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  1. #1
    hitman's Avatar
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    GP Stock Jetting

    Does anyone know the numbers of the stock main jets on the carbs of a 99 GP1200? They're Mikuni 44s I believe. I am rebuilding them and removing the choke plates for a primer kit. I also premix. Becasue of this, the tech I spoke to reccomended I step the jets up one number.

    Hoping I can get away without having to mess with the pop-off pressure but you GP gurus let me know what you think...
    Last edited by hitman; 06-19-2007 at 01:21 PM.


  2. #2
    oldmanraider's Avatar
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    Hitman, come on over to the oldschool section and play.

    The GP1200 stock jets are 135m and 100p(1) 95p(2) 97p(3)

  3. #3
    cheatin' piston popper addicted's Avatar
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    welcome! search the yami section. there is a post with the gp manual on pdf. save yourself the $50 bux.

  4. #4
    DAGO RACING CREW 97GPSLEEPER's Avatar
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    There is no need in changing jet sizes when removing the choke plates. The additional air flow from the choke plates being removed can be compensated by richening the mixture screws. A half a turn counter clockwise will most likely be plenty.

  5. #5
    Moderator OsideBill's Avatar
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    Mains are 135 I am with everyone else no need to change the mains

  6. #6
    hitman's Avatar
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    Guess I need to get with the program. Didn't really think the GPs were "old school" quite yet.

    Thanks for the info guys. I'll try richening it up a bit and will leave the main jets alone. I looked in the manual and didn't stumble across the jet sizes. I was pretty sure all the mains were the same. Now that I think of it I wasn't looking in the ski manual. I was looking in the Mikuni manual.
    Last edited by hitman; 06-18-2007 at 04:57 PM.

  7. #7
    hitman's Avatar
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    So since the stock main jets are 135s you guys don't think I could just step them up to 137.5s and start with one turn out on the highs and lows and go from there?

  8. #8
    DAGO RACING CREW 97GPSLEEPER's Avatar
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    No, just open up the mixture screws, no need to rejet.

  9. #9
    Moderator OsideBill's Avatar
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    The Pilot jets are stagered mine are #1 92.5 #2 95 #3 97.5 the best results I found to richen it up a bit was to make my pilots all 100 and up my needle and seat from 1.2 to 1.5 and change to gold (115 gr) spring. I left mains at 135 I did run the dull silver (95 gr) spring first but it dribbled a bit so I changed to the gold.

  10. #10
    hitman's Avatar
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    Quote Originally Posted by osidebill View Post
    The Pilot jets are stagered mine are #1 92.5 #2 95 #3 97.5 the best results I found to richen it up a bit was to make my pilots all 100 and up my needle and seat from 1.2 to 1.5 and change to gold (115 gr) spring. I left mains at 135 I did run the dull silver (95 gr) spring first but it dribbled a bit so I changed to the gold.
    Out of curosity, what all do you have done to your 99 GP and what's it GPS? I am seriously thinking of just overhauling my bike to make it porpoise less and run a bit faster.

    I'd be fine with 65-67 on GPS.

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