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  1. #1

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    Tuning Keihin carbs with 3 circuit jettings?

    I am familiar with tuning the traditional 2 circuit (low & high) jettings and pop-off pressures, but im new to tuning these Polaris carbs with 3 jetting circuits. Ive always kind of viewed the pop-off pressure as the transition stage and mid-range as one. But now im faced with 2 variables in pop-off pressure and a mid-range jetting which screws up my thinking.
    First and foremost, I am using carbs from a 2001 Polaris SLX on a Kawasaki Ultra 150. The carbs are mounted and now running on the trailer but i wont dare run it on the water under load without some advice on jettings. I realize i am on my own on this as Ive found only 2 other people that have done this very same mod on their Ultra 150, one is from a very old post and is no longer active on the forums, and the other did it years ago and cant remember what jets he ran. I imagine the jets will be kind of close from stock as both skis are 1200cc with roughly similar horsepower. Im looking for suggestions as a starting point to begin my tuning, so dont be shy If things go wrong i wont blame anyone but myself. Also suggestions for tuning the mid-range circuit. How do i differentiate between the pop-off or the jet needing adjustment?


    Things to keep in mind
    -Polaris 1200 = 1165cc, 135hp, with a bore x stroke of 84x70
    -Kawasaki 1200 = 1176cc, 145hp, with a bore x stroke of 80x78
    -Choke plates have been removed
    -Accelerator pump is retained unless someone can tell me that its better to disable it.
    Last edited by Spades; 11-26-2014 at 05:07 PM.


  2. #2

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    How did it turn out for yA?

  3. #3
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    First thing I would do is get a good tach. That can tell you a lot. What are you using for a Flame arrestor? I would guess that the stock Polaris settings would get you somewhere in the ball park. I would keep the accel pump if you can. The tuning instructions that Mikuni has are a good place to start. Run the ski in the various throttle ranges and see what it does. Your ear and the tach will tell you what to do.

  4. #4
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    does the intake still have the connecting passages between cylinders?

  5. #5

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    Wow, i didnt think anyone ever replied to this thread, I figured everyone was gone for the winter I havent ran it on the water yet, but its getting warm enough to take it out real soon here

    No Flame arresters at the moment, but will use triple K&N. And the balance tube is left in place for now, im debating if its better to plug it since they dont exist on Polaris skis

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Spades View Post
    Wow, i didn't think anyone ever replied to this thread...
    Tip: Click on the Thread Tools link above, then click Subscribe to this Thread

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  7. #7
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    balance tube was part of the reason for constant velocity carbs.acts like bigger carb down low and keeps the reasonable fuel usage up top.i believe the guys were replacing the intakes with non balance tube ones.

  8. #8

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    I should have mentioned that i rejetted them due to the choke plates removed & flame arresters. I went with

    Low: from 70 to 75
    Mid: from 42 to 50
    High: from 140M/142C/135P to 155 all

    Do you think i overdid it?

  9. #9
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    the mains were probably all that need to be done and staggered up to 145 across the board if the kawi is jetted straight across the mainsas well,do the kawi's have high speed adjusters and are they all the same setting?

  10. #10

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    The Ultra-150 only has pilot screw adjustment, no hi speed adjust.

    For comparison, Ultra-150 OEM jet specs are:
    Lows: 48
    Highs: 165

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