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  1. #1
    PolarisNut's Avatar
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    Pop off on big carbs and Domestic tripples

    Al-What are you running for needle/seat and springs in your Matrix II with the Novi carbs? Crazy, what about you? I'm trying to figure out what to do about fuel shaking from the boosters at 2000-4000 rpm. I've got 2.0 needle/seat and 115g springs, which should be good for about 32psi. Trying to figure out if I just need new needles (a few years old), or if I need to raise the pop off more. I know the Yami guys run 1.5 seats and popoff in the 50ish range to stop this from happening on the bigger tripples. Any of you guys doubling up on your check valves? Ski runs great, except for this issue.


  2. #2
    cheatin' piston popper addicted's Avatar
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    Can't speak for triple pipes, but I have a 1100 and 1200 yammi's. Both have double check valves in the kidneys and 1.5 n&s. Popoff on 1 is low 40's, the other is mid 50's. both run oem mikuni 44's. The shaking is probably making the needles unseat. I read somewhere that a 1.5n&s flows as much gas as the oem pumps can provide. anything larger is just for setting the popoff. probably groupK's site.

    Try a 1.5 needle with a lighter spring to get close to the same popoff and try it.

  3. #3
    PolarisNut's Avatar
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    Quote Originally Posted by addicted View Post
    I read somewhere that a 1.5n&s flows as much gas as the oem pumps can provide. anything larger is just for setting the popoff. probably groupK's site.

    Try a 1.5 needle with a lighter spring to get close to the same popoff and try it.
    Thanks...yeah, I've seen that before. Some feel that that isn't the case though I know Randy likes to use 2.3 or 2.5s.

  4. #4
    cheatin' piston popper addicted's Avatar
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    don't know

    But, if it's dripping and the n&s are ok, you really have no choice but to go with a 1.5 since youre maxed out on the spring.

    If you don't mind pulling the carbs, add a check valve and see what happens with the current popoff.

  5. #5
    Are you seeing this on the front and back carbs. mostly? Are you seeing this when running the engine on the trailer in the water or out of the water. Running the engine on a trailer out of the water unloaded seems to increase vibration from my experience. Yes doubling the check valves will help but will also lean out the fuel delivery in the transition to the high speed circuitry.

  6. #6
    PolarisNut's Avatar
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    Quote Originally Posted by laskt View Post
    Are you seeing this on the front and back carbs. mostly? Are you seeing this when running the engine on the trailer in the water or out of the water. Running the engine on a trailer out of the water unloaded seems to increase vibration from my experience. Yes doubling the check valves will help but will also lean out the fuel delivery in the transition to the high speed circuitry.
    Yes, PTO and CEN carbs mainly. It is real bad on the trailer, but still does it in the water.

  7. #7
    Surprised that the mag and pto carbs aren't the worst because the center carb. shouldn't vibrate as much from the engine rocking back and forth. Should verify pop-off pressure and fuel return pressure to start with.

  8. #8
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    ???

    Didn't See Where You Mentioned Fuel Pressure At Idle???what Is It???1-2 Psi At Idle Is What Your Looking For And 5-6 At Wot

  9. #9
    PolarisNut's Avatar
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    Quote Originally Posted by TxPro1200 View Post
    Didn't See Where You Mentioned Fuel Pressure At Idle???what Is It???1-2 Psi At Idle Is What Your Looking For And 5-6 At Wot
    Haven't checked it yet, but it still does it with no return restrictor.

  10. #10
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    CARBS

    RUBBER SPIGOT MOUNTS?????THE 47'S DID THE SAME THING ON THE PRO.THATS WHY I LIKED GOING THE 42 ROUTE SO MUCH WITH THE STOCK PORTING,I SEEM TO REMEBER TRYING TO TALK YOU INTO 44 PRO CARBS EVEN DOUBLING THE CHECK VALVES DIDN'T STOP ALL OF IT

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