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Jets

Discussion in 'XJ Modifications' started by noob, May 31, 2008.

  1. noob

    noob Member

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    I'm starting the fun and very pleasant job of re-jetting my XJ750 for pod filters and a straigh through exhaust.

    By any chance do the Mikuni and Hitachi carbs use the same main jets? I can get Mikuni jets easilly, but Hitachi ones seem to be a bugger to find, and I have Hitachi carbs.
     
  2. tumbleweed_biff

    tumbleweed_biff Active Member

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  3. samsr

    samsr Member

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    They are not the same.
     
  4. prime

    prime Member

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    I just bought some jets for my Hitachi from Chacal on here. Hit him up, he'll take care of you. He has a big post in the sell/trade forum.
     
  5. noob

    noob Member

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    I've had to resort to getting a 1.25mm drill bit on order and I'll have to drill the holes out tomorrow. if that fails then it's order them from new zealand and wait a few weeks to get em.
     
  6. martinfan30

    martinfan30 Member

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    I'm curious, what is your new jetting settings? I just ordered some as well,I was running dangerously lean at cruise speeds.
     
  7. baz666

    baz666 Member

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    There's a company here in Canada, near Toronto, that sells Hitachi mains, pilots and needles. I was looking at their catalog about an hour ago at my local bike shop while I was searching for Mikuni jets for my XJ900.
    His email address is:
    tech@mcdistributing.com

    good luck,
    baz
     
  8. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Always in stock, fast shipping worldwide:

    Main & Pilot Fuel Jets:


    ee) Aftermarket Hitachi brass MAIN FUEL JETS, sizes as follows, fits all XJ650 (except Turbo), all XJ750, and all XJ700 (exc. "X") models.

    NOTE: stock Hitachi XJ series carbs used the following original sizes:

    #106 (XJ 750RL Seca, 1984 only)
    #107 (XJ700 non-X)
    #110 (XJ650 models)
    #120 (all XJ750 models except 1984 XJ750RL Seca)

    All the other sizes are for "tuning" or re-jetting purposes when changing intakes or exhaust systems.


    HCP6316 Aftermarket brass #106 MAIN FUEL JET, stock size for '84 XJ750RL Seca models, each:
    $ 6.00

    HCP6316SET4 Aftermarket brass #106 MAIN FUEL JET, set of 4:
    $ 21.95


    HCP6317 Aftermarket brass #107 MAIN FUEL JET, stock size for XJ700 non-X models, each:
    $ 6.00

    HCP6317SET4 Aftermarket brass #107 MAIN FUEL JET, set of 4:
    $ 21.95


    HCP6318 Aftermarket brass #108 MAIN FUEL JET, each:
    $ 6.00

    HCP6318SET4 Aftermarket brass #108 MAIN FUEL JET, set of 4:
    $ 21.95


    HCP6319 Aftermarket brass #109 MAIN FUEL JET, each:
    $ 6.00

    HCP6319SET4 Aftermarket brass #109 MAIN FUEL JET, set of 4:
    $ 21.95


    HCP873 aftermarket brass #110 MAIN FUEL JET, stock size for most XJ650 models, each:
    $ 3.25

    HCP873SET4 Aftermarket brass #110 MAIN FUEL JET, set of 4:
    $ 11.95


    HCP874 aftermarket brass #112 MAIN FUEL JET, each:
    $ 3.25

    HCP874SET4 Aftermarket brass #112 MAIN FUEL JET, set of 4:
    $ 11.95


    HCP875 aftermarket brass #116 MAIN FUEL JET, each:
    $ 3.25

    HCP875SET4 Aftermarket brass #116 MAIN FUEL JET, set of 4:
    $ 11.95


    HCP876 aftermarket brass #118 MAIN FUEL JET, each:
    $ 3.25

    HCP876SET4 Aftermarket brass #118 MAIN FUEL JET, set of 4:
    $ 11.95


    HCP877 aftermarket brass #120 MAIN FUEL JET, stock size for most XJ750 models, each:
    $ 6.00

