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  1. #1

    gp1200 jetting help

    I've been fighting with this ski for the past year and can not get it running right. I just found one of the plug wires was broken inside so I fixed it and thought it would fix the ski but now my plugs are showing a lean condition.

    Anyone have an idea on where to start with jetting?

    Aftermarket head running 150ish psi
    Aftermarket FA's
    Aftermarket impeller
    Running premium

    It seemed to get better as I turned the high screws out on the carbs but I think i'm beyond their useable range now. The ski just doesn't seem to have all the top end it used to and when WOT you can hear the revs almost sound like they're hitting rev limiter but I know I'm not.

  2. #2

    Join Date
    Sep 2013
    Bennettsville, SC
    because of the aftermarket FA's, you may need to increase your high speed jet size. Remember, double and triple carb setups may have a larger high speed jet in #2 and #3 than in #1. Its to compensate for the torsional twist of the crankshaft changing the timing of the aft cylinder(s)

  3. #3
    Yamaha artisan Cutlass's Avatar
    Join Date
    Oct 2010
    Madison, WI, USA
    The setup that is tried and true for a stock or mostly stock GP1200 engines with a aftermarket flame arrestor is the following:
    Use the 115 gram spring with the 1.5 NS to get a pop off of around 50 to 55 psi. Run all 3 carbs with 100 pilots jets and the highs should all be the stock 135.
    Run the low speed screws all at 1 1/4 out and the highs at 1 1/2 out.
    Thats exactly how I run mine and it runs perfect.
    Your higher compression has little affect on jetting/carb set up but do some minor hi/low speed screw adjustment if you feel you need to.

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