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  1. #1

    Gp 1200 Carbie Questions 99 model

    Hello guys,

    Just about to rebulid my carbs and was wondering what is the stock pop off pressure and the stock needle and seat required?


  2. #2
    Moderator OsideBill's Avatar
    Join Date
    Mar 2006
    United States
    Here is a link to the service Manual for the GP if you do not have one.
    the OEM needle and seat is 1.2 the manual does not give pop off pressure as a check.

    also here is a link to the Mikuni SBN Manual

  3. #3
    Thanks for that. I already had them but couldnt find that information in there.

  4. #4
    qbzonk's Avatar
    Join Date
    Aug 2006
    check this thread:

    Be sure to check the needle and seat for size. My GP800 was supposed to have a 1.2 needle valve, but after closer inspection, the previous owner installed a 2.3.

    From what I got, the pop-off pressure is determined by the color/weight of the pop-off arm spring. The chart on the above link shows what the pop-off should be for each different spring. What spring is good for you depends on your mods and how the ski is running.

  5. #5
    Moderator OsideBill's Avatar
    Join Date
    Mar 2006
    United States
    I run 1.5 N&S with Black Spring 38psi pop off on my 99 GP

    But this still does not answer the question as to stock pop off. if I remember right stock was around 45 psi I am sure someone will chime in with correct answer.

  6. #6
    Thanks for that. My ski is stock as a rock. Trying to get it to run right before I do anything.

  7. #7
    Just had a look at the carbie manual. It doesn't cover the 1.2 needle and seat pressure??

  8. #8

    Pop Off pressure

    Hi everyone,

    Just had a chat to a local shop over here in Australia and they are telling me that the stock pressure should be around 70-75 psi with the standard needle and seat of 1.2. Mine at the moment is around 63 psi. Does this sound right. And another thing I found out today was my carbs leak fuel at idle through the venturi indcating pop off pressures too low? Anyone got any ideas? Does this sound right?


  9. #9
    cheatin' piston popper addicted's Avatar
    Join Date
    Jul 2006
    north jersey
    popoff on the 1200 carbs that I put on my raider was 51. They had a 1.2 seat. not sure of the spring.

    If you are dribbling at that high of a popoff, your n&s need to be replaced, or the o-ring on the seat is leaking. Also check the flaps under the kidney shaped block the covers the jets. You can double up on them if needed. Lastly, check the gasket under the reed blocks. If they are blown out under the crossover passages, you can have problems.

  10. #10


    Thanks for that.

    So new needles and seats (1.2) are on there way but the pop off pressure? Should I set it up stock (70 -75psi) or back it off abit to around 60psi?

    Any thought?


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