    HCP877SET4 Aftermarket brass #120 MAIN FUEL JET, set of 4:
    $ 21.95


    HCP878 aftermarket brass #122 MAIN FUEL JET, each:
    $ 3.25

    HCP878SET4 Aftermarket brass #122 MAIN FUEL JET, set of 4:
    $ 11.95


    HCP879 aftermarket brass #124 MAIN FUEL JET, each:
    $ 3.25

    HCP879SET4 Aftermarket brass #124 MAIN FUEL JET, set of 4:
    $ 11.95


    HCP880 aftermarket brass #126 MAIN FUEL JET, each:
    $ 3.25

    HCP880SET4 Aftermarket brass #126 MAIN FUEL JET, set of 4:
    $ 11.95


    HCP881 aftermarket brass #128 MAIN FUEL JET, each:
    $ 3.25

    HCP881SET4 Aftermarket brass #128 MAIN FUEL JET, set of 4:
    $ 11.95


    HCP882 aftermarket brass #130 MAIN FUEL JET, each:
    $ 3.25

    HCP882SET4 Aftermarket brass #130 MAIN FUEL JET, set of 4:
    $ 11.95


    HCP883 aftermarket brass #132 MAIN FUEL JET, each:
    $ 3.25

    HCP883SET4 Aftermarket brass #132 MAIN FUEL JET, set of 4:
    $ 11.95


    HCP884 aftermarket brass #134 MAIN FUEL JET, each:
    $ 3.25

    HCP884SET4 Aftermarket brass #134 MAIN FUEL JET, set of 4:
    $ 11.95



    xx3) Reproduction Hitachi main fuel jet SPACER WASHER, round flat copper washer goes under the head of the main fuel jet. Perfectly replaces missing or bowed originals.

    HCP887 Hitachi carbs main fuel jet spacer washer, each:
    $ 4.50

    HCP887SET4 Hitachi carbs main fuel jet spacer washer, set of 4:
    $ 15.00



    ff) Aftermarket Hitachi PILOT FUEL JET, sizes as follows, fits all XJ650 (except Turbo), all XJ750, and all XJ700 (exc. "X") models.

    NOTE: stock Hitachi XJ series carbs used the following original sizes:

    #36.5 all XJ700 non-X models.
    #40 all XJ650 models, all XJ750 (USA) models, and XJ750RL (1984).
    #43: some Canadian-Euro-UK XJ750 models.


    The #41, #42, sizes can also be used for "tuning" or re-jetting purposes when changing intakes or exhaust systems.


    HCP885 aftermarket brass #40 PILOT FUEL JET, each:
    $ 3.25

    HCP885SET4 aftermarket brass #40 PILOT FUEL JETS, set of 4:
    $ 11.95


    HCP886 aftermarket brass #41 PILOT FUEL JET, each:
    $ 3.25

    HCP886SET4 aftermarket brass #41 PILOT FUEL JETS, set of 4:
    $ 11.95


    HCP6326 aftermarket brass #42 PILOT FUEL JET, each:
    $ 5.50

    HCP6326SET4 aftermarket brass #42 PILOT FUEL JET, set of 4:
    $ 19.95


    HCP6320 aftermarket brass #43 PILOT FUEL JET, each:
    $ 5.50

    HCP6320SET4 aftermarket brass #43 PILOT FUEL JET, set of 4:
    $ 19.95





    WHAT ABOUT RE-JETTING FOR PODS, ETC?:

    It's a question we get asked often and unfortunately, one that we cannot answer honestly about your specific bike besides with "it depends".

    Which is a nice way of saying "you're about to enter the seventh circle of hell......."!

    Carb jet tuning required by aftermarket modifications is somewhat of a black art, part science, part skill, part luck. It depends on the current state of tube of your engine, your altitude, the mix of aftermarket parts on your bike, etc........alot of variables.

    The best advice we can offer is: Just Say No. Don't do it! Leave eberything stock!

    But, since most people---with good reason, I might add---don't always listen to our well-intentioned advice, then the next best recommendation we can offer is: "if you want more power get a bigger bike!".

    And that doesn't cut it with many riders, either, so for the remaining stalwarts out there who insist on "experimenting" with aftermarket intake and exhaust systems, here's the best information that we've come across to give you some GUIDANCE, which you should take as just that, and not as ANSWERS, because it isn't!

    We wish you luck with your endeavors!

