            > ...I'm absolutely certain its a stuck float

            If you do have to pull the carbs, I've never had any problem using
            kerosene to clean the fuel bits. That's exactly what I do every few
            years to make sure that the Metralla's still running. Pull the Amal,
            pop off the bowl cover, soak everything in kerosene for a couple of
            days while agitating occasionally, replace the bowl cover, mount it
            back on the bike and fire her up.
          • tbs_boy
            While you re trying stuff, you might want to pull off the vent hose from the rear of the tank and see if the problem subsides. Unlikely, but if that s the
            Message 5 of 11 , Mar 2, 2003
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              While you're trying stuff, you might want to pull off the vent hose
              from the rear of the tank and see if the problem subsides. Unlikely,
              but if that's the only issue, it would also save lots of cleaning
              time.

              Assuming you may need to go down the carb cleaning path, I saw an
              interesting letter in this month's Rider magazine which suggests
              using the ultrasonic jewelry cleaning solution on carb parts to clean
              them. This guy claims he bought a kit from Walmart and had great
              luck cleaning up 10 year old gummed up carb parts, so I may try it
              when the carbs call for a cleaning again.

              Good luck anyway,
              Tom P.


              --- In triumphthunderbirdsportriders@yahoogroups.com, brianposullivan
              <no_reply@y...> wrote:
              > --- In triumphthunderbirdsportriders@yahoogroups.com, petermholmes
              > > Before I pulled the carbs I'd pull the fuel tap out of the tank
              and
              > > make sure that its filter is clean and that the tank doesn't have
              > any
              > > sludge accumulated in the bottom of it.
              >
              > whoops... should have mentioned that I'ld already pulled and
              cleaned
              > the fuel tap - there was a little sludge at the bottom of the tank,
              > but that's gone now... the tap however was clean.
              >
              > ...although I haven't given any thought to a carb cleaner - I'll go
              > and get some and see if that clears it: I've had this fault for a
              > couple of months now (it took that long to discover that it was
              > linked to speed AND level of fuel in the tank) so I'm absolutely
              > certain its a stuck float... all the facts point to it (related to
              > fuel height AND speed - plus it only loses fuel one pot not all)
              but
              > you're absolutely right - if a carb cleaner can shift it, that'll
              > save a lot of effort removing carbs...
              >
              > Cheers,
              > Brian
            • pickwickian51@aol.com
              Does anybody know if the Keihins have filters on their end of the gas line like Amals have? The parts catalogue shows that there is one (1) fuel screen. In the
              Message 6 of 11 , Mar 2, 2003
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                Does anybody know if the
                Keihins have filters on their end of the gas line like Amals have?

                The parts catalogue shows that there is one (1) fuel screen. In the drawing
                it is positioned between the center and left carburettor. IIRC from the
                Haynes manual is is at the end of the main fuel line from the tank.

                Just to be safe, have you check that tip-over valve that most of us have lost
                or removed? And, your fuel cap? Check to make sure it's venting as well.

                Aloha and Happy Trails,

                Gary Gavin
                98 Thunderbird Sport
                02 Mini Cooper


                [Non-text portions of this message have been removed]
              • brianposullivan
                ... ...yep - I had that problem this summer: I had to replace a snapped throttle cable, and I mis-routed the relief valve when putting everything back
                Message 7 of 11 , Mar 2, 2003
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                  --- In triumphthunderbirdsportriders@yahoogroups.com, tbs_boy
                  <no_reply@y...> wrote:
                  > While you're trying stuff, you might want to pull off the vent hose
                  > from the rear of the tank and see if the problem subsides.

                  ...yep - I had that problem this summer: I had to replace a snapped
                  throttle cable, and I mis-routed the relief valve when putting
                  everything back together: This caused a vacuum in the tank - but
                  that's been rectified.

                  In this instance, the engine is only losing one pot, not all of them:
                  And there's definitely no vacuum being developed - if i pull the tank
                  cap, there's no tell-tale hiss.

                  Thanks for the suggestion though! it just goes to show I'm having a
                  run of faults at the moment...

                  Cheers,
                  Brian

                  PS. to those in the UK - what a wonderful day we had today: It's
                  warm, and the recent rain has cleared salt from the roads: We have
                  grip again!
                • jcatbert45
                  ... I recently noticed that my dealer tossed mine out; would have been nice if they mentioned that to me. My regular mechanic was at Ducati school in Fl,
                  Message 8 of 11 , Mar 3, 2003
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                    >Just to be safe, have you check that tip-over valve that most of us
                    >have lost or removed? And, your fuel cap? Check to make sure it's
                    >venting as well.
                    >

                    I recently noticed that my dealer tossed mine out; would have been
                    nice if they mentioned that to me. My regular mechanic was
                    at "Ducati" school in Fl, when I picked up my bike so I guess I will
                    give them the benefit of the doubt.

