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  1. #1

    stock jetting on 1999 GP1200 with the 1.5 seat not the 1.2 - stock airbox

    Can someone provide stock jetting specs and settings for a GP1200 using the 1.5 seats, 115g springs for 55psi pop-off, and the stock airbox? Ski is stock other than pre-mix.


  2. #2

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    Never mind
    Last edited by 992door; 04-16-2013 at 12:10 PM.

  3. #3
    I guess I should clarify - the ski has the stock airbox, stock jets and stock screw settings for the 1.2 seat 95g but is being changed to the 1.5 seat and 115g.

    The GP1200 PDF manual http://www.guppa.se/downloads/Yamaha...760&GP1200.pdf indicates a 1.5 seat and has the screw positions. Are these for 55psi pop-off? Can anyone confirm these are valid?

  4. #4
    Yamaha artisan Cutlass's Avatar
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    The stock pop-off pressure for a GP1200 65U is around 65 to 70psi and I'm not if you can get it that high with a 1.5 NS.
    The service manual does indicate a 1.5 NS but that is incorrect. they came with 1.2 NS

  5. #5
    Happily Self-Employed WFO's Avatar
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    I have specs for stock and ported 65Us, and stock says 1.2s. 115/135 w/115g

  6. #6
    Yamaha artisan Cutlass's Avatar
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    The stock pilots are actually 100, 95, 97.5 (cyl 1,2,3) and all the mains are 135. But Oside had been recommending 100 pilots across the board and leaving the 135 mains for stock and mostly stock 65U.
    With aftermarket flame arrestors (stock or mostly stock engine), use 1.5 NS and 115g springs to achieve a 50 to 55psi pop-off.

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