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1200 Carb Diaphragms!

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  • Alec Gore
    You may recall that in June/July I wrote about my 1200 s performance being less than might be expected, especially at the top end. I d tidied up the fuel
    Message 1 of 5 , Oct 31, 2006
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      You may recall that in June/July I wrote about my 1200's
      performance being less than might be expected, especially at the
      top end. I'd tidied up the fuel lines, put in a K&N filter in
      the stock airbox and fitted Staintunes. The bike had been
      serviced, which included new plugs. Still I thought it wasn't
      "quite there". Thought the petcock vacuum might be playing up,
      as it does on low tank of fuel.

      Took it along to PDQ www.pdq1.co.uk for a dynorun this morning,
      thinking that some minor tweaking was in order. What a shock! 3
      out of 4 carb diaphragms were perished/holed. And the holes
      weren't near the edges where damage could have been caused by
      catching them in the cap threads. The tech said the carbs had
      probably never been apart before. This was plain and simple
      deterioration through wear. If it wasn't, they were from a bad
      batch or something has eaten away at them.

      I know my bike was stood for about 18 months in a showroom
      before I bought it and had fuel additive (Reddex) added to the
      petrol to stop the carbs getting sticky, but I presume that
      stuff doesn't corrode carb rubber.

      Anyway, another item to add to the list of possibilities when
      your bike is running less than crisply throughout the rev range,
      but particularly at the top end.

      Regards

      Alec


      [Non-text portions of this message have been removed]
    • Tom
      ... Alec, Good to hear that the shop was able to help. When they complete the repairs, and perform the dyno-runs, please post a follow up note. Tom D.
      Message 2 of 5 , Oct 31, 2006
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        --- In TriumphTrophy@yahoogroups.com, "Alec Gore" <e-mail@...> wrote:
        >
        > Took it along to PDQ www.pdq1.co.uk for a dynorun this morning,
        > thinking that some minor tweaking was in order. What a shock! 3
        > out of 4 carb diaphragms were perished/holed.
        > Regards
        >
        > Alec

        Alec,
        Good to hear that the shop was able to help. When they complete
        the repairs, and perform the dyno-runs, please post a follow up note.

        Tom D.
      • malcpowe@aol.com
        Alec, thanks for the info. Malcolm [Non-text portions of this message have been removed]
        Message 3 of 5 , Oct 31, 2006
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          Alec, thanks for the info.

          Malcolm



          [Non-text portions of this message have been removed]
        • Alec Gore
          Back to better than ever! This is an 03 1200 with K&N filter and Staintunes fitted. You can clearly see the sweet zone between 5-7K. Max torque is 76 ft-lbs.
          Message 4 of 5 , Nov 2, 2006
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            Back to better than ever! This is an 03 1200 with K&N filter and
            Staintunes fitted. You can clearly see the "sweet zone" between
            5-7K. Max torque is 76 ft-lbs. Max horse power is 104 hp at
            8.5K. Remember, these are rear wheel figures.

            I don't know over what period the 3 diaphragms had gradually
            deteriorated, but you can see from the dyno the dramatic loss of
            power when compared to how it should be. The bad run in blue is
            before the diaphragms were changed - max was less than 40 hp!

            http://www.alecgore.com/trophydyno.jpg

            And guess what? I left the dyno centre on only a cupful of fuel,
            which normally would have caused all sorts of spluttering. Now,
            no problems because the vacuum to the fuel tap is sufficient to
            allow even the last amount of fuel in the tank to flow.

            Happy days are here again :-)

            Regards

            Alec
          • Tom
            ... only a cupful of fuel, ... And know, one more item to check if you have a fuel starvation problem!!! Thanks Alec
            Message 5 of 5 , Nov 3, 2006
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              --- In TriumphTrophy@yahoogroups.com, "Alec Gore" <e-mail@...> wrote:
              >
              > Back to better than ever! > And guess what? I left the dyno centre on
              only a cupful of fuel,
              > which normally would have caused all sorts of spluttering. Now,
              > no problems because the vacuum to the fuel tap is sufficient to
              > allow even the last amount of fuel in the tank to flow.
              > Regards
              >
              > Alec


              And know, one more item to check if you have a fuel starvation
              problem!!!

              Thanks Alec
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