    ******************************************************

    Hi xyz!.....we've never used pods on any of our bikes, they just seem like way too much trouble to me! BUT, here is the "standard" re-jetting recommendations from people who fool around with them....although, please be aware that every situation is different, and you should expect to go through some amount of trial and error (and frustration!) before you get it as close to right as is possible.

    By the way, the most important part of the information below is in the section titled "PRECAUTIONS"!:

    So here is the info regarding jetting that you might find helpful:


    MAIN FUEL JET SIZE CHANGES NEEDED PER TYPICAL MODIFICATION:


    Exhaust Changes:

    +2 main fuel jet size for custom 4-into-2 exhaust

    +4 main fuel jet sizes for 4-into-1 exhaust

    +4 main jet sizes for no muffler (open headers)


    Intake Changes:

    +2 main fuel jet sizes for single K&N filter (inside a stock airbox)

    +2 main fuel jet size for drilling holes in the airbox

    +4 main fuel jet sizes for individual pod filters (no airbox)


    Additional changes:

    - Add up all the main fuel jet size increases and subtract 2 sizes.

    - Decrease main fuel jet size by 2 per every 2000' above sea level.

    - Under a mis-match condition, such as when using pod filters with a 100% stock exhaust, or 4-into-1 header with stock filter and air box, then subtract 2 main fuel jet sizes.


    PILOT FUEL JET SIZES CHANGES NEEDED PER TYPICAL MODIFICATION:

    Pilot fuel jet size changes are related only to the change in main fuel jet sizes according to the main fuel jet size formula described above. Note that this pilot fuel jet rule is for the main fuel jet size change BEFORE any main fuel jet altitude compensation is factored in:

    Increase the pilot fuel jet size +1 for every +3 main fuel jet size increases.

    Additional changes:

    - Decrease pilot fuel jet size by 1 for every 6000' above sea level.



    PRECAUTIONS:

    - Make sure your carbs are in perfect working order before making jet changes....meaning fully cleaned internally and rebuilt.

    - Check plug color often and adjust as needed, 2 main fuel jet sizes at a time and 1 pilot fuel jet size at a time. Bright white plug insulators are a sign of an overly lean fuel mixture condition and WILL cause damage to your engine over time, up to and including engine seizure!

    - Synch the carbs after each jet change.

    - Make sure the floats are set correctly

    - Seriously consider purchasing a Colortune Plug Tuning kit.

    - You may find it necessary to make changes to the size or shimming of the main jet needle. There are no guidelines on what or how to do these changes, this is true trial-and-error tuning!




    EXAMPLE:

    Stock Carb Settings:
    #120 Main Fuel Jet
    #40 Pilot Fuel Jet
    Y-13 Needle

    MAIN FUEL JET SIZE CALCULATIONS:

    Changes made:

    Exhaust:
    4 into 1 with Supertrapp = +4 Sizes Main Fuel Jet

    Intake:
    K&N Pod Filters = +4 sizes Main Fuel Jet
    ----------------------------
    Equals: +8 main fuel jet sizes baseline
    Subtract: -2 main fuel jet size per formula above
    ----------------------------
    Equals: +6 main fuel jet sizes due to modifications, thus:

    Stock main fuel jet size is: #120
    + 6 additional sizes
    = a #126 main fuel jet size
    ---------------------------
    Subtract: -2 main fuel jet sizes for Altitude of 2500' Average

    = #126 calculated from above
    -2 jet sizes for altitude adjustment

    = a #124 main fuel jet size.


    PILOT FUEL JET SIZE CALCULATIONS:

    The formula is: +1 pilot jet size increase for every +3 main jet sizes increased.

    Stock pilot fuel jet size is: #40
    + 2 additional jet sizes (since we went up +6 main fuel jet sizes before the altitude compensation was factored in)

    = a #42 pilot fuel jet size.

    Note that no altitude compensation is needed on the pilot fuel jet since our elevation is less than 6000' asl.


    ------------------------------

    RESULT:

    A #124 Main and #42 Pilot is A GOOD STARTING POINT.

    ******************************************************


    For further insights and understanding, the Holy Grail for performance carb tuning information can be found here:

    www.factorypro.com
     

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