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  1. #11
    Moderator OsideBill's Avatar
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    Quote Originally Posted by mrtinker View Post
    I've just rebuilt carb on 99'xl1200ltd and I've got a question about the two different pressures that the n/s seem to be lifting at. Let me describe, I'll try to be brief but thorough....

    I am testing for about 42-43 psi pop-off with a 95g spring and 1.5 N/S. (I don't think the hi/lo jets matter do they? or the #turns i've set the t-handles to?)

    I've connected hoses to the inlet/outlet ports on the pump body and blocked off all but one inlet which is connected to my test gauge which is then connected to isolation valves and then through a regulator from my pressure supply. (I'm actually using nitrogen instead of compressed air-this shouln't matter should it?)

    I'm spraying wd-40 all over the n/s (& manually depressing the arm so as to get wd40 under it too) and jets side of the carb and am also spraying it in the inlet hose before I start charging the inlet to perform the test. What I'm finding is when it initially lifts (about 50psi) only for a quick spurt and then holds pressure fine. Then as I continue the test, it must be pushing the wd-40 out of the inlet hose and it starts lifting right at about 43psi. Its just that first initial lifting that is around 50 psi, the next 3-4 times it lifts @ 43psi before all the wd40 sprays out of everything and that's extent of my test. I've taken about 3/4 of a turn off the 95g spring to get it to lift at these pressures so far, It started at around 65psi before I cut it down.

    Is this okay? Do I go by the very first time it lifts with the liquid in the inlet hose (50psi) or the readings that follow and its lifting at the 43psi? Or do I continue cutting the spring until I get the initial lifting down to 43psi?

    Thanks for reading all of this and keeping me straight guys!
    If it started at 65 something is not right. The hose should be connected to the fuel inlet and all the others blocked off.


  2. #12

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    Hey Bill,

    I just did the next carb and same outcome. I do have the inlet connected to the pop-off gauge set-up and all the other ports blocked off. Had to cut about the same amount off the 2nd carb's 95g spring. Do u think that they sent me the wrong springs? These are kind of a dull silver or greyish color. The ones in the Mikuni rebuild kits (I didn't use) are a bright silver.

    Any suggestions?

  3. #13
    Moderator OsideBill's Avatar
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    I do know they make a different spring for the Sea Doos not sure if it is longer. as long as you get them all the same, that is the key. Dull silver is the correct color.

  4. #14

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    pop off pressure question....continued


    Hey Bill...

    Third carb turned out the same way.... had to trim about 7/8ths of a turn to get the third carb to initially lift @ 50 psi, then 43psi until all the wd40 blows out everywhere.

    Am I done?

    Or do I need to keep cutting till the initial lift is closer to 43psi?

  5. #15

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    I got a gp1200r with Miller heads (42.5 domes/120compression), rad flywheel,protec pipe, f/a,
    cant get the carbs set just right. runs good at top end for 10sec. then it drops down to 5500rpm for 3sec.

    carbs settin
    120 low
    135main
    n/s 1.5
    dont know what spring i am going with

    what should the popoff presure be?
    i was told around 23psi

  6. #16
    Moderator OsideBill's Avatar
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    The chart on page one answers the questions. But this is not a pop-off problem it occurs much earlier in the power band. What you are describing is a rev limiter issue. what RPMs ais this shutting down at? sounds like the limiter is kicking in and shutting down the power valves, which is by design to keep the motor from blowing when you come unhooked.

  7. #17

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    so im trying to figure out how you work out what size jets and springs to use . I have a gp1200r with tripple pipes novi 48carbs r and d ecm vf3 reeds 150psi riva heads and pro x pistons what size jetting specs should i be using i am at sea level. Like to initially do the test do you have the spring removed and just put the tester on and see what psi reading the needle lifts off the seat ? and say if it lifts off at 55psi do i then go right it needs a 155gram spring and a 1.5 jet or am i way off course someone please help cos i really want to know how to do this so i can tune my ski properly without running it to lean

  8. #18
    Yamaha artisan Cutlass's Avatar
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    No. You measure pop off pressure with the spring installed. The chart gives you a rough idea of what the pressure should be, when you use a certain spring and needle combo. Its important to test and make sure they are close and that all 3 carbs are within a few psi of each other.

  9. #19
    Moderator OsideBill's Avatar
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