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Manufacturing Replacement Jets

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    Manufacturing Replacement Jets

    it's still possible to buy replacement jets, but this thread will explore the idea of making our own. eventually i want to be able to make any replacement part for any petrol driven engine, so let's look at some engineering ideas here.

    talon kindly provided an image of a slow jet. here i'm using it as an example of trying to find the total surface area of jet bores in a jet, using high resolution photos. we may even be able to calculate the resolution required in order to accurately calculate the areas with necessary precision. of course, if there is a datasheet out there then we could use that instead..

    the photo needs to be calibrated first. we take 'A' as the measurement of the actual jet, using a micrometre, to the greatest precision available. then we measure 'B' of each bore in the photo. by using 'A' we can find the area of 'B' without measuring it directly, only from the photo.

    exercise : would anyone care to draw up a formula for that, i.e. B as a function of A ?

    next episode : how do we reproduce a jet using only commonly available tools ?

    ( any ideas, feedback or constructive criticism are welcome ! )


    20220902_204909.jpg



    Show proper respect to everyone, love the family of believers, fear God, honor the emperor.
    1 Peter 2:17

    #2
    a jet is about $2-$4

    Tobias YOu are a nut.
    Don't spend money and buy, spend time and learn.

    Comment


      #3
      haha yea. well maybe ... but even if you can get them that cheaply, its great to learn self sufficency

      mark my words, a day will come when any kind of carb or petrol engine will be either :

      - hard to find
      - impossible to find
      - very expensive

      do you feel like driving vehicles that dont have any voice or any soul ? rhetorical ...
      Show proper respect to everyone, love the family of believers, fear God, honor the emperor.
      1 Peter 2:17

      Comment


        #4
        OMG !!

        this guy is full of it (theory) with little practical knowledge or experience.

        most riders here can manage a simple carb cleaning without resorting to deluded and abstruse thinking to explain why it can't be done. and there is NO WAY he could make a useful idle jet from scratch, no matter how many measurements he might make.
        Last edited by squirrelman; 4 Weeks Ago.
        "It's only getting worse."


        MY rides: '97 VFR750, '90 Red Hawk, '88 Blue/Black Hawk, '86 RWB VFR700 (3), '86 Yamaha Radian, '90 VTR250, '89 VTR250 (2), '73 CB125, '66 Yamaha YL-1

        Sold: '86 FJ1200, '92 ZX-7, '90 Radian, '73 CB750, '89 all-white Hawk, '88 blue Hawk, '86 FZ600, '86 Yam Fazer 700 , '89 VTR250, '87 VFR700F2, '86 VFR700F.

        Comment


          #5
          ah brother, you just wana troll on me huh ?

          i did pure math degrees, so engineering is more entertainment than work haha

          cant be done ? of course if i want someone to clean carb only, its a nice boring and simple task for my little child. i hope he doesn't get bored quick too, poor little guy !

          anyway let's get to work. if anyone can find for me the typical vacuum levels of bros400, i'll show you guys the magic

          exercise 1 : draw up a formula for calculation of bore size from photo, i.e. B as a function of A ?

          exercise 2 : vacuum data for a bros400 engine as it's meant to run

          or just sit around with telescope and complain that the moonwalkers are doing a bad job
          Show proper respect to everyone, love the family of believers, fear God, honor the emperor.
          1 Peter 2:17

          Comment


            #6
            Does one have to be an astrophysist to recognize a limp?

            If you were looking for a support group you're barking up the wrong tree. This place is fulla enablers dude. - Shooter77us

            The bitterness of low quality lingers long after the thrill of a low price has gone. - RacerX450

            Comment


              #7
              Originally Posted by ParcNHawk View Post
              Does one have to be an astrophysist to recognize a limp?
              haha
              Show proper respect to everyone, love the family of believers, fear God, honor the emperor.
              1 Peter 2:17

              Comment


                #8
                slow jet measurements.png

                here's measurements from the two jets i have.. obv we can round up to guess what they are meant to measure as
                Show proper respect to everyone, love the family of believers, fear God, honor the emperor.
                1 Peter 2:17

                Comment


                  #9
                  current open questions for the team :

                  exercise 1 : draw up a formula for calculation of bore size from photo, i.e. B as a function of A ?

                  exercise 2 : vacuum data for a bros400 engine as it's meant to run

                  exercise 3 : why is there a standoff (slightly larger diameter of cylinder) at the end of the jet stem (slow jet) ?

                  exercise 4 : does the homemade jet need to have the same number of holes as the original ? what are the main parameters for good jet operation ?

                  exercise 5 : why are jets commonly constructed from brass and not steel ?
                  Last edited by Tobias Funke; 4 Weeks Ago.
                  Show proper respect to everyone, love the family of believers, fear God, honor the emperor.
                  1 Peter 2:17

                  Comment


                    #10
                    Originally Posted by Tobias Funke View Post
                    ah brother, you just wana troll on me huh ?


                    exercise 2 : vacuum data for a bros400 engine as it's meant to run
                    :
                    Intake vacuum or throttle plate vacuum?
                    You DO know the difference... right?

                    Comment


                      #11
                      Originally Posted by bitzz View Post

                      Intake vacuum or throttle plate vacuum?
                      everything thanks
                      Show proper respect to everyone, love the family of believers, fear God, honor the emperor.
                      1 Peter 2:17

                      Comment


                        #12
                        slow jet seating.png

                        here's how i think the idle jet is seated
                        Show proper respect to everyone, love the family of believers, fear God, honor the emperor.
                        1 Peter 2:17

                        Comment


                          #13
                          aluminium rod.png

                          if you can find 6mm OD with 2mm ID then it's going to save you some time on this. otherwise buy the 6mm bar as i am. note : we aren't going to copy the same original design, so it's ok for the inner channel to be larger.
                          Show proper respect to everyone, love the family of believers, fear God, honor the emperor.
                          1 Peter 2:17

                          Comment


                            #14
                            men watch this for inspiration !

                            https://www.youtube.com/watch?v=FBi3TKDdwT8

                            did we progress to a more ' enlightened age '

                            or perhaps humans are starting to drift from things they can understand and control ?

                            i'll always be fine buddies, no matter how complex and abstract things get

                            but our countrymen, i fear they are ill equipped for the future of my darkest suspicions

                            ( rant completed )
                            Show proper respect to everyone, love the family of believers, fear God, honor the emperor.
                            1 Peter 2:17

                            Comment


                              #15
                              Well, I have to say, you got me to read the thread!

                              I would suggest using brass, rather than aluminum. I suspect this is done on OE carbs to prevent corrosion fusing the parts.

                              That said, I gotta ask the obvious question of why?

                              A jet would be really easy to make, but they are cheap and plentiful. If you just want to build an engine, why not build a whole carb? Or for that matter, a whole engine? There are people who do this, and it’s really neat.

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