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To drill or not to drill: that 7/64 option?

Discussion in 'CVP Stage 1 Tuners Kit' started by HopperXL, Sep 11, 2014.

  1. HopperXL

    HopperXL Member

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    Hi All
    The instructions on the tuner kit say that drilling out the slide hole to 7/64 is "optional".

    What are the options? What is the advantage of drilling it to 7/64? What is the advantage of leaving the hole stock size?

    The hole in the slide I have is at least .005" smaller than the drill size, somewhere round .098" I think. The slide comes from a donor carb of unknown origin because PO had drilled the original slide's hole to .137.

    Bike is a stock 95 Road King with mild slip on pipes and KN air filter. Used for two up touring mostly.

    So should I drill to 7/64, or not drill? And why?

    Thanks
    Hopper
  2. kenfuzed

    kenfuzed Administrator Staff Member

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    Hi Hopper, the drilling is optional because not everyone needs to do this. Generally lighter bikes (Sportsters, Dynas) do better with a drilled slide, whereas cruisers or those ridden 2-up fair better without drilling. The difference is extremely slight between a slide left undrilled or drilled out to 7/64. I have this as "optional" because there are those who favor drilling and it won't typically have any negative impact to drill with this smaller bit. The origins behind drilling with a 7/64 bit was to clean up older slides that had burs from the factory. This is not the case with newer slides.

    It should be emphasized that drilling a slide with a larger bit (1/8th or more) will cause irreversible damage to the slide that will lead to tuning problems and issues with the slide wandering or bouncing as it searches for the correct position.

    My best advice based on your 2-up riding style, leave the slide undrilled.
  3. HopperXL

    HopperXL Member

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    Thanks Ken. That has clarified it perfectly. I will leave the drill well alone.



    Thanks for your help.
    Last edited: Sep 12, 2014
  4. HopperXL

    HopperXL Member

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    Very nice result indeed. Got it back together with a stock undrilled slide (.093"), set the idle mix screw to 2-1/8 turns open as recommended and away she went, beautiful. Midrange flat spot ironed right out.

    Tried leaning out the idle mix and then bringing it back 1/8 turn etc but got carb farts so after a day of riding and fiddling, ended up back at the original 2-1/8 setting! Sweet as.

    Thanks again
    Hopper

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