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Thread: Sidedraft woes..

  1. #1
    Senior Member
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    Aug 2010
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    Sidedraft woes..

    So my fb is finally running and driving with the mikuni 44 side draft that I bought last summer, however I have a few issues.. At WOT, near 6000 rpm the motor acts like it's starved for fuel, it gets to redline a little slower than I think is normal. I am running between 3.4 and 4 psi of fuel pressure. Also, I have the OMP hooked up and didn't think it was working, but one of the lines keeps falling off the carb and I find motor oil drops on the intake manifold, but I see no oil coming up from the OMP lines, any ideas? Does the OMP have one return and one feed line, or are they both feed? I know I have to replace the accelerator pump b/c the car bogs with a quick foot on the throttle off idle, but otherwise it revs nicely till the aforementioned 6000 rpm or so.. Does anyone have any tips to make the Mikuni get along a little better with my 12a?

  2. #2
    Member
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    Oct 2007
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    Hope, British Columbia, Canada
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    55

    Re: Sidedraft woes..

    Your main jets maybe a tad too small. Starving it of fuel.

    What size chokes are you running?

  3. #3
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    Jan 2008
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    Southeastern Massachusetts
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    Re: Sidedraft woes..

    The oil lines are both feeds.

  4. #4
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    Re: Sidedraft woes..

    Drove the car again tonight, omp lines are secure but still getting oil on manifold.. Car pulls nice and strong at lower rpm but breaks up and loses power above 5000.. Carb specs will be posted as soon as I tear it apart to clean it but I think it is the original killer bee aggressor setup from rotary reliability and racing..

  5. #5
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    May 2008
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    Austin, TX
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    Re: Sidedraft woes..

    I agree with the above post, a bigger main jet might solve your problem.

  6. #6
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    Re: Sidedraft woes..

    Does anyone know where to order parts for this carb in the states? I definitely need an accelerator pump and probably jets..

  7. #7
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    Aug 2011
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    norcal
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    Re: Sidedraft woes..

    Is the motor ported ? A easy way to make omp lines that dont leak is : use high quality German vacume line with the cloth braid outer sheathing , the stock mazda omp lines are made of brittle plastic that has went through tons of heat cycling and rubber hose ends that are usually worn out.

  8. #8
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    Re: Sidedraft woes..

    The motor is not ported, I will surely look into replacing the lines with the German stuff.. Thanks!

  9. #9
    Junior Member
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    Oct 2011
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    Bay Area
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    13

    Re: Sidedraft woes..

    Hi oldisgold, this "Car pulls nice and strong at lower rpm but breaks up and loses power above 5000" sounds like detonation. How is your timing?
    You could put your fuel pressure gauge on a hose and tape it to the outside of the windshield to see if you are losing fuel pressure above 5k. Be sure to secure the hose on your regulator and the gauge because if it pops off under pressure you will have a fire.

  10. #10
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    Re: Sidedraft woes..

    We tuned the car a bit the other day and adjusted the timing and mixture screws.. the car runs a LOT better than before but still breaks up noticeably after 5500 to 6000 rpm and on to redline, though this is only noticeable in 1st gear pulls. For some reason, it sounds fine all the way to redline in 2nd and 3rd gears.. Does this make sense? I'm thinking it isn't getting enough fuel, so either the regulator is not allowing enough at WOT or the main jets are too small, good idea holding the fuel pressure gauge up to the windshield, I'll try that when we tune again, which will be when the weather clears. Still need to find an accelerator pump and probably a jetting kit, who knows of a good source for mikuni parts?

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