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  1. #1

    Join Date
    Aug 2006
    Orange County, Ca

    Filling Cross Port on carb Manifold

    On the GP1200R Manifold, Is there any advantage on fill in the cross port ???

  2. #2
    XL1200Ltd-Keith's Avatar
    Join Date
    Aug 2005
    This is a quote from a Group K technical article.

    Inlet Signal Part 2 - Many 2-cycle pwc engines (Yamaha 1200s included) employ the use of intake manifold cross-over channels to improve the smooth-ness 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.

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