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  1. #1
    spud's Avatar
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    Blocking Manifold Passages

    Is it worth it to plug the passages between the carbs on the intake manifold?


  2. #2
    philip_gpr's Avatar
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    yes

    you can read about it on groupK

  3. #3
    spud's Avatar
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    Cool. The racks are off both skis. I'll get right after it tonight.

  4. #4
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    yes Jim, It will give the carbs a better signal at higher rpm's.

  5. #5
    Canadian POWERHOUSE CanadianGPR's Avatar
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    It is kinda hard to find on their site.

    From the Group k website - Many 2-cycle pwc engines (Yamaha 1200s included) employ the use of intake manifold cross-over channels to improve the smoothness of low speed carburetion. These cross-overs work very effectively for stock engine platforms. However on a setup built for high rpm output, these cross-overs can significantly reduce inlet signal at high rpm. This reduction in high rpm signal is not a problem for stock engines, however it can cause uneven “full throttle” fuel metering on a high rpm modified platform. In testing we’ve done on other modified pwcs, we have found that simply blocking off these inlet manifold cross-over channels can yield a big improvement in the accuracy of fuel metering during extended full throttle passes.

  6. #6
    Canadian POWERHOUSE CanadianGPR's Avatar
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    What is best to block the the passages off with? My carbs are off too

  7. #7
    Moderator OsideBill's Avatar
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    I used JB Weld it was recomended to me to do this by Art at Jetworks he had me block off the crossover on my intake between the Mag and PTO carbs as well as the crossover channels between the reed valves on my GP1200 intake manifold. Worked out great put it on let set awhile until firm and before it completely hardens shave it with a razor knife blade job complete. mine was on flat surfaces I do not know how they are on the GPR Good luck

  8. #8
    Moderator RX951's Avatar
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    yUp. did mine with JB-Weld






  9. #9
    spud's Avatar
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    I have heard this and read it before, but it sounds good to hear it from people that have real world experience.

  10. #10
    spud's Avatar
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    JB weld is in. I put an inline restrictor in too. I used a 100 main jet. Does that sound about right. I have heard 95 or 100. Just a little sanity check.

    I've just about got the 1200 wrapped up. The parts will be rolling in from Lowell before long and a package ported 1300 will breathe life. Can't wait.

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