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  1. #1

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    OS 61 sf max carb problem

    I am running an OS61SF max on a TT fun fly extra. I got it used. The low speed needle is adjusted by an eccentric screw moving a fork. The fork was upside down (I think). There is a crescent cut out on the closed end of the fork. Does that face the high spd needle valve?
    I replaced the needle which was broken off flat. I use a pitts muffler, and cannot seem to get a smoke trail, even when it seems too rich.
    Oh, I am running a 11x7.5 prop. I posted in fun fly to ask if that is enough prop.
    Thanks,
    Tom

  2. #2

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    OS 61 sf max carb problem

    Sorry, That doesn't sound like a stock carb to me. A stock carb should have the low speed needle on the throttle arm side right in the center of the barrel. the high speed needle is on the other side of the carb. I don't beleive I have ever seen a "fork" on a carb.....you sure have me stumped.
    Who Said Maturity Comes With Age?

    Danny Mercer
    AMA566237

  3. #3
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    Is that the O.S. Type 7L carb ?

    It goes like this.....
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    An engineer says.... "That will not work".
    A mechanic says..."Oh yeah, watch this".
    Old age and treachery will overcome youth and skill.
    Revver Bro #4.

  4. #4

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    yeehaa!

    Yep, that is the one. Your picture makes it clear the cut out is toward the needle. Thanks a heap!
    Tom

  5. #5
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    OS 61 sf max carb problem

    Flyboy Dave,

    The main thing about your carb is the position of the slotted screw with the eccentric head. That's the one at the top of the picture. When the slot in the screw is straight up and down, your idle mixture is in the center of its range. Turning it clockwise will lean the idle mixture, and turning is counter-clockwise will richen the idle mixture.

    If the carb's been disassembled, the mixture control assembly may have been installed at 180 degrees to the correct position. This will cause all kinds of headaches in running.

    If your engine will throttle nicely from idle to top RPM, and has a good idle, then the assembly's installed correctly.

    A smoke trail may or may not develop when the engine's running well. It depends upon the fuel used, the exhaust system, and the weather. You can have an engine running very well with little visible smoke. Depending upon the fuel, you can have a lot of visible smoke and still be running too lean.

    Listen to the engine carefully, do the 'pinch' test while setting the engine. If you give the fuel line a quick pinch at full throttle and the RPM jumps a bit, you're rich of peak RPM. If it sags or stays the same, you need to richen the high-speed needle until you get a slight jump. Listen to the engine carefully when it's in the air, and adjust the mixture as necessary to allow for the RPM increase as the engine unloads.

    We usually ran the O.S. Max .61 SF engines on our test stand with a 12x8 APC prop, 10% Omega Fuel, stock muffler, and an O.S. #8 plug. We'd see RPM in the mid- to high-11,000's. Any idle below about 2,700-2,800 was considered 'good'.
    Bill Baxter, Manager Hobby Services/Futaba Service/North America
    3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
    Service Phone: 217 398-0007
    Email: hobbyservices@hobbico.com

  6. #6
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    onrecess....If you don't mind...

    ....I'll E-mail you the "Operating Instructions for the
    O.S. Type 7L carb ".

    E-mail, or PM me your E-mail Addy, so I can attach
    the instructions.

    Dave.

    ( Thanks, Bill....that's all good info )
    An engineer says.... "That will not work".
    A mechanic says..."Oh yeah, watch this".
    Old age and treachery will overcome youth and skill.
    Revver Bro #4.

  7. #7

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    7 l carb

    hey flyboy, i would love it if u cound send me something to show me how to set the 7l carb. my e-mail addy is nowellracing@yahoo.com. thanks alot.

  8. #8
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    aou816....

    ....OK....I saw them just the other day....I'll scan 'em,
    and e-mail 'em to ya'....
    An engineer says.... "That will not work".
    A mechanic says..."Oh yeah, watch this".
    Old age and treachery will overcome youth and skill.
    Revver Bro #4.

  9. #9
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    aou816....

    ....they're on the way....

    Dave.
    An engineer says.... "That will not work".
    A mechanic says..."Oh yeah, watch this".
    Old age and treachery will overcome youth and skill.
    Revver Bro #4.


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