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mikuni vacuum pump fuelling issue fix

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    mikuni vacuum pump fuelling issue fix

    I fitted the mikuni vacuum pump and came across the fuelling issue at higher speeds that a few other people seem to have had.
    My pump is just cable tied to the top frame spar, and it was plumbed into the rear cylinder.
    I flipped the pump over and routed it to the front cylinder, halving the length of the vacuum line - instant fix.
    It appears that the excess length of the line was sapping power and not feeding the pump properly.
    I hope this can help someone

    #2
    IN my experience, depending on the tubing used it wasn't the length so much but the ability of the vacuum tube to resist collapsing. I also noticed if you use one of the really short nipples that it can kind of peel back on the edge at speed and cause an air gap between the nipple and the tubing, especially if you have a lengthy piece of tubing and it would cause a vacuum leak. I just solved it buy putting a couple of zip ties on it to provide positive engagement. Once I did that it seems to have resolved the issue.
    88 Blue Hawk GT - Under construction but rideable (guest approved)
    89 BlackHawk 2.0 - On the lift and being assembled
    90 Hawk GT (color as to yet be determined) - Still on the shelf in crates

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      #3
      This makes sense, I will look into getting more suitable vacuum tube but for now I am stoked to have my bike running properly after too long limping around.
      Image IMG-20200513-134110465-HDR hosted in ImgBB

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        #4
        Originally Posted by Mk2 View Post
        This makes sense, I will look into getting more suitable vacuum tube but for now I am stoked to have my bike running properly after too long limping around.
        Rock on dude. Glad you got it figured out.

        Did you look into WW's mikuni mount? Nice little part if you are using that pump.
        Don't spend money and buy, spend time and learn.

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          #5
          WW mikuni mount is high on my list of future upgrades, as well as anything else I can afford to get from him.
          I'm UK based and currently out of work so making do at the moment.
          I was lucky enough to get a chain adjuster tool and rear brake torsion bar a few years ago which is probably my favourite thing on the bike. I also managed to find a Hord collector from a UK member I forget the name of.
          When money flowed easier I got a nitron shock, quickly followed by a chain roller from.. frinessi? Aswell as a tail fairing and passenger seat cowl that Fabian actually dropped off in my front garden when he was passing through England, although those are awaiting paint.
          I love this bike so much
          Free image hosting and sharing service, upload pictures, photo host. Offers integration solutions for uploading images to forums.

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            #6
            Hmm maybe this link will work
            Some of the parts I've accumulated

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              #7
              Originally Posted by Mk2 View Post
              Hmm maybe this link will work
              That worked.

              Some nice stuff there.

              Having done a few hawks just soup to nuts right out the gate, I have to say that the most fun way to do it is to go bit by bit.

              Ride it as it comes together. It's fun. You can see and feel the change each mod makes.

              Eventually you look back and are like, damn, a lot has changed!

              Do you have any of the "cheapish" other mods? Braided front line and fork springs can definitely change the feel of the bike and if you get lucky you can probably get them used for $50 for the springs and $25 for a line.

              My favorite changes are the free ones. Well mostly free. Cleaning, greasing, taking systems apart and putting them back together.. very satisfying, mostly free outside of maybe some gas, a brush, some grease and some brake clean.


              Fun to see the bike progress. Keep up the nice work sir!
              Don't spend money and buy, spend time and learn.

              Comment


                #8
                Thicker wall thickness is the key to looking for a good vacuum line FWIW. Should be pretty cheap by the foot or so in a auto parts store.
                88 Blue Hawk GT - Under construction but rideable (guest approved)
                89 BlackHawk 2.0 - On the lift and being assembled
                90 Hawk GT (color as to yet be determined) - Still on the shelf in crates

                Comment

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