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Thread: jet question

  1. #1
    jweiss Guest

    Default jet question

    I have an 06 stock nighttrain and installed the short mean mothers.
    When slowing down i get popping thru the carb and the plugs indicate it is running lean.

    Which jets should i switch to and what setting if needed should be done to the needle ?
    It is not injected.

  2. #2
    Join Date
    Aug 2008
    Location
    Blackfoot, ID
    Posts
    120

    Default Shim the jet needle up slightly

    If you're unwilling to remove several diffuser discs, then you can use this long known tuning trick.

    For the washers I use fiber washers from Home Depot's specialty drawers. They are labeled as follows:

    Fiber Washer
    032" Thick
    #4-ID x 1/4" OD (3/32-ID x 1/4" OD)
    4 pcs
    $0.59

    I would recommend mic'ing them, b/c there are subtle variations in their thicknesses ~030" - 032."

    Since they're so cheap, buy a couple of sets. That way you'll be certain to match two identical height washers, one or two to each jet needle depending on how much richer you want to go. Beware that the richer you go the poorer your MPG.

    Place the fiber washer between your existing jet needle washer and the top of the jet needle. Then synchronize your carbs for a dreamy ride.


  3. #3
    jweiss Guest

    Default

    thanks kz550,
    The photo is very helpful.
    My pipes do not have deffuser discs... by going by the pictures from the web site, i am gussing that they are the mean mothers (short), but they look a lot like the vance hines short shots. they are deffinitly marked super traps.

    I have only one carb, so there will not be a need to synchronize the "carbs".
    I have heard of the washers under the needle, but was looking more for info on what jets to use. ( pilot jet and main jet )
    I should mention its a 2006 harley night train, 88 ci with a screamming eagale air filter.

    Looking forward to any help please.

  4. #4
    Join Date
    Aug 2008
    Location
    Blackfoot, ID
    Posts
    120

    Default

    The shim concept would still apply even if you decided to bump your main jet. You're running an open SuperTrapp, so multiply the main jet by something between 1.03 to 1.05. Along with the jet needle shim, your popping should be reduced, if not eliminated. And your power should be noticeably better, unless you're elevation is above 2,500.'

    You know, SuperTrapp has an open end-cap design too. That way you can find a better compromise for top and mid-range power, without sacrificing too much of the loud exhaust note you've got now. It'll give you more tuning possibilities.

  5. #5
    bschultz Guest

    Default

    If you decide to go the jetting route ... try a 78 main and a 31 intermediate.

  6. #6
    jweiss Guest

    Default

    Thanx guys... once i get jets and have a chance to change them, i will let you know the outcome.

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