                    I did manage to do a 10 mile spin on the T-Bird this weekend. It was
                    a balmy 42 degrees. The T-Bird started up pretty quickly, a little
                    sputtering, but I had let the carb's run dry. It ran pretty smoothly
                    and without hesitation once warmed up. Tires needed no air
                    (surprising after 2-3 weeks of sitting). The winter weather seems to
                    have taken it's toll on her though ;( <sniff>. Hope the oxidation
                    buffs out easily. I rubbed some WD-40 on the chrome wheels; they
                    look good. Can't wait to be able to wash and polish. Soon I hope,
                    but 13 degrees F this AM! Sometime soon as temps will be moderating
                    later this week.

                    - Jerry
                  • brianposullivan
                    Hi all, I m still trying to diagnose a wierd misfire/fuel starvation fault and I ve eliminated a lot of possible root causes and I m basically left with gumbed
                    Message 9 of 11 , Mar 19, 2003
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                      Hi all,
                      I'm still trying to diagnose a wierd misfire/fuel starvation fault
                      and I've eliminated a lot of possible root causes and I'm basically
                      left with gumbed up carbs or/AND a dying coil.

                      I know the carbs have some dirt, because added some REDEX (fuel
                      cleaning additive) for 1 tank - and when I drained the carb float
                      bowl then was a small, but significant quantity of very fine, silty,
                      rust.

                      To help eliminate the dying coil I like to know how your tacho
                      needles behave on your TBS'es.

                      Is it rock solid at about 4500RPM, or does it tremble?

                      Mine trembles by as much 400RPM which may indicate a dying coil, or
                      they may all be like that... only you can say!

                      Regards,
                      Brian
                    • macboots
                      Brian - I ve experienced fluctuations on my tach at higher RPMs that fit your description. - Will ... silty,
                      Message 10 of 11 , Mar 19, 2003
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                        Brian -

                        I've experienced fluctuations on my tach at higher RPMs that fit your
                        description.

                        - Will

                        --- In triumphthunderbirdsportriders@yahoogroups.com, brianposullivan
                        <no_reply@y...> wrote:
                        > Hi all,
                        > I'm still trying to diagnose a wierd misfire/fuel starvation fault
                        > and I've eliminated a lot of possible root causes and I'm basically
                        > left with gumbed up carbs or/AND a dying coil.
                        >
                        > I know the carbs have some dirt, because added some REDEX (fuel
                        > cleaning additive) for 1 tank - and when I drained the carb float
                        > bowl then was a small, but significant quantity of very fine,
                        silty,
                        > rust.
                        >
                        > To help eliminate the dying coil I like to know how your tacho
                        > needles behave on your TBS'es.
                        >
                        > Is it rock solid at about 4500RPM, or does it tremble?
                        >
                        > Mine trembles by as much 400RPM which may indicate a dying coil, or
                        > they may all be like that... only you can say!
                        >
                        > Regards,
                        > Brian
                      • pickwickian51@aol.com
                        I have to add my two tach replacements under warranty to the list. At 4.5k the first needle stopped and then jumped to 5k. The second moved wildly from 4 to
                        Message 11 of 11 , Mar 19, 2003
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                          I have to add my two tach replacements under warranty to the list. At 4.5k
                          the first needle stopped and then jumped to 5k. The second moved wildly from
                          4 to 5k. The current one has done well and been steady until recently (which
                          may be in the past year) it wobbles a bit at the 4.5k mark again.

                          BTW, did your dealers replace just the tach or the whole set. Mine replaced
                          the whole set, twice and didn't note my mileage on the work order (they did
                          all the other times it was in for service) so I've been guessing on my total
                          mileage. I'm confident that I've been underestimating it.


                          As for the coil problem, and as Alec says:

                          > In your case, sound like you cannot start investigating the coil possibility
                          > until you are satisfied you have cleaned up the fuel system 100%.
                          >
                          >

                          My tank is being cleaned and sealed (hope it's finished by this weekend)
                          after it was discovered that I too had small rust particles in the bowls.
                          I've been experiencing some bogging that at first was consistent with float
                          height adjustment but later moved around the rpm range. I was slowly trying
                          to track down the problem and learn something but got really frustrated when
                          the bike would stall at times starting from a stop. It also would idle smooth
                          and then at times get into a rhythm that was more like one or more cylinders
                          were not firing.

                          Rusting fuel tank reports have been more frequent with the other model
                          classics so it wasn't a complete surprise.


                          Aloha and Happy Trails,

                          Gary Gavin
                          98 Thunderbird Sport
                          02 Mini Cooper


                          [Non-text portions of this message have been removed]
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