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  1. #1

    Matrix...Got it!

    Well, it took 7yrs but it finally came together. From extended idle periods to any where in the throttle range, I'm able to pin it without hesitation/stumbling. It has a rough running 2500 to 3500 range if the throttle is held steady in that area, that will never go away. Not an area where the throttle is typically held steady, but if I choose too run a steady throttle within this range, I can pin the throttle without hesitation/stumbling. It will always have a 4500 to 5500 power surge, which is like a nitrous button, and can make it challenging to ride in rough water if the throttle is trying to be held steady just above or below this area. At this point I feel it is a 74mph bike on any given day, and a +74mph boat under ideal conditions. The "+" is currently 75mph. Its funny, now I'm at a point where a degree change in timing, a one size change in low speed jetting, or an ⅛ turn of the low speed screw is very noticeable.


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Xlint job!!!!!

    Now record your settings for later reference

  3. #3
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    Which carbs are you running,I really didn't get much talk time in messing with the exhaust pipe on mine.

  4. #4
    Novi 48mm. The other bike has 46mm blackjacks. The Novi seem to be easier to tune.

  5. #5
    johnsonmtz's Avatar
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    Quote Originally Posted by Just-Pinch-It View Post
    .....It has a rough running 2500 to 3500 range if the throttle is held steady in that area, that will never go away......It will always have a 4500 to 5500 power surge, which is like a nitrous button....
    That's just the nature of tuned, 2-stroke exhaust pipes. They have an optimal operating range and there just isn't getting around it.

    Great job getting that thing set up to give max performance in a wide range of throttle positions.

    KJ

  6. #6
    800AMSOIL4U's Avatar
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    I think you are talking about the vibration at the 2500 to 3500 range ? If so that is how that crank feels. It is not a full circle crank.

  7. #7
    PolarisNut's Avatar
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    Quote Originally Posted by 800AMSOIL4U View Post
    I think you are talking about the vibration at the 2500 to 3500 range ? If so that is how that crank feels. It is not a full circle crank.
    I thought the MSX cranks were the full circle design, like the 1050s? I could be remembering wrong. Either way, I'm sure that vibration is causing the needle/seat to leak a bit, and allowing the boosters to dribble. I couldn't ever get my 48mm Full Spectrums to stop dripping, on any of the 1200 Polaris triples they were on. That is what was causing the rough running in that RPM range. Tried double anti siphon valves and higher pop off...it got better, but still not perfect.

    My GPR does it a little as well, even though the motor runs a bit smoother. I just stay out of that RPM range.

    Glad to hear you have it running well. My buddy and I were commenting at the "gathering", how mean those boats sounded

  8. #8
    800AMSOIL4U's Avatar
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    They are just regular 1200 cranks.

  9. #9
    Good job on getting it dialed in! Sounds like a lot of people running triple pipes and mikuni carbs. have trouble dialing them in when dealing with the bad harmonics in the 2500-3500 rpm range. I have been dealing with the same problem with my triple piped pro 1200. I first ran 44 novis shaft to shaft with 3 check valves and about 27 psi pop-off. Rear carb. would always dribble in the 2000-4000 rpm range. Rotated the carbs. 180 degrees which helped some but didn't solve the problem. Bought some 48 mm novis and ran them in a parallel shaft configuration. Rear carb. quit dribbling, but the mag carb. now dribbles. Getting a full circle crank built right now so hopefully I will get it on the water this year to see the results.

  10. #10
    Felt that it was an issue with the carb regulator portion transitioning to the carburetion portion. Probably related more to crank harmonics. My friends bike with the blackjacks runs a "normal" psi for pop-off, and I have to run off the chart psi's and both
    have the ruff 2500 to 3500 range. I would think if we had dribbling issues, as we stayed in that range, the motor would load up. I was able to smooth out the 2000-2500 and 3500 to 4000 ranges with timing. They're are definite upper limits to timing to stay under in the idle to ⅓ throttle range that affect smoothness and good responsiveness. Is the 2500 to 3500 vibration something that can be fixed by timing? There might be some pipe temp involvement too. Have a few timing ideas to try, and will see where that goes.

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