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Thread: Mixture Screws

  1. #1

    Mixture Screws

    Does turning the the high and low speed screws OUT richen the mixture?? My ski was running good after last years rebuild. I looked at the wash today and the Mag and Pto pistons looked a little lean.

    I turned both high screws out about 1/8 turn and all 3 Low speed screws out about 1/8 turn as well. Now the ski is a monster it runs 52mph at wot. I've heard horror stories of a lean ski running awesome just before toasting a piston.

    I hope I richened the mixture by turning the screws OUT.

  2. #2
    johnsonmtz's Avatar
    Join Date
    Oct 2006
    Mt. Zion Illinois
    Yes, turning the screws out allows more fuel to flow on each of the circuits. If you gained speed (and RPM) by making the mixture richer, then that means you were running lean before.

    Did you set the needles to factory specs after your rebuild? Usually these are pretty safe settings and tend to be a little rich.

    There are others more knowledgeable on tuning, but I'd suggest you set them to factory specs and head to the lake. Make a short WOT run and record (remember) the max RPM you achieved. Now, turn each high needle out 1/8 turn and repeat the same run. Did RPM increase? If so, the extra fuel helped. Keep doing this until the 1/8 turn reduces your RPM, this means you've reached an over-rich point. Go back to the last setting that gave you the highest RPM.

    This should be a good setting for your. Make some runs and check piston wash to verify these needle settings are good.

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    That's good advice ^^^^^^^^

    Yes, out is richer.

  4. #4
    Yes all 3 carbs where set to factory specs. I did a complete engine rebuild at the end of last season. This it the 3rd time I've had it out since break in. This was my first look at the pistons. I will keep making the adjustments you suggested

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