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Another Jetting Question

Discussion in 'CVP Stage 1 Tuners Kit' started by Merel Jones, Apr 18, 2016.

  1. Merel Jones

    Merel Jones Member

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    My first post. I have a 2002 Harley Dyna TC88 with a CV stock carburetor. The bike has an aftermarket high flow air cleaner, RB Racing 2 into 1 exhaust system, and recently installed S&S G510 cams. I purchase jets, emulsions tube, Velocity needle and EZ just screw from CV Performance after installing the cams. The jets are currently 46/185. The 185 main jet seems small for the bike set up but it is not lean at higher rpms. I am having the problem with the EZ just screw not impacting the idle at all. No apparent change no matter where it is set. I was sure to clean the passages and blow them out when changing the jets. In addition to this issue the fuel mileage has dropped off dramaticly, was 43-48 now 33-36 mpg. I did not get jet sizing information with the parts I bought so I am not sure if I have missed something. Do my jet sizes look correct? Would the CV Performance emulsion tube or needle have an impact on what jets I should be using? Any help would be appreciated. By the way I am 68 years old and do not hot rod the bike so that shouldn't be the cause for the drop in mpg.
    Thanks for any help
    Merel Jones, Apr 18, 2016
    #1
  3. kenfuzed

    kenfuzed Administrator Staff Member

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    Hi Merel, it can be common on Twin Cams to not be able to find the bottom stumble with the EZ-Just since the ignition system on that model can compensate and mask that low idle stumble. It is often better to adjust by starting around 1-1/2 turns out and a very low idle, then blipping the throttle which should produce a slight hesitation or cough. Adjust the screw out another 1/8th and repeat until you no longer have any cough when cracking open the throttle. After adjusting readjust the idle back to it's normal range. That will be your sweet spot.

    When replacing the emulsion tube make sure the needle jet (stainless steel nozzle) is oriented correctly. An upside down needle jet (or missing) can lead to mileage issues. See #3 under our trouble shooting page for how this should look.
    https://cv-performance.com/harley-cv-carburetor-tuning-issues

    Jetting seems a bit lean on the main side and you could go up to a 190, but if mileage is already a concern and you are not running lean up top then stick with your 185. Just make sure the 185 you are using is either a Harley brand jet or one of ours, since other brands may have variations that make comparisons impossible.

    When installing our needle check that you did not include any shims or washers from a prior installation. That would make the midrange very rich and could also contribute to the lower mileage.

    Other things to consider include making sure the slide has not been drilled, spring cut, or any other passage clogged when the others were cleaned out.
    kenfuzed, Apr 18, 2016
    #2

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