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    Kohler Main Jet Question

    GOT ONE GOT ONE (possible problem, definite question)

    I bought a "lot" (about 8-10) of new main jets for Kohler/Carter carbs from EPay. They look identical to the originals (haven't measured ID or anything as of yet, just an eyeball assessment so far) because I had a few in a row carb jobs, where they fought me coming out, and at best, there is no more screwdriver slot left to be able to reinstall them.
    At worst, well, lets not go there. These are for #26 carbs.
    They are "blanks", as in no cross drilled holes. how critical is diameter of the cross drilled holes, (within reason) and hole placement?

    I remember being able to go down the street and get OE Kohler ones reasonably and readily. (this, in my high school days of the mid 1980s) No more it seems. so I ran across these and snagged them up. Right now I could use about 3 of them done up. I have those carbs still in pieces, all clean, each in their own separated boxes til I can get around to them.
    I do still have the best (least torn up) jet that needs replaced, that can be used as a rough guide.

    The reason I ask;
    I do remember (can we say Tecumseh here?) that with the carbs off the cast iron Tecumseh,s they had a "service jet" and said not to remove an OE one unless you had a service jet to go back in, which had a groove cut into the threaded "head" of the jet so that it could get air no matter how deep they happened to be threaded into the body. Originally they were drilled after install in the carb body, and no guarantee that after removing an original jet, that it would get screwed back in exactly the same amount as the spot it was screwed into originally, meaning the cross holes would not line up, and the engine would not run right at that point. from my days of playing with Sears/ Roper tractors...…… comparing what I remember from those days with what I am playing with ("mostly" anyways,) now, and honestly not 100% sure that what I remember from then and on those engines, applies here. I don't think it does.

    If this isn't feasible in the field at least I don't have much money tied up in them...…
    Don
    Kankakee IL

    #2
    Before I answer, I want to make sure we are talking about the same part. Are you referring to the main needle that goes in from the top? The long tip one with holes in the side? Or are you talking about the emulsion tube that screws in up from the bottom in the same hole the bowl bolt goes in?

    Both those parts have cross drilled holes. But they serve different purposes.
    ~Jonathan
    Oblong, Illinois

    Just because it's old, doesn't mean it's obsolete!

    I've got a lot of Cubs in the barn....but I have more implements/attachments!

    Comment


      #3
      the one that screws in from the bottom.... IDK if its the right terminology, but the thing that comes in from the top, has always been a "high speed mixture screw" to me.
      or "main mixture needle"
      Don
      Kankakee IL

      Comment


        #4
        Well Don...... I wish I could directly answer your question, but I just can't. This is the second time I have been stumped by a question like this. The last time it was I who asked the question! I never did find a good answer to my question either, but Don Vogt and I hammered it out enough that I was satisfied, and I moved on. (I won't get into my question, but it was similar to yours.)

        So, the simple answer is the holes in the body of the main jet are air bleed holes. They control how well fuel is delivered to the main fuel circuit during different pressures. (Throttle angles.) They have to be there, or the engine won't run correctly, but as far as how many holes, and how large, I strongly suggest as close to original as possible. As far as placement, the holes aren't "clocked". So you can place them anywhere in the circumference of the body, but height is important. I don't know how important, but I'm pretty confident that you don't need to use precise measuring tools to locate them down to the .001", but they need to be close.

        I prefer not to link to external sources, but in the interest of time, and the fact that the write up is so well written I don't want to compete, here is a link to a very good explanation of how a carb works. You can skip to the part where it explains the air bleed hole for the main jet.

        On another note, Zach Kerber sells new brass main jets, minus the air bleed holes. So, if you run out, or screw one up, you can grab a couple from him.

        That was a really, really good question. Sorry I can't directly answer it, but I hope I helped at least some!
        ~Jonathan
        Oblong, Illinois

        Just because it's old, doesn't mean it's obsolete!

        I've got a lot of Cubs in the barn....but I have more implements/attachments!

        Comment


          #5
          Yeah the ones that I have look just like the ones that zach sells. I haven't gotten any from him, but remember seeing those on his site. I tripped on the ones that I have, while looking for something else on eBay. For the price i grabbed them up.
          Don
          Kankakee IL

          Comment


            #6
            Ok, nother question/
            I have a Kohler/Carter #22 off of a k181. I haven't looked at Zach's site recently but as I remember, the smaller carbs have a smaller diameter thread main jet. Like 5/16" instead of 3/8". I need one.anyone have?
            oh yeah/ I forgot those are the pressed in ones that nobody can get. So this carb body might be junk. I recently dug it out while I was looking for something else, and forgot why it was still sitting in pieces.
            Don
            Kankakee IL

            Comment

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