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SINGLE CARB MOD

Discussion in 'XJ Modifications' started by Zookie400, Mar 14, 2011.

  1. Zookie400

    Zookie400 Active Member

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    well i said i was going to do it, and my rack of 4 CV carbs acted up on the way home from storage today so........

    i started making an intake manifold, i have a take-off harley carb. its a side draft keihin, single bore, throttle plate, pumper carb. i have not looked up the numbers to see exactly what it is yet but i will post up once i figure it out.

    this will unfortunately be a LOOOONNNG project because i just do not have much time to do anything on the bike, quad, truck, or mustang lately because we are working in long island. i am home weekends but i just dont have enough hours in a day. at $4 per gallon for diesel i will need to make some time, because 5mpg on the bike saves me some cash.

    discuss. 8)
     
  2. wizard

    wizard Active Member

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    Is that 5 mpg or 50 ?
     
  3. Orange-n-Black

    Orange-n-Black Well-Known Member

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    What's your ideas for the intake? Someone on this site said that they had done this but took a long time to get the intake right. All the port tubes had to be the same length if I remember correctly. :roll:
     
  4. Zookie400

    Zookie400 Active Member

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    eek! 50mpg!!! if it only got 5, i would have to scrap it!

    as for the intake....

    let me start by saying, this is not going to be for performance. this is primarily to RETAIN or IMPROVE the 50mpg it currently gets while eliminating a ridiculous rack of 4 cv carbs.

    with that being said, i have a few designs for intake manifold that all attempt to keep the runners as close to equal length as possible. the better ones may not fit, so i need to do some mach up and see what works and what doesnt. i also do not think equal runner length is going to be quite as important as it would be if i were doing to do this for performance reasons. just thinking "aloud" here, but if we pry away from the MC world of thinking, and look at some auto inline engines...even the performance offenhauser manifolds do not have equal runner length. only the most "extreme" high rpm full race engines have manifold designs aimed at equalizing runner length.

    one design that i keep coming back to resembles a 5.0ho style upper manifold or as some gm guys like to call them, a tunnel ram. the only thing i dont like about this design is i do not think i can keep the runners long enough. it would help if i had the bike here in my hotel room so i could see how much room i actually have.

    for those inbterested, i have not molested my cv rack yet, because if this fails i will tear into the rack, fix it and get the bike on the road for summer while i do some more in depth R&D so i can take a better and more prepared "swing" at it next winter. :)
     
  5. iwingameover

    iwingameover Active Member

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    I think the tunnel ram idea is probably your best bet. I don't think it would need to be all that big and would allow you the most equal intake runners with the least amount of work.

    Then put a pod on it because you can!
     
  6. Orange-n-Black

    Orange-n-Black Well-Known Member

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    I think the difference will be downdraft principles (automotive) vs sidedraft principles (motorcycle). That was my thinking on the manner but I might be wrong. There was some cool 4cyl. car manifolds designs from the past that could work, like the 240z Datsun/Nissan, that goes back a ways but I hope your getting the picture. And by all means put some pods on it.LOL
     
  7. hardlucktx

    hardlucktx Member

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    Weber makes some side draft intakes you might look at them for ideas. A buddy of mine had a two carb side draft intake on his pinto back in the early 80's.
     
  8. Bobe7316

    Bobe7316 Member

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    2into1 carb setup on a XS650 Yamaha


    [​IMG]
     
  9. BillB

    BillB Active Member

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  10. Erman

    Erman Member

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    I had a look at the image you linked to..

    Will there be a delay for the mixture to get to carbs 1&4 with this setup, or is it compensated for by using different diameter on the outer ports?
     
  11. darkfibre

    darkfibre Member

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    This style of manifold was common on cars in the 1960s. Not that efficient, but will certainly work.
     
  12. Orange-n-Black

    Orange-n-Black Well-Known Member

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    That is exactly what I was getting at (not that efficient), getting all the tubes to deliver the right mixture will be difficult. Hope it works out for you, keep us updated.
     
  13. sheafer

    sheafer New Member

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    [​IMG] i am attempting to use a holley 2bble. will use copper 1 /2 copper pipe from carb adapter plate to middle of homemade aluminum intake.[​IMG]
     
  14. BillB

    BillB Active Member

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    Id like to see the mpg with this.
     
  15. Zookie400

    Zookie400 Active Member

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    i wanted to use a 390 4bbl i had, but it got used for a truck instead. the only problem i saw with using a holly was the physical size of the thing! i would be very interested in seeing how yours comes out!

    i just walked in my door, back from LI. tomorrow i have a long list of things i need to do but i hope to work on the manifold. i am going to trial the tunnel ram style first.
     
  16. sheafer

    sheafer New Member

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    i think a 4bble would be overkill. ditto on how yours turns out. good luck
     
  17. sheafer

    sheafer New Member

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    cb550 with updraft tractor carb[​IMG]
     
  18. Zookie400

    Zookie400 Active Member

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    ok so its a Keihin butterfly non-cv for harley davidson. i cannot seem to find any info on a real model name for it (FCR for example) but all over harley forums thats how it is recognized. good enough i guess.

    the number on it is 27029-83D, so its the 4th version of the carb that was used in 1983 on basically all of the bikes. the harley guys claim that this carb is where the term "Keihin cough" originated, because of the super lean jetting and elimination of a check valve in the pump for epa compliance. the part number still doesnt tell me the advertised size of the carb.

    now i am going to measure it and scavenge materials for an intake.
     
  19. Zookie400

    Zookie400 Active Member

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    41 or 42mm carb, cannot be 100% accurate with my "home" set of calipers. they are very old and sloppy. close enough to kill my curiosity though.
     
  20. Zookie400

    Zookie400 Active Member

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    i started fabbing a manifold. i am going to tack this up, and see where i can put the carb, i want to make another runner that feeds the carb charge into the center (between 2 and 3) to keep the distances as close as possible.

    not much to look at, 5 minutes only gets you so far :lol:

    [​IMG]
     

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