Pilot jet hole differences
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Thread: Pilot jet hole differences

  1. #1
    Senior Member BUMBLESPECIMOODA's Avatar
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    Pilot jet hole differences

    I've noticed that the holes "A", are likely what changes for the different pilot-jet sizes.

    I've also noticed that the holes "B", are different between pilot-jet manufacturers.

    My questions are:

    1. Does the "B" holes matter in the way that the jet performs?

    2. Will the different "B" hole sizes between manufacturers complicate consistency when tuning?

    3. Should I drill out the "B" holes on all my different pilot-jets to add consistancy, if question #2 matters?

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    Last edited by BUMBLESPECIMOODA; 10-17-2019 at 12:00 PM.
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  2. #2
    Senior Member elime's Avatar
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    If you have the early carb you can go to Aliexpress and buy a dozen jets of assorted sizes, both pilot and high speed. I don't know if these will work in the newer carbs. Shipping takes a while but well worth the wait.

    3645d.jpg3645h.jpgP4080027b.jpgPilot jets.jpg

    https://www.aliexpress.com/item/3226...56234c4dh5rnT3

    High speed jets: https://www.aliexpress.com/item/3226...27424c4dJg66F4
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    Long live the internal combustion engine!

  3. #3
    Senior Member MtnMan75's Avatar
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    Between different brands the numbers begin to mean nothing. For instance... recently I bought some Teikei and Procycle jets. While the diameters look to be the same looking through them, the length of the jet's channel ("A" in your drawings) is almost three times longer on Procycle jets which meant I needed to use their 135 for similar flow to a Teikei 126, whereas a Teikei 135 would have my cylinder swimming with gas upon opening the throttle. Unless you get really lucky when tuning, by the time you nail it you could probably get to the jet and needle blindfolded. Even the new TK 32.5 pilot jet compared to the original one that is in this carb has a flat face where the screwdriver goes in and somehow that results in less flow than the original 31 which has the rounded look in elime's previous post. I also think the fact that some brands of main jets sit farther down into the float bowl when fully seated is a huge factor as well.

    Even one brand's pilot screw which may look identical to the naked eye may end up having a much different flow rate than another to the point you'd end up needing to change the pilot jet to match. (I've run into this a few times and held them up to a light one in front of the other and swore they looked exactly the same, but upon laying the needle portions against each other found the taper was different ever so slightly which results in more than a couple turns to have the same flow)
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  5. #4
    Senior Member BUMBLESPECIMOODA's Avatar
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    Thanks gang.

    I'm gonna get an assortment of micro drill bits for what I have, and gonna get the jet assortmet kit.

  6. #5
    Senior Member elime's Avatar
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    Quote Originally Posted by BUMBLESPECIMOODA View Post
    Thanks gang.

    I'm gonna get an assortment of micro drill bits for what I have, and gonna get the jet assortmet kit.
    You can spend all day getting everything dialed in perfectly and have the sweetest running bike of all time then a day goes by, the temperature changes, along with the humidity and the barometric pressure and its not a perfectly running machine anymore. Doesn't matter. Have fun. Good luck. Report back how it goes.
    Long live the internal combustion engine